1. Nutrients and Their Functions

 

 

 

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What Is a Nutrient?

A nutrient is a substance needed by the body for normal growth, repair, metabolism, and health.

Food does much more than simply provide energy.

The body requires nutrients to:

• release energy
• build new tissues
• repair damaged tissues
• produce enzymes and other molecules
• maintain bones and teeth
• transport substances
• regulate chemical reactions
• maintain fluid balance
• support the nervous and immune systems

The major nutrient groups we will study are:

carbohydrates, lipids, proteins, vitamins, minerals, and water.

Why Do We Need Different Nutrients?

No single nutrient performs every function required by the body.

Carbohydrates are particularly important as an energy source.

Proteins provide amino acids needed to build and repair tissues.

Lipids provide concentrated energy storage and are important components of cell membranes.

Vitamins and minerals support many metabolic and structural functions.

Water provides the environment in which much of the body's chemistry occurs.

Therefore, good nutrition requires an appropriate combination of nutrients.

The Six Major Nutrient Groups

These nutrients are needed in different amounts.

This leads to an important distinction:

macronutrients

and:

micronutrients

Macronutrients

Macronutrients are nutrients required in relatively large amounts.

The main energy-yielding macronutrients are:

• carbohydrates
• proteins
• lipids

Water is also required in large amounts, although it does not provide energy.

 

 

 

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The prefix macro- means:

large

This refers to the amount needed, not the size of the nutrient molecule.

Micronutrients

Micronutrients are required in much smaller quantities.

They include:

• vitamins
• minerals

 

 

 

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The prefix micro- means:

small

Again, this refers to the quantity needed.

Small amounts do not mean they are unimportant.

A deficiency of a particular vitamin or mineral can cause serious health problems.

Macronutrients vs Micronutrients

Both groups are essential for health.

Carbohydrates

Carbohydrates are an important source of energy for the body.

Foods rich in carbohydrates include:

• bread
• rice
• pasta
• potatoes
• cereals
• fruits
• grains

 

 

 

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Carbohydrates include sugars, starches, and dietary fibre.

Carbohydrates and Energy

Many dietary carbohydrates are digested into:

glucose

Glucose can then be absorbed into the bloodstream and transported to cells.

Cells use glucose during cellular respiration.

A simplified equation for aerobic respiration is:

glucose + oxygen → carbon dioxide + water + energy transferred

The released energy supports processes throughout the body.

What Uses the Energy?

Energy released through respiration is needed for:

• muscle contraction
• active transport
• protein synthesis
• cell division
• growth
• transmission of nerve impulses
• maintaining body temperature

Therefore, carbohydrate intake is closely connected to cellular activity.

Starch

Starch is a complex carbohydrate found in foods such as:

• rice
• potatoes
• bread
• pasta
• cereals

Starch consists of many glucose units joined together.

During digestion:

starch → smaller sugars → glucose

 

 

 

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Enzymes such as amylase are involved in starch digestion.

Sugars

Sugars are smaller carbohydrates.

Examples include:

• glucose
• fructose
• sucrose
• lactose

Some sugars occur naturally in foods such as fruits and milk.

Others are added to processed foods and drinks.

Sugars can provide energy, but diets consistently high in added sugars can contribute to health problems, especially when overall energy intake exceeds the body's needs.

Dietary Fibre

Dietary fibre consists largely of plant carbohydrates that human digestive enzymes cannot fully digest.

Sources include:

• whole grains
• vegetables
• fruits
• beans
• lentils

 

 

 

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Fibre contributes to healthy digestive function and can help support normal bowel movements.

Some types of fibre also provide substrates for microorganisms living in the large intestine.

Lipids

Lipids include fats and oils.

Important sources include:

• vegetable oils
• nuts
• seeds
• avocado
• dairy products
• fish
• meat

 

 

 

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Lipids have several important functions.

Lipids as Energy Stores

Lipids are excellent long-term energy stores.

Gram for gram, lipids contain more chemical energy than carbohydrates or proteins.

Excess energy can be stored in the body as fat.

When energy is required, stored lipids can be mobilized and used in metabolism.

This makes lipids important for:

long-term energy storage

Lipids and Cell Membranes

Cell membranes contain large amounts of:

phospholipids

Phospholipids form the basic structure of the cell membrane.

 

 

 

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Therefore, lipids are not simply energy stores.

They are fundamental structural components of every cell.

Other Functions of Lipids

Lipids are also involved in:

• thermal insulation
• cushioning and protection of organs
• production of some hormones
• absorption of fat-soluble vitamins
• formation of cell membranes
• energy storage

Fat-soluble vitamins include:

A, D, E and K

Some dietary lipid is therefore necessary for normal health.

Saturated and Unsaturated Fats

Dietary fats contain different types of fatty acids.

Saturated fats contain fatty acids without carbon-carbon double bonds.

Unsaturated fats contain one or more carbon-carbon double bonds.

 

 

 

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Different types and amounts of dietary fat can have different effects on health.

Nutrition therefore involves both:

how much fat is consumed

and:

which types of fat are consumed.

Proteins

Proteins are large molecules made from:

amino acids

Protein-rich foods include:

• meat
• fish
• eggs
• dairy products
• beans
• lentils
• soy products
• nuts

 

 

 

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Proteins perform an enormous variety of functions in the body.

Proteins for Growth and Repair

One of the best-known functions of protein is:

growth and tissue repair

The body constantly replaces and repairs cells.

Protein is needed to build:

• muscle tissue
• skin
• connective tissues
• many cellular structures

Protein is particularly important during periods of:

• growth
• recovery
• tissue repair

Proteins Are More Than Muscles

Proteins perform many other roles.

Examples include:

Enzymes

Most enzymes are proteins.

Antibodies

Many immune-system molecules are proteins.

Transport proteins

Haemoglobin is a protein involved in oxygen transport.

Structural proteins

Collagen contributes to connective tissues.

Some hormones

Some signaling molecules are proteins or peptides.

 

 

 

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Amino Acids

During digestion:

proteins → peptides → amino acids

Amino acids are absorbed through the small intestine and transported around the body.

Cells can then rearrange these amino acids to build the proteins they require.

Some amino acids can be produced by the human body.

Others must be obtained through the diet and are called:

essential amino acids

Protein and Energy

Proteins can also be used as an energy source.

However, providing energy is not their only or primary biological role.

Proteins are especially important as:

structural and functional materials

The body generally benefits from using carbohydrates and lipids as major energy sources while retaining amino acids for protein synthesis and other functions.

Vitamins

Vitamins are organic compounds required in relatively small amounts for normal health and metabolism.

They do not generally provide energy directly.

Instead, they support many body processes.

 

 

 

Important vitamins include:

• vitamin A
• B vitamins
• vitamin C
• vitamin D
• vitamin E
• vitamin K

Each has different functions.

Vitamin A

Vitamin A is important for:

• normal vision
• immune function
• maintenance of epithelial tissues
• normal growth and development

Sources include foods such as:

• liver
• eggs
• dairy products
• carrots
• sweet potatoes
• dark green vegetables

Plant foods often contain compounds such as beta-carotene that the body can convert into vitamin A.

Vitamin B Group

The B vitamins include several different compounds.

They play important roles in:

• energy metabolism
• nervous-system function
• red blood cell formation
• DNA-related processes

Sources include:

• whole grains
• meat
• eggs
• dairy products
• legumes
• leafy vegetables

Different B vitamins have different functions, so they should not be treated as one single substance.

Vitamin C

Vitamin C is important for:

• collagen production
• wound healing
• antioxidant functions
• supporting normal immune function
• helping absorption of non-haem iron

 

 

 

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Sources include:

• citrus fruits
• peppers
• strawberries
• broccoli
• many other fruits and vegetables

Severe vitamin C deficiency can cause:

scurvy

Vitamin D

Vitamin D is important for maintaining normal calcium and phosphate balance.

It therefore contributes to:

healthy bones and teeth

The body can produce vitamin D in the skin when exposed to sufficient ultraviolet B radiation from sunlight.

Vitamin D can also come from dietary sources and fortified foods.

 

 

 

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Severe deficiency in growing children can contribute to:

rickets

Minerals

Minerals are inorganic nutrients needed for various body functions.

Important dietary minerals include:

• calcium
• iron
• sodium
• potassium
• magnesium
• phosphorus
• iodine

Like vitamins, minerals are required in relatively small amounts compared with major macronutrients.

However, their functions are essential.

Calcium

Calcium is important for:

• bones
• teeth
• muscle contraction
• nerve function
• blood clotting

Sources include:

• dairy products
• some leafy vegetables
• calcium-fortified foods
• some fish
• certain seeds and nuts

 

 

 

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Calcium works together with other nutrients, including vitamin D, in maintaining bone health.

Iron

Iron is particularly important because it is part of:

haemoglobin

Haemoglobin is found in red blood cells and binds oxygen.

Therefore:

iron → haemoglobin → oxygen transport

 

 

 

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Sources of iron include:

• meat
• beans
• lentils
• fortified cereals
• leafy green vegetables

Insufficient available iron can contribute to iron-deficiency anaemia.

Sodium and Potassium

Sodium and potassium are important electrolytes.

They contribute to:

• nerve impulses
• muscle function
• fluid balance
• normal cellular function

The body requires these minerals, but the amounts must remain within suitable ranges.

This illustrates an important principle:

essential does not mean unlimited amounts are beneficial.

Iodine

Iodine is needed for the production of:

thyroid hormones

Thyroid hormones help regulate metabolism, growth, and development.

Dietary sources can include:

• iodized salt
• seafood
• dairy products
• other foods depending on local food production

Severe iodine deficiency can interfere with normal thyroid function.

Water

Water is sometimes overlooked because it does not provide energy.

However, water is essential for life.

A large proportion of the human body consists of water.

 

 

 

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Water has several major functions.

Water as a Solvent

Many substances dissolve in water.

This makes water an excellent medium for:

• chemical reactions
• transport of nutrients
• transport of waste
• cellular metabolism

The cytoplasm inside cells contains large amounts of water.

Many biochemical reactions therefore occur in aqueous environments.

Water and Transport

Blood plasma contains a large amount of water.

Water helps transport:

• glucose
• amino acids
• hormones
• ions
• carbon dioxide
• waste products

around the body.

Therefore, water is directly connected to the circulatory system.

Water and Temperature Regulation

Water has important thermal properties.

The body can use sweating to help regulate temperature.

 

 

 

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When sweat evaporates from the skin:

thermal energy is transferred away from the body

This helps cool the body during:

• exercise
• hot weather
• other conditions that increase body temperature

Water in Chemical Reactions

Water also participates directly in chemical reactions.

For example, digestive enzymes often catalyze:

hydrolysis reactions

Hydrolysis uses water to break larger molecules into smaller molecules.

Therefore, water is both:

a reaction medium

and sometimes:

a reactant

Connecting Nutrients to Body Processes

Nutrients do not work independently.

They contribute to interconnected body processes.

For example:

Carbohydrates → glucose → cellular respiration → energy transfer

Proteins → amino acids → protein synthesis → growth and repair

Lipids → phospholipids → cell membranes

Iron → haemoglobin → oxygen transport

Vitamin D + calcium → bone health

Water → blood plasma → transport

These relationships are more useful than simply memorizing lists.

Nutrients and Cellular Respiration

Cells need energy for their activities.

Glucose obtained from carbohydrates is commonly used in aerobic respiration:

glucose + oxygen → carbon dioxide + water

Energy transferred during respiration can then support:

• movement
• growth
• repair
• active transport
• nerve signaling
• synthesis of molecules

 

 

 

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Nutrients and Growth

Growth requires more than energy.

New cells need:

• proteins
• lipids
• minerals
• vitamins
• water
• energy

For example, building new muscle tissue requires amino acids from protein.

Building new cell membranes requires lipids.

Producing DNA and other molecules requires many nutrients and energy.

Growth is therefore supported by the diet as a whole.

Nutrients and Blood

Several nutrients contribute to normal blood function.

For example:

Iron

is required for haemoglobin.

Protein

provides amino acids needed for many blood proteins.

Water

forms much of blood plasma.

Vitamins and minerals

support blood-cell production and clotting processes.

 

 

 

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Nutrients and Bones

Healthy bones depend on several factors.

Two important nutrients are:

calcium

and:

vitamin D

Calcium contributes to bone mineral structure.

Vitamin D supports calcium absorption and regulation.

Protein and other minerals are also important components of healthy bone tissue.

Therefore, bone health depends on more than one nutrient.

Nutrients and the Nervous System

The nervous system also depends on nutrients.

Examples include:

Glucose

provides an important fuel source.

Sodium and potassium

are essential for electrical signaling in nerves.

Lipids

are important components of cell membranes and myelin.

B vitamins

support several aspects of nervous-system metabolism.

Nutrient functions therefore extend throughout the body.

Nutrient Deficiency

A deficiency occurs when the body does not obtain or absorb enough of a required nutrient over time.

Examples include:

Deficiency diseases demonstrate why micronutrients can be essential even though they are needed in small amounts.

More Is Not Always Better

An important principle in nutrition is:

A nutrient can be essential without unlimited intake being beneficial.

The body requires nutrients within appropriate ranges.

Too little can cause deficiency.

Too much of some nutrients can also cause health problems.

For example, excessive intake of some vitamins and minerals can be harmful.

Nutrition is therefore about:

balance and appropriate amounts

rather than simply maximizing every nutrient.

Energy from Macronutrients

Carbohydrates, proteins, and lipids can all provide energy.

Approximate energy values are:

Carbohydrate: 4 kcal per gram

Protein: 4 kcal per gram

Fat: 9 kcal per gram

This explains why fat is described as a concentrated energy source.

It provides more than twice as much energy per gram as carbohydrate or protein.

Do Vitamins Provide Energy?

No.

Vitamins do not directly provide usable food energy in the way carbohydrates, proteins, and lipids do.

However, many vitamins are essential for reactions involved in:

energy metabolism

This distinction is important.

A vitamin may help the body process nutrients without itself serving as a significant energy source.

Do Minerals Provide Energy?

Minerals also do not provide energy.

Iron does not "give" the body energy.

Instead:

iron is needed for haemoglobin → haemoglobin transports oxygen → oxygen supports aerobic respiration

A person with insufficient iron may feel tired partly because oxygen transport can be impaired.

But iron itself is not an energy-containing fuel.

Water Does Not Provide Energy Either

Water contains no food energy.

Yet a person cannot survive without it.

This demonstrates that:

nutritional importance is not determined only by energy content.

Some of the body's most essential nutrients provide no calories at all.

A Balanced Diet

A balanced diet provides appropriate amounts and varieties of nutrients needed by the body.

 

 

 

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A balanced eating pattern generally includes a variety of:

• vegetables
• fruits
• whole grains and other carbohydrate sources
• protein-rich foods
• sources of beneficial fats
• appropriate fluids

Variety helps provide different vitamins, minerals, amino acids, fatty acids, and other beneficial food components.

Nutrient Density

Foods can also be considered in terms of nutrient density.

A nutrient-dense food provides substantial amounts of useful nutrients relative to its energy content.

Examples can include:

• vegetables
• fruits
• legumes
• eggs
• fish
• whole grains
• nuts and seeds

This concept helps explain why simply counting calories does not provide a complete picture of nutrition.

Reading Nutrition Information

Food labels often provide information about:

• energy
• carbohydrates
• sugars
• protein
• total fat
• saturated fat
• sodium
• fibre
• selected vitamins and minerals

 

 

 

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When comparing foods, it is important to consider the stated:

serving size

or:

amount per 100 g

Otherwise, comparisons may be misleading.

Example: Breakfast

Consider a breakfast containing:

• oatmeal
• milk or fortified alternative
• banana
• nuts
• water

Different foods contribute different nutrients.

Oatmeal

Carbohydrates, fibre, some protein and minerals.

Milk

Protein, carbohydrates, calcium and other nutrients.

Banana

Carbohydrates, potassium and vitamins.

Nuts

Lipids, protein, minerals and vitamins.

Water

Hydration.

A meal can therefore supply many nutrients simultaneously.

Example: Exercise

Imagine someone running.

Their body requires:

carbohydrates and lipids

to provide metabolic fuel.

oxygen

for aerobic respiration.

water

for transport and temperature regulation.

sodium and potassium

for nerve and muscle function.

proteins

for ongoing tissue maintenance and repair.

 

 

 

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No single nutrient supports the entire process.

Example: Healing a Cut

Repairing damaged tissue requires:

• amino acids from proteins
• energy
• vitamin C for normal collagen synthesis
• minerals
• water
• many other nutrients

This demonstrates how nutrients work together.

A single body process may depend on several nutrient groups.

Macronutrient or Micronutrient?

Classify each:

Carbohydrate → macronutrient

Protein → macronutrient

Lipid → macronutrient

Vitamin C → micronutrient

Iron → micronutrient

Calcium → micronutrient

Water is required in large amounts but is usually discussed separately because it does not provide energy.

Organic and Inorganic Nutrients

Nutrients can also be classified chemically.

Organic nutrients include carbon-containing biological molecules such as:

• carbohydrates
• lipids
• proteins
• vitamins

Inorganic nutrients include:

• minerals
• water

This is a chemical classification and is different from the macronutrient/micronutrient classification.

Nutrients Work Together

Consider oxygen transport.

Iron is required for haemoglobin.

Protein provides amino acids needed to produce haemoglobin's protein components.

Several vitamins support normal blood-cell formation.

Water forms much of the plasma through which blood cells travel.

Therefore:

one biological function often depends on several nutrients working together.

This is why nutrition should be understood as a system rather than as isolated nutrient lists.

Common Misconception: Carbohydrates Are Unnecessary

Carbohydrates are an important source of energy in many diets.

Foods containing carbohydrates can also provide:

• fibre
• vitamins
• minerals
• other useful compounds

The nutritional effects depend on the type, amount, and overall dietary pattern.

Common Misconception: All Fat Is Bad

The body requires lipids.

Lipids are needed for:

• cell membranes
• energy storage
• insulation
• absorption of fat-soluble vitamins
• production of certain signaling molecules

The important considerations include:

type + amount + overall diet

rather than simply avoiding all fat.

Common Misconception: Protein Is Only for Muscles

Protein is required throughout the body.

Proteins function as:

• enzymes
• antibodies
• receptors
• transport molecules
• structural materials
• some hormones

Muscle is only one example.

Common Misconception: Vitamins Give You Energy

Vitamins support metabolism but do not directly provide calories.

The major energy-yielding nutrients are:

carbohydrates

lipids

and:

proteins

Common Misconception: Micronutrients Are Less Important

"Micro" refers to the amount required.

It does not mean:

less important

Iron is needed only in relatively small quantities, but insufficient iron can seriously affect oxygen transport.

Vitamin D is needed in relatively small amounts, but it is important for calcium regulation and bone health.

Common Misconception: Water Is Not a Nutrient

Water is an essential nutrient.

It is required for:

• transport
• chemical reactions
• temperature regulation
• maintaining blood volume
• cellular function

Humans can survive much longer without food than without adequate water.

Comparing the Nutrients

Connecting Nutrition to Digestion

The nutrients we eat must often be processed before they can be absorbed.

For example:

starch

↓

amylase and other enzymes

↓

glucose

protein

↓

proteases

↓

amino acids

lipid

↓

lipases

↓

smaller lipid components

 

 

 

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The products can then be absorbed through the small intestine and transported to cells.

Connecting Nutrition to the Circulatory System

After absorption, nutrients must reach cells.

The circulatory system transports substances such as:

• glucose
• amino acids
• vitamins
• minerals
• water

Lipid transport also involves the lymphatic system before many lipid products enter the bloodstream.

This gives us the sequence:

food → digestion → absorption → transport → cells

Connecting Nutrition to Cells

Ultimately, nutrition is about supplying cells with the substances they need.

Cells use nutrients to:

• release energy
• build membranes
• produce proteins
• copy DNA
• maintain ion concentrations
• carry out chemical reactions
• grow
• divide
• repair damage

Nutrition therefore connects directly to nearly every area of biology.

Did You Know?

Your body continually rebuilds itself.

 

 

 

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Cells die and are replaced.

Proteins are broken down and rebuilt.

Cell membranes are repaired.

Blood cells are continually produced.

Bones are constantly remodeled.

The materials needed for these processes ultimately come from nutrients obtained through food and water.

Nutrition is therefore not simply about "fuel."

It supplies both:

energy

and:

the raw materials needed to build and maintain the body.

Key Terms

• Nutrient: Substance required for normal growth, metabolism and health.
• Macronutrient: Nutrient required in relatively large amounts.
• Micronutrient: Nutrient required in relatively small amounts.
• Carbohydrate: Nutrient group that includes sugars, starches and fibre.
• Glucose: Simple sugar commonly used in cellular respiration.
• Dietary fibre: Plant-derived carbohydrate material not fully digested by human enzymes.
• Lipid: Group including fats and oils, important for energy storage and cell membranes.
• Protein: Molecule made from amino acids with structural and functional roles.
• Amino acid: Building block of proteins.
• Essential amino acid: Amino acid that must be obtained adequately from the diet.
• Vitamin: Organic micronutrient needed for normal biological functions.
• Mineral: Inorganic nutrient element required for body functions.
• Calcium: Mineral important for bones, muscles and other processes.
• Iron: Mineral required for haemoglobin and normal oxygen transport.
• Iodine: Mineral required for thyroid hormone production.
• Water: Essential nutrient serving as a solvent, transport medium and temperature regulator.
• Deficiency: Insufficient supply or availability of a required nutrient.
• Balanced diet: Dietary pattern providing appropriate amounts and varieties of nutrients.
• Nutrient density: Amount of useful nutrients supplied relative to energy content.
• Metabolism: All chemical reactions occurring within the body.

Key Relationships

Energy:

carbohydrates → glucose → respiration → energy transfer

Growth and repair:

protein → amino acids → new proteins

Cell membranes:

dietary nutrients → lipids → phospholipid membranes

Oxygen transport:

iron → haemoglobin → oxygen transport

Bone health:

calcium + vitamin D + other nutrients → healthy bone maintenance

Transport:

water → blood plasma → movement of substances

Overall:

food → nutrients → digestion → absorption → transport → cellular function

Key Takeaways

• Nutrients are substances needed for normal growth, repair, metabolism, and health.
• The major nutrient groups include carbohydrates, lipids, proteins, vitamins, minerals, and water.
• Different nutrients perform different functions.
• Macronutrients are required in relatively large amounts.
• Carbohydrates, proteins, and lipids are major macronutrients.
• Water is also required in large amounts but does not provide energy.
• Vitamins and minerals are micronutrients.
• Micronutrients are required in small amounts but are still essential.
• Carbohydrates are an important source of energy.
• Many carbohydrates are digested into glucose.
• Glucose can be used during cellular respiration.
• Dietary fibre supports normal digestive function.
• Lipids provide concentrated energy storage.
• Lipids are important components of cell membranes.
• Lipids also contribute to insulation, protection, and absorption of fat-soluble vitamins.
• Proteins are made from amino acids.
• Proteins are required for growth and tissue repair.
• Proteins also function as enzymes, antibodies, transport molecules, and structural materials.
• Vitamins support and regulate many biological processes.
• Vitamin C is important for normal collagen formation.
• Vitamin D contributes to calcium regulation and bone health.
• Minerals perform both structural and physiological functions.
• Calcium is important for bones, muscle contraction, nerve function, and other processes.
• Iron is required for haemoglobin and oxygen transport.
• Iodine is needed for thyroid hormone production.
• Sodium and potassium are important for nerve impulses, muscle function, and fluid balance.
• Water acts as a solvent and transport medium.
• Water is important for temperature regulation.
• Water participates in many chemical reactions.
• Carbohydrates, proteins, and fats can provide energy; vitamins, minerals, and water do not directly provide food energy.
• Nutrient deficiency can interfere with normal body function.
• More of an essential nutrient is not always better; appropriate amounts are important.
• Nutrients frequently work together rather than acting independently.
• A balanced diet provides a variety of nutrients in suitable amounts.
• Digestion converts large nutrient molecules into smaller molecules that can be absorbed.
• The circulatory system transports absorbed nutrients to cells.
• Nutrition provides both energy and the raw materials required to build, maintain, and regulate the human body.

2. Balanced Diets

 

 

 

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What Is a Balanced Diet?

A balanced diet provides the body with the energy and nutrients it needs in appropriate amounts.

A balanced diet should provide:

• carbohydrates
• proteins
• lipids
• vitamins
• minerals
• fibre
• water

Balance does not mean eating exactly the same foods every day.

Instead, it means eating a suitable variety and proportion of foods over time so that nutritional needs are met without consistently consuming too much or too little.

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Why Do We Need a Balanced Diet?

The human body carries out thousands of processes every day.

Cells need energy.

Muscles need fuel.

Tissues need materials for growth and repair.

Bones require minerals.

Enzymes and other proteins need amino acids.

Blood transports nutrients and gases.

The nervous system requires appropriate concentrations of ions.

All of these processes depend on nutrition.

A balanced diet therefore supports:

energy + growth + repair + regulation + health

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The Main Components

A healthy dietary pattern includes appropriate amounts of:

Carbohydrates

Important sources of energy and, depending on the food, fibre.

Proteins

Provide amino acids for growth, repair, enzymes and other proteins.

Lipids

Provide energy, essential fatty acids and materials for cell membranes.

Vitamins

Support many metabolic processes.

Minerals

Contribute to processes such as bone formation, oxygen transport and nerve function.

Water

Supports transport, chemical reactions and temperature regulation.

Fibre

Supports digestive health.

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Balance Is About Proportion

A balanced diet does not require equal amounts of every nutrient.

The body needs different nutrients in different quantities.

For example:

water

is required in relatively large quantities.

carbohydrates, fats and proteins

are macronutrients.

vitamins and minerals

are generally required in much smaller amounts.

However:

small amount needed ≠ unimportant

 

 

 

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Building a Balanced Meal

One useful approach is to divide a meal approximately into major food groups.

A simple visual model might emphasize:

about half: vegetables and fruits

about one quarter: whole grains or other carbohydrate-rich foods

about one quarter: protein-rich foods

with water as a common drink and moderate amounts of healthy fats.

This is a general planning model rather than a precise rule for every person or meal.

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Vegetables and Fruits

Vegetables and fruits can provide:

• vitamins
• minerals
• fibre
• water
• carbohydrates
• many other plant compounds

Examples include:

• leafy vegetables
• carrots
• tomatoes
• broccoli
• peppers
• berries
• apples
• oranges
• bananas

 

 

 

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Eating a variety helps provide a broader range of nutrients.

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Carbohydrate-Rich Foods

Carbohydrate-rich foods include:

• rice
• bread
• pasta
• oats
• potatoes
• corn
• other grains

Whole-grain versions often contain more fibre and retain more naturally occurring nutrients than highly refined alternatives.

Examples include:

• brown rice
• whole-grain bread
• oatmeal
• whole-grain pasta

Carbohydrates can ultimately supply glucose for cellular respiration.

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Protein-Rich Foods

Protein sources include:

• fish
• eggs
• poultry
• meat
• beans
• lentils
• tofu
• soy products
• dairy products
• nuts and seeds

 

 

 

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Protein supplies amino acids used for:

• growth
• tissue repair
• enzymes
• antibodies
• transport proteins
• many cellular structures

A balanced diet can include both plant and animal protein sources, depending on individual preferences and needs.

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Dietary Fats

Dietary fats are necessary for health.

They contribute to:

• cell membranes
• energy storage
• insulation
• essential fatty acids
• absorption of vitamins A, D, E and K
• production of some signaling molecules

Sources of unsaturated fats include:

• nuts
• seeds
• avocado
• fish
• many vegetable oils

 

 

 

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Balance involves considering both the amount and type of fat consumed.

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Fibre

Fibre is an important part of a balanced diet.

Good sources include:

• whole grains
• vegetables
• fruits
• beans
• lentils
• nuts and seeds

Fibre supports normal digestive function and bowel movements.

Some types of fibre also support microorganisms living in the large intestine.

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Water

A balanced diet also requires adequate fluid intake.

Water is required for:

• chemical reactions
• transport
• blood volume
• temperature regulation
• removal of waste
• normal cell function

 

 

 

5

Fluid needs vary depending on factors such as:

• activity
• temperature
• humidity
• body size
• diet
• pregnancy or breastfeeding
• illness

This is one reason nutritional needs cannot be identical for everyone.

---

Energy Balance

Food provides energy.

The body uses energy for:

• basal metabolism
• movement
• maintaining body temperature
• growth
• tissue repair
• physical activity

A useful concept is:

energy intake compared with energy expenditure

---

Energy Intake and Expenditure

If energy intake and expenditure are approximately balanced over time:

energy intake ≈ energy expenditure

body energy stores tend to remain relatively stable.

If energy intake consistently exceeds expenditure:

energy intake > energy expenditure

the excess can be stored, including as body fat.

If energy intake remains below expenditure:

energy intake < energy expenditure

the body must draw on stored energy.

Short-term changes are normal. Long-term patterns are what matter most.

---

What Determines Energy Needs?

Energy needs vary considerably between people.

Important factors include:

• age
• sex
• body size and composition
• activity level
• growth
• pregnancy
• breastfeeding
• health
• environment

Therefore, there is no single diet that is appropriate for every person.

---

Children and Adolescents

Children and adolescents require nutrients for both:

normal body function

and:

growth and development

 

 

 

7

Important considerations include adequate:

• energy
• protein
• calcium
• iron
• vitamins
• essential fats

Nutrient requirements change throughout childhood and adolescence.

---

Adults

Adults require energy and nutrients for:

• metabolism
• physical activity
• tissue maintenance and repair
• immune function
• normal organ function

Energy needs can differ greatly depending on lifestyle.

For example, an adult performing heavy physical work may require substantially more energy than someone of similar size who is less active.

---

Athletes and Highly Active People

People who exercise frequently may have increased requirements for:

• total energy
• carbohydrates
• protein
• fluids
• electrolytes

 

 

 

6

The exact needs depend on:

• sport
• training intensity
• training duration
• body size
• goals
• environmental conditions

An endurance athlete and a strength athlete may have different nutritional priorities.

---

Pregnancy

Pregnancy changes nutritional requirements because nutrients support both the pregnant person's body and fetal development.

Needs for several nutrients may increase, including certain:

• vitamins
• minerals
• protein
• energy

Specific recommendations vary by individual and stage of pregnancy, so medical or dietetic guidance is important for individualized planning.

---

Older Adults

Nutritional needs also change with age.

Some older adults may need to pay particular attention to:

• protein
• calcium
• vitamin D
• vitamin B12
• fibre
• hydration

Energy needs may decrease if physical activity decreases, while the need for essential nutrients remains.

This makes nutrient density especially important.

---

What Is Nutrient Density?

Nutrient density describes how much useful nutrition a food provides relative to its energy content.

A nutrient-dense food may provide substantial:

• vitamins
• minerals
• protein
• fibre
• essential fatty acids

without providing excessive energy.

Examples can include:

• vegetables
• fruits
• legumes
• whole grains
• fish
• eggs
• nuts and seeds

---

Evaluating a Diet

To decide whether a diet is balanced, simply counting calories is not enough.

Ask several questions.

Does it provide enough energy?

Does it provide adequate protein?

Are there varied fruits and vegetables?

Does it contain useful sources of fibre?

Does it provide essential fats?

Does it provide important vitamins and minerals?

Does it provide adequate fluids?

Are highly processed foods, added sugars, sodium, and saturated fats being consumed in reasonable amounts?

---

Example Diet A

Imagine someone eats:

Breakfast: sugary drink and pastry

Lunch: fries and soft drink

Snack: candy

Dinner: instant noodles

This diet may provide substantial energy.

However, it may be low in:

• fibre
• protein
• some vitamins
• some minerals
• fruit and vegetable variety

It may also contain high amounts of:

• added sugars
• sodium
• some types of fat

Therefore:

enough calories ≠ balanced nutrition

---

Example Diet B

Consider:

Breakfast: oatmeal, fruit and yoghurt

Lunch: rice, vegetables and grilled chicken or tofu

Snack: fruit and nuts

Dinner: fish or beans, vegetables and potatoes

Drinks: mainly water

 

 

 

5

This pattern provides greater variety across:

• carbohydrates
• protein
• fats
• fibre
• vitamins
• minerals

Individual portion sizes would still depend on the person's needs.

---

Comparing Two Breakfasts

Breakfast 1

• sweetened drink
• doughnut

Breakfast 2

• oatmeal
• banana
• yoghurt
• water

Both breakfasts provide energy.

However, Breakfast 2 is likely to provide a wider range of:

• fibre
• protein
• vitamins
• minerals

This demonstrates why food should be evaluated using more than calories alone.

---

Reading Food Labels

Nutrition labels can help evaluate foods.

 

 

 

5

Labels may provide information about:

• energy
• protein
• carbohydrate
• sugars
• fat
• saturated fat
• fibre
• sodium
• selected vitamins and minerals

Always check the:

serving size

or:

amount per 100 g

when comparing products.

---

Comparing Similar Foods

Suppose two breakfast cereals have similar energy values.

Cereal A contains:

• more fibre
• less added sugar
• less sodium

Cereal B contains:

• less fibre
• more added sugar
• more sodium

The energy values alone would not reveal these differences.

This demonstrates why evaluating overall nutritional composition is important.

---

Added Sugars

Some foods naturally contain sugars.

For example:

• fruit contains naturally occurring sugars
• milk contains lactose

Other foods contain sugars added during manufacturing or preparation.

Frequent high intake of foods and drinks containing substantial added sugars can make it easier to consume excess energy and is associated with dental and other health concerns.

The context of the whole diet matters.

---

Sodium

Sodium is an essential mineral.

It contributes to:

• nerve impulses
• muscle function
• fluid balance

However, excessive sodium intake can contribute to elevated blood pressure in susceptible people.

Many processed foods can contain substantial amounts of sodium.

Again:

essential nutrient ≠ unlimited intake

---

Saturated and Unsaturated Fats

A balanced diet should consider the types of dietary fats consumed.

Unsaturated fats are commonly found in:

• nuts
• seeds
• fish
• avocado
• vegetable oils

Saturated fats are found in varying amounts in:

• butter
• fatty meats
• some dairy products
• coconut and palm oils
• many processed foods

 

 

 

5

Dietary guidelines commonly recommend emphasizing unsaturated fats while limiting excessive saturated fat intake.

---

Variety Matters

Imagine eating the same food every day.

Even if that food contains several useful nutrients, it is unlikely to provide every nutrient in appropriate amounts.

Eating a variety of foods increases the likelihood of obtaining:

• different vitamins
• different minerals
• essential amino acids
• essential fatty acids
• fibre
• other useful compounds

Therefore:

variety is an important characteristic of a balanced diet.

---

Balance Happens Over Time

Not every individual meal needs to contain every nutrient in perfect proportions.

For example, one lunch may contain more carbohydrate.

Another meal may contain more protein.

One day may include more vegetables than another.

What matters most is the overall dietary pattern.

A useful principle is:

evaluate the diet over days and weeks, not one isolated meal.

---

Cultural Differences

Balanced diets can look very different around the world.

 

 

 

6

A balanced meal might contain:

rice + vegetables + tofu + fish

or:

whole-grain bread + lentils + salad + yoghurt

or:

beans + corn + vegetables + avocado

or many other combinations.

There is no single food that every person must eat to have a balanced diet.

Nutrient requirements can be met through many dietary patterns.

---

Vegetarian and Vegan Diets

A vegetarian or vegan diet can be nutritionally adequate when appropriately planned.

Plant-based protein sources include:

• beans
• lentils
• chickpeas
• tofu
• tempeh
• nuts
• seeds

 

 

 

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Depending on the dietary pattern, particular attention may be needed for nutrients such as:

• vitamin B12
• iron
• calcium
• vitamin D
• iodine
• omega-3 fatty acids
• protein

Vitamin B12 is particularly important in vegan diets because reliable dietary sources are generally fortified foods or supplements.

---

Allergies and Intolerances

Food allergies and intolerances can change how someone designs a balanced diet.

For example, a person avoiding dairy products may need alternative sources of:

• calcium
• protein
• vitamin D, depending on local fortification

Someone avoiding gluten must obtain carbohydrates, fibre and other nutrients from appropriate gluten-free foods.

Removing a food group requires thinking about:

what nutrients need to be replaced?

---

Designing a Balanced Daily Meal Plan

A meal plan should consider:

1. The individual

Age, activity and other nutritional needs.

2. Variety

Use different foods across the day.

3. Vegetables and fruits

Include them regularly.

4. Carbohydrate sources

Prefer nutrient-rich and higher-fibre options where practical.

5. Protein

Include appropriate protein-rich foods.

6. Healthy fats

Include suitable sources of unsaturated fats.

7. Water

Maintain adequate hydration.

8. Overall balance

Avoid consistently excessive amounts of added sugars, sodium and saturated fats.

---

Example Balanced Daily Plan

This is an example rather than a prescription for every person.

Breakfast

• oatmeal
• banana or berries
• yoghurt or fortified alternative
• water

Lunch

• brown rice or another grain
• chicken, tofu or beans
• mixed vegetables
• fruit
• water

Snack

• fruit
• nuts or yoghurt

Dinner

• fish, lentils or another protein source
• potatoes, rice or whole grains
• mixed vegetables
• water

 

 

 

5

The exact quantities should be adjusted for the individual.

---

Improving an Unbalanced Meal

Suppose lunch is:

fried potatoes + soft drink

How could we improve it?

Add:

a protein source

such as beans, eggs, fish, chicken or tofu.

Add:

vegetables

for fibre, vitamins and minerals.

Replace or reduce the sugary drink with:

water

Consider including:

fruit

The goal is not necessarily to eliminate every enjoyable food.

The goal is to improve the overall nutritional balance.

---

Designing for an Athlete

A highly active student may require more energy than a less active student.

A meal could include:

• rice or pasta for carbohydrate
• chicken, fish, beans or tofu for protein
• vegetables
• healthy fat
• fruit
• adequate fluids

Around prolonged exercise, carbohydrate and fluid needs may be particularly important.

After exercise, both energy and protein contribute to recovery.

---

Designing for Growth

A growing teenager requires nutrients to support:

• bone development
• muscle growth
• new cells
• blood production
• brain development
• hormonal processes

Important nutrients include:

• protein
• calcium
• iron
• vitamins
• essential fats
• sufficient energy

 

 

 

6

A diet that provides too little energy or too little variety may make it difficult to meet these needs.

---

Evaluating Dietary Claims

Advertisements may describe foods as:

"high protein"

"low fat"

"natural"

"high fibre"

"no added sugar"

One claim does not tell you whether the entire food or diet is nutritionally balanced.

For example:

high protein ≠ automatically healthy

and:

low fat ≠ automatically healthy

A better evaluation considers:

• serving size
• overall nutrient composition
• ingredients
• dietary context

---

Healthy Eating Is Not About One Food

Foods are eaten as part of an overall diet.

One dessert does not automatically make a diet unbalanced.

One salad does not automatically make a diet balanced.

The important pattern is:

what is eaten regularly over time

This is why nutritional evaluation should focus on overall dietary patterns rather than labeling individual foods simply as "good" or "bad."

---

From Food to Cells

A balanced diet ultimately supports cells.

Consider the pathway:

balanced diet

↓

digestion

↓

nutrient absorption

↓

transport in blood and lymph

↓

delivery to cells

↓

cellular processes

 

 

 

5

Cells then use these nutrients for:

• respiration
• growth
• repair
• protein synthesis
• membrane production
• cell division
• many other processes

---

Balanced Diets and Homeostasis

Nutrition also contributes to homeostasis — maintaining relatively stable internal conditions.

For example:

Water and electrolytes help maintain:

fluid balance

Glucose regulation helps maintain:

blood glucose concentration

Calcium regulation helps support:

nerve, muscle and bone functions

Adequate nutrition therefore contributes to the body's ability to maintain stable internal conditions.

---

Common Misconception: Balanced Means Equal Amounts

A balanced diet does not contain equal quantities of every nutrient.

The body needs nutrients in very different amounts.

For example, we need much more water than vitamin B12.

Balance means:

appropriate amounts and proportions

not:

equal amounts

---

Common Misconception: Healthy Diets Must Be Expensive

Balanced diets can be built from many relatively simple foods.

Examples include:

• oats
• rice
• beans
• lentils
• eggs
• seasonal vegetables
• frozen vegetables
• potatoes
• canned fish
• fruit

Planning and food choice can often matter more than buying expensive products marketed as "health foods."

---

Common Misconception: Supplements Replace Food

Vitamin and mineral supplements can be useful in specific circumstances.

However, supplements generally do not provide everything found in a varied diet, such as:

• protein
• fibre
• essential fats
• energy
• the full variety of food components

Supplements should therefore not automatically be considered substitutes for a balanced diet.

---

Common Misconception: Everyone Needs the Same Diet

Nutritional needs differ.

Consider:

Child

Needs nutrients for growth.

Teenager

May have high requirements during rapid development.

Athlete

May require additional energy and fluids.

Older adult

May have lower energy requirements while still requiring nutrient-dense foods.

Pregnant person

Has altered requirements for several nutrients.

Therefore:

balanced for one person may not be balanced for another.

---

A Simple Diet Evaluation Framework

When evaluating a diet, use:

V – Variety

Are many different nutrient-rich foods included?

E – Energy

Does the diet provide an appropriate amount of energy?

N – Nutrients

Are protein, vitamins, minerals, essential fats and other nutrients represented?

F – Fibre

Are whole grains, vegetables, fruits or legumes included?

W – Water

Is hydration adequate?

This provides a useful starting framework.

---

A Balanced Diet Challenge

Imagine you are planning meals for a student with a full day of school and sports practice.

Your plan should provide:

• sufficient energy
• carbohydrate
• protein
• vegetables
• fruit
• healthy fats
• fibre
• calcium-rich foods or alternatives
• iron-containing foods
• water

The challenge is not simply:

"How many calories?"

It is:

"How can we provide the energy AND nutrients this person needs?"

---

Did You Know?

Two meals can contain approximately the same amount of energy but have very different nutritional compositions.

 

 

 

5

For example, one meal might contain mostly refined carbohydrate and added fat.

Another might contain:

• whole grains
• vegetables
• protein
• healthy fats
• fibre
• vitamins
• minerals

This is why calories alone cannot tell us whether a diet is balanced.

---

Key Terms

• Balanced diet: Dietary pattern providing energy and essential nutrients in appropriate amounts and proportions.
• Macronutrient: Nutrient required in relatively large amounts.
• Micronutrient: Nutrient required in relatively small amounts.
• Carbohydrate: Major nutrient that can provide energy.
• Protein: Nutrient supplying amino acids for growth, repair and other functions.
• Lipid: Nutrient involved in energy storage, membranes and other functions.
• Vitamin: Organic micronutrient required for normal body processes.
• Mineral: Inorganic nutrient required for normal body functions.
• Fibre: Plant-derived dietary material that supports digestive health.
• Hydration: Maintaining adequate water in the body.
• Energy intake: Energy obtained from food and drink.
• Energy expenditure: Energy used by the body.
• Nutrient density: Nutrient content of a food relative to its energy content.
• Deficiency: Insufficient supply or availability of a required nutrient.
• Serving size: Defined amount of food used when presenting nutritional information.
• Whole grain: Grain containing the major original parts of the grain kernel.
• Saturated fat: Fat containing fatty acids without carbon-carbon double bonds.
• Unsaturated fat: Fat containing fatty acids with one or more carbon-carbon double bonds.
• Homeostasis: Maintenance of relatively stable internal conditions.

---

Key Relationships

Energy balance:

energy intake ↔ energy expenditure

Energy supply:

carbohydrates and lipids → metabolic fuel

Growth and repair:

protein → amino acids → new proteins

Bone health:

calcium + vitamin D + protein + other nutrients → healthy bone maintenance

Digestive health:

fibre + water → normal digestive function

Overall:

varied foods → balanced nutrient intake → digestion and absorption → cellular function

---

Key Takeaways

• A balanced diet provides energy and nutrients in appropriate amounts.
• A balanced diet includes carbohydrates, proteins, lipids, vitamins, minerals and water.
• Fibre is also an important component of healthy dietary patterns.
• Balanced does not mean equal amounts of every nutrient.
• Different nutrients are required in different quantities.
• Variety helps provide a wider range of nutrients.
• Vegetables and fruits provide fibre, vitamins, minerals and other useful compounds.
• Whole grains and other carbohydrate-rich foods can provide energy and fibre.
• Protein-rich foods supply amino acids needed for growth and repair.
• Dietary fats are needed for cell membranes, energy storage and absorption of fat-soluble vitamins.
• Unsaturated fats can be emphasized as part of a balanced dietary pattern.
• Adequate water is essential for transport, metabolism and temperature regulation.
• Energy intake should be considered in relation to energy expenditure over time.
• Nutritional needs vary between individuals.
• Age, body size, activity, growth, pregnancy and health can affect nutritional requirements.
• Children and adolescents need sufficient nutrients to support growth and development.
• Highly active people may require more energy, carbohydrate and fluids.
• Older adults may need fewer calories while still requiring nutrient-dense foods.
• Vegetarian and vegan diets can be nutritionally adequate when appropriately planned.
• Food allergies and intolerances may require alternative nutrient sources.
• A diet should be evaluated using more than its calorie content.
• Nutrition labels can help compare foods.
• Serving size must be considered when reading nutrition information.
• A single nutritional claim does not determine whether a food is nutritionally balanced.
• Nutrient density helps describe the nutritional value of foods relative to their energy content.
• Balance should be evaluated across the overall dietary pattern, not a single meal.
• Healthy dietary patterns can take many cultural forms.
• Supplements do not automatically replace the benefits of a varied diet.
• A useful meal-planning principle is variety + appropriate portions + nutrient-rich foods + adequate hydration.
• A balanced diet ultimately provides cells with the energy, raw materials, vitamins, minerals and water needed for growth, repair and normal body function.

 

 

 

3. Malnutrition and Deficiency Diseases

 

 

 

5

What Is Malnutrition?

Malnutrition occurs when a person's intake or use of energy and nutrients does not adequately meet the body's needs.

Malnutrition does not simply mean "not eating enough."

It can result from:

• too little food
• too much energy intake
• too little of a particular nutrient
• an unbalanced diet
• poor absorption of nutrients
• illness that changes nutrient requirements or losses

Therefore, someone can consume plenty of food and still experience a form of malnutrition.

The Main Forms of Malnutrition

Malnutrition can broadly involve:

Undernutrition

The body receives or absorbs insufficient energy or nutrients.

Micronutrient deficiencies

The body lacks sufficient amounts of particular vitamins or minerals.

Overnutrition

Energy or certain nutrients are consumed in excess relative to the body's needs over time.

These forms can sometimes occur together.

For example, a diet may provide excessive energy while still being deficient in particular vitamins or minerals.

Undernutrition

Undernutrition occurs when the body does not receive or effectively use enough energy, protein, or other nutrients to meet its requirements.

Possible causes include:

• inadequate food intake
• limited access to nutritious food
• illness
• digestive disorders
• poor nutrient absorption
• increased nutritional requirements
• prolonged infection
• highly restrictive diets

 

 

 

7

Effects of Undernutrition

The effects depend on:

• which nutrients are lacking
• severity
• duration
• age
• health
• individual nutritional requirements

Possible consequences include:

• weight loss
• reduced growth in children
• muscle loss
• fatigue
• reduced physical performance
• impaired immune function
• slower wound healing
• increased vulnerability to illness

Severe or prolonged undernutrition can be life-threatening.

Overnutrition

Overnutrition occurs when the body consistently receives more energy or particular nutrients than it requires.

For energy:

energy intake > energy expenditure over time

can lead to increased energy storage.

Much of this excess energy can eventually be stored as:

body fat

 

 

 

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Overnutrition is not simply about eating a large meal occasionally. Long-term dietary patterns are more important.

Health Consequences of Long-Term Overnutrition

Long-term excess energy intake can contribute to excess body fat.

Excess body fat is associated with increased risk of several conditions, including:

• type 2 diabetes
• cardiovascular disease
• high blood pressure
• some cancers
• joint problems
• fatty liver disease

Risk is influenced by many factors, including:

• diet
• physical activity
• genetics
• age
• sleep
• smoking
• environment
• existing health conditions

Diet is important, but it is not the only factor affecting long-term health.

Micronutrient Deficiency

A nutrient deficiency occurs when the body does not have enough of a particular nutrient to maintain normal function.

Micronutrient deficiencies commonly involve:

vitamins

or:

minerals

Examples include deficiencies of:

• iron
• vitamin A
• vitamin C
• vitamin D
• iodine

 

 

 

5

Why Do Deficiencies Occur?

A deficiency can occur for several reasons.

Insufficient intake

The diet does not contain enough of the nutrient.

Poor absorption

The nutrient is present in food but is not absorbed adequately.

Increased requirements

Growth, pregnancy, illness, or other circumstances can increase nutrient requirements.

Increased loss

Certain illnesses or other conditions can cause nutrients to be lost from the body.

Therefore:

nutrient deficiency does not always mean that someone simply chose the wrong foods.

Iron Deficiency

Iron is required for the production of:

haemoglobin

Haemoglobin is found in red blood cells and carries oxygen.

The relationship is:

iron → haemoglobin → oxygen transport

 

 

 

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If insufficient iron is available, the body may be unable to produce enough normal haemoglobin.

Iron-Deficiency Anaemia

One important consequence of iron deficiency is:

iron-deficiency anaemia

A person may experience symptoms such as:

• tiredness
• weakness
• shortness of breath
• reduced exercise tolerance
• difficulty concentrating

These symptoms occur because the blood's ability to transport oxygen can be reduced.

Sources of Iron

Iron-containing foods include:

• meat
• fish
• beans
• lentils
• leafy green vegetables
• fortified cereals
• some seeds and nuts

Vitamin C can improve the absorption of non-haem iron, the form commonly found in plant foods.

For example:

lentils + vitamin C-rich vegetables

can be a useful dietary combination.

Preventing Iron Deficiency

Strategies can include:

• consuming appropriate iron-rich foods
• eating a varied diet
• including vitamin C-rich foods alongside plant sources of iron
• using appropriately fortified foods where available
• addressing medical causes of blood loss or poor absorption

Iron supplements may be recommended in some circumstances, but unnecessary high-dose supplementation can be harmful.

Vitamin C Deficiency

Vitamin C is important for several functions, including:

• collagen formation
• wound healing
• antioxidant activity
• supporting iron absorption

Severe, prolonged vitamin C deficiency can cause:

scurvy

 

 

 

5

Scurvy

Collagen is an important structural protein.

When vitamin C deficiency interferes with normal collagen production, tissues can become weakened.

Symptoms of scurvy can include:

• bleeding gums
• easy bruising
• poor wound healing
• fatigue
• weakness

Severe cases can cause serious complications.

Preventing Vitamin C Deficiency

Vitamin C is found in many fruits and vegetables.

Sources include:

• oranges and other citrus fruits
• peppers
• strawberries
• broccoli
• tomatoes
• kiwi fruit

A varied diet containing fruits and vegetables generally helps provide adequate vitamin C.

Vitamin D Deficiency

Vitamin D is important for maintaining appropriate calcium and phosphate levels.

It contributes to:

normal bone mineralization

The body can produce vitamin D in the skin when exposed to sufficient ultraviolet B radiation.

Vitamin D can also be obtained from:

• certain fish
• egg yolks
• fortified foods
• supplements when appropriate

 

 

 

7

Rickets

Severe vitamin D deficiency in growing children can contribute to:

rickets

Rickets involves inadequate mineralization of growing bones.

Possible effects include:

• soft or weak bones
• skeletal deformities
• impaired growth
• bone pain
• muscle weakness

Vitamin D, calcium, and phosphate are closely connected to normal bone development.

Vitamin D Deficiency in Adults

In adults, severe vitamin D deficiency can cause:

osteomalacia

This involves poor mineralization of bone.

It can contribute to:

• bone pain
• muscle weakness
• increased risk of fractures

This is different from osteoporosis, although both can affect bone health.

Preventing Vitamin D Deficiency

Prevention may involve:

• appropriate dietary sources
• fortified foods
• suitable sunlight exposure
• supplementation when medically appropriate

The best approach varies according to:

• age
• skin pigmentation
• location
• season
• lifestyle
• health
• individual risk

Vitamin A Deficiency

Vitamin A is important for:

• vision
• immune function
• growth
• maintenance of epithelial tissues

Severe vitamin A deficiency can affect vision.

One early problem can be:

night blindness

 

 

 

5

More severe deficiency can damage the eye and potentially lead to blindness.

Sources of Vitamin A

Vitamin A or its precursors can be obtained from foods such as:

• liver
• eggs
• dairy products
• carrots
• sweet potatoes
• pumpkin
• dark green leafy vegetables

Orange and dark green vegetables often contain:

beta-carotene

which the body can convert into vitamin A.

Iodine Deficiency

Iodine is required to make:

thyroid hormones

These hormones contribute to the regulation of:

• metabolism
• growth
• development

Insufficient iodine can interfere with thyroid function.

 

 

 

5

Goitre

One possible consequence of iodine deficiency is enlargement of the thyroid gland.

This is called:

goitre

The thyroid is located in the neck.

However, goitre can have causes other than iodine deficiency, so the presence of an enlarged thyroid does not by itself identify the cause.

Why Iodine Is Especially Important During Development

Thyroid hormones are particularly important during fetal and early childhood development.

Severe iodine deficiency during pregnancy can interfere with normal brain and nervous-system development.

This demonstrates an important idea:

the same nutrient deficiency can have different consequences at different stages of life.

Preventing Iodine Deficiency

One important public-health strategy is:

iodized salt

Iodized salt contains added iodine.

Other dietary sources may include:

• seafood
• dairy products
• eggs
• some seaweeds

The iodine content of foods varies depending on environmental and agricultural conditions.

Calcium Deficiency and Bone Health

Calcium is important for:

• bones
• teeth
• muscle contraction
• nerve signaling
• blood clotting

Long-term inadequate calcium intake can contribute to poor bone health.

However, bone health depends on more than calcium alone.

Important factors also include:

• vitamin D
• protein
• physical activity
• hormones
• age
• genetics

 

 

 

6

Protein-Energy Undernutrition

Severe undernutrition can involve inadequate:

energy

and:

protein

Growing children are particularly vulnerable because they require nutrients for both:

maintenance + growth

Severe protein-energy undernutrition can interfere with:

• growth
• muscle development
• immune function
• organ function
• recovery from illness

Marasmus

Marasmus is a severe form of undernutrition associated with major energy deficiency.

It can involve:

• severe wasting
• loss of muscle and body fat
• poor growth
• weakness

The body lacks sufficient energy to maintain normal growth and tissue stores.

Kwashiorkor

Kwashiorkor is a severe form of malnutrition classically associated with severe dietary inadequacy and characterized by features that can include:

• oedema
• changes in skin and hair
• impaired growth
• enlarged fatty liver

Its biology is complex and cannot be explained simply as "protein deficiency alone."

This is an important example of why real nutritional diseases can be more complicated than simplified textbook descriptions.

Deficiency Disease Summary

A Deficiency Is Not Always Obvious

Someone can consume enough calories but still lack particular nutrients.

Consider a diet containing large amounts of:

• refined grains
• sugary drinks
• highly processed snack foods

but very little:

• fruit
• vegetables
• protein-rich foods
• varied nutrient sources

The person may consume sufficient or excessive energy while still having inadequate intake of some micronutrients.

This is sometimes described as the:

double burden of malnutrition

The Double Burden of Malnutrition

A population, household, or even an individual can experience different forms of malnutrition simultaneously.

For example:

excess energy intake

may coexist with:

iron deficiency

or another micronutrient deficiency.

 

 

 

4

This demonstrates why body size alone does not tell us whether someone's nutritional intake is adequate.

Malabsorption

Sometimes the problem is not the amount of nutrient in the diet.

The digestive system may not absorb the nutrient effectively.

This is called:

malabsorption

Conditions affecting the intestine can interfere with absorption of:

• iron
• vitamins
• fats
• carbohydrates
• other nutrients

Therefore:

adequate intake does not always guarantee adequate absorption.

Nutrition and the Digestive System

The pathway from food to body cells involves several stages:

food

↓

digestion

↓

absorption

↓

transport

↓

cellular use

A problem at any stage can affect nutritional status.

For example:

nutrient present in food + poor absorption = possible deficiency

Diet and Long-Term Health

Dietary patterns can influence health over many years.

Long-term patterns associated with better health generally include appropriate amounts and variety of:

• vegetables
• fruits
• whole grains
• legumes
• nuts and seeds
• protein-rich foods
• unsaturated fats

while limiting consistently excessive intake of:

• added sugars
• sodium
• saturated fats
• highly processed foods that displace nutrient-rich foods

 

 

 

6

Diet and Cardiovascular Health

Cardiovascular disease affects the heart and blood vessels.

Long-term cardiovascular risk can be influenced by factors including:

• blood pressure
• blood cholesterol
• smoking
• diabetes
• physical activity
• body composition
• genetics
• diet

Dietary patterns containing plenty of fibre-rich plant foods and appropriate types of dietary fat can contribute to cardiovascular health.

Diet and Type 2 Diabetes

Type 2 diabetes involves problems with the regulation of blood glucose.

Risk is influenced by multiple factors, including:

• genetics
• age
• body composition
• physical activity
• dietary patterns

Long-term excessive energy intake can contribute to excess body fat, which is an important risk factor for type 2 diabetes.

However:

diet is one risk factor among several

and should not be treated as the sole cause.

Diet and Blood Pressure

Blood pressure is influenced by:

• genetics
• age
• physical activity
• body composition
• diet
• sodium intake
• potassium intake
• alcohol intake
• other health factors

Consistently high sodium intake can contribute to elevated blood pressure, particularly in salt-sensitive individuals.

This is one reason many dietary guidelines recommend limiting excessive sodium intake.

Diet and Bone Health

Bone health depends on long-term nutrition and lifestyle.

Important factors include:

• calcium
• vitamin D
• protein
• physical activity
• hormones
• age
• genetics

Weight-bearing physical activity also helps stimulate bone maintenance.

Therefore:

healthy bones require both nutrition and appropriate physical activity.

Poor Nutrition Can Affect Learning and Performance

Nutrition can influence more than physical growth.

Inadequate nutrition can affect:

• concentration
• energy levels
• physical performance
• recovery
• immune function

For students, adequate nutrition and hydration can therefore support participation in both:

learning

and:

physical activity

Preventing Nutrient Deficiencies

A major strategy is eating a varied, balanced diet.

This can include:

• vegetables
• fruits
• whole grains
• legumes
• protein-rich foods
• appropriate fat sources
• adequate fluids

 

 

 

6

Different foods supply different nutrients.

Therefore:

dietary variety reduces the risk of missing particular nutrients.

Food Fortification

Food fortification involves adding nutrients to foods.

Examples can include:

• iodine added to salt
• vitamin D added to some foods
• iron added to cereals or flour
• folic acid added to some grain products

Fortification can help increase nutrient intake across large populations.

Supplementation

A dietary supplement provides concentrated amounts of particular nutrients.

Examples include:

• iron
• vitamin D
• vitamin B12
• folic acid

Supplements can be useful when:

• dietary intake is insufficient
• requirements are increased
• absorption is limited
• a deficiency has been diagnosed
• specific public-health guidance recommends them

However:

more is not always better.

Some nutrients can be harmful in excessive amounts.

Prevention Through Public Health

Preventing malnutrition is not only an individual responsibility.

Public-health approaches can include:

• access to nutritious foods
• clean water
• sanitation
• nutrition education
• food fortification
• maternal and infant nutrition programs
• school meal programs
• disease prevention
• healthcare access

Malnutrition therefore involves both:

biology

and:

social and environmental conditions.

Evaluating a Diet for Deficiency Risk

Consider this daily pattern:

Breakfast: sweetened drink

Lunch: white bread and chips

Snack: candy

Dinner: instant noodles

Possible concerns include low intake of:

• fibre
• protein
• iron
• calcium
• some vitamins
• vegetables and fruits

The diet may still provide considerable energy.

This illustrates:

high energy intake does not guarantee adequate nutrition.

Improving the Diet

A more varied pattern could include:

Breakfast: oatmeal + fruit + yoghurt

Lunch: rice + vegetables + beans, tofu, fish, eggs, or chicken

Snack: fruit + nuts

Dinner: whole grains or potatoes + vegetables + protein source

Drinks: mainly water

 

 

 

7

The goal is to increase:

variety + nutrient density + appropriate balance

rather than simply increasing the amount of food.

Case Study: Fatigue

A student frequently feels tired.

Their diet contains very little iron-rich food.

One possible nutritional explanation could be:

insufficient iron

↓

reduced haemoglobin production

↓

reduced oxygen-carrying capacity

↓

fatigue

However, fatigue has many possible causes.

A symptom alone cannot diagnose a nutrient deficiency.

Case Study: Bone Development

A growing child has very low vitamin D availability.

Possible pathway:

low vitamin D

↓

impaired calcium/phosphate regulation

↓

poor bone mineralization

↓

increased risk of rickets

This demonstrates how a micronutrient can influence an entire organ system.

Case Study: A High-Energy but Low-Quality Diet

A person regularly consumes enough energy but eats very little:

• fruit
• vegetables
• whole grains
• legumes
• varied protein sources

This person is not necessarily undernourished in terms of energy.

However, they could still have inadequate intake of particular:

vitamins, minerals, fibre, or other nutrients.

This is why malnutrition cannot be judged simply by how much someone eats.

Diet Is About Patterns

Eating one highly nutritious meal does not guarantee long-term health.

Eating one less nutritious meal does not create a deficiency disease.

Nutritional health reflects patterns developing over:

days → weeks → months → years

This is especially important when evaluating the relationship between diet and chronic disease.

Risk Is Not Certainty

Suppose a particular dietary pattern is associated with increased risk of a disease.

This does not mean:

diet → guaranteed disease

Instead:

diet + genetics + activity + environment + age + other factors → overall risk

Nutrition often changes the probability of health outcomes rather than determining them completely.

This distinction is essential when interpreting health information.

Evaluating Nutrition Claims

Imagine an advertisement says:

"This drink contains 100% of your daily vitamin C, so it keeps you healthy."

A scientific evaluation should ask:

• What else does the drink contain?
• How much sugar does it contain?
• What is the serving size?
• What other nutrients does it provide?
• What does the person's overall diet look like?
• Does the evidence support the health claim?

One nutrient does not determine the nutritional quality of an entire diet.

Common Misconception: Malnutrition Means Starvation

Starvation is an extreme form of inadequate energy intake.

Malnutrition is a much broader concept.

It can include:

undernutrition

micronutrient deficiency

and:

overnutrition

A person does not need to be starving to be malnourished.

Common Misconception: Someone Who Eats a Lot Cannot Be Malnourished

A person can consume excessive energy while receiving insufficient amounts of particular nutrients.

For example:

high energy + low iron intake

could still contribute to iron deficiency.

Nutritional status depends on:

quality + quantity + absorption + individual needs

Common Misconception: Deficiency Diseases Develop Immediately

Most deficiency diseases develop after inadequate nutrient availability persists.

The body may store some nutrients.

For example, certain vitamins and minerals can be stored to varying degrees.

Therefore, symptoms may appear only after stores become depleted or physiological functions are affected.

Common Misconception: Supplements Prevent Every Deficiency

Supplements can be useful in appropriate circumstances.

However, they cannot automatically compensate for every problem associated with an unbalanced diet.

Foods provide combinations of:

• nutrients
• fibre
• energy
• protein
• fats
• carbohydrates
• other food components

A supplement usually provides only selected substances.

Connecting Malnutrition to Homeostasis

The body attempts to maintain stable internal conditions.

Malnutrition can interfere with this.

For example:

iron deficiency → impaired oxygen transport

water deficiency → impaired fluid balance

iodine deficiency → altered thyroid function

vitamin D deficiency → impaired bone mineralization

energy deficiency → use of body energy stores

Nutrition is therefore closely connected to:

homeostasis

Connecting Malnutrition to Growth

Growing organisms require both:

energy

and:

raw materials

for new tissues.

A child experiencing prolonged undernutrition may have insufficient resources for normal growth.

This can affect:

• height
• muscle development
• bone development
• immune function
• organ development

Good nutrition is therefore particularly important during periods of rapid growth.

Did You Know?

Nutrient deficiencies can sometimes occur even when food appears plentiful.

 

 

 

5

This is sometimes called hidden hunger.

A person's diet may provide enough calories but insufficient amounts of important micronutrients such as:

• iron
• iodine
• vitamin A
• zinc

The problem may therefore be difficult to recognize simply by looking at how much food is available.

Major Deficiency Relationships

Iron deficiency

↓

less normal haemoglobin production

↓

reduced oxygen transport

↓

iron-deficiency anaemia

Vitamin C deficiency

↓

impaired collagen formation

↓

weakened connective tissues

↓

scurvy

Vitamin D deficiency

↓

impaired calcium and phosphate regulation

↓

poor bone mineralization

↓

rickets in children / osteomalacia in adults

Vitamin A deficiency

↓

impaired visual and epithelial function

↓

night blindness and potentially eye damage

Iodine deficiency

↓

reduced thyroid hormone production

↓

altered thyroid function

↓

goitre may develop

Deficiency Disease Summary

Key Terms

• Malnutrition: Inadequate, excessive, or imbalanced intake or utilization of energy and nutrients.
• Undernutrition: Insufficient energy or nutrients to meet the body's requirements.
• Overnutrition: Excess intake of energy or nutrients relative to requirements.
• Nutrient deficiency: Inadequate availability of a particular nutrient.
• Deficiency disease: Disease or disorder resulting from inadequate availability of a nutrient.
• Micronutrient: Vitamin or mineral required in relatively small amounts.
• Anaemia: Condition involving insufficient healthy red blood cells or haemoglobin; it has multiple possible causes.
• Iron-deficiency anaemia: Anaemia caused by insufficient available iron.
• Scurvy: Disease caused by severe vitamin C deficiency.
• Rickets: Disorder of bone mineralization in growing children, often associated with severe vitamin D deficiency.
• Osteomalacia: Poor mineralization of adult bone.
• Goitre: Enlargement of the thyroid gland.
• Malabsorption: Inadequate absorption of nutrients from the digestive system.
• Fortification: Addition of nutrients to foods.
• Supplementation: Use of concentrated nutrient preparations to increase intake.
• Nutrient density: Amount of useful nutrients provided relative to energy content.
• Hidden hunger: Micronutrient deficiency despite apparently adequate energy intake.
• Energy balance: Relationship between energy intake and energy expenditure.
• Chronic disease: Health condition that develops or persists over a long period.
• Homeostasis: Maintenance of relatively stable internal conditions.

Key Takeaways

• Malnutrition occurs when energy or nutrient intake or utilization does not adequately match the body's needs.
• Malnutrition does not simply mean starvation.
• Malnutrition includes undernutrition, micronutrient deficiencies, and overnutrition.
• A person can consume enough or excessive energy while still lacking important micronutrients.
• Undernutrition can result from inadequate food intake, disease, poor absorption, or increased requirements.
• Prolonged undernutrition can impair growth, immunity, physical performance, and tissue repair.
• Overnutrition can occur when energy intake consistently exceeds energy expenditure.
• Long-term excessive energy intake can contribute to excess body fat.
• Excess body fat is associated with increased risk of several chronic diseases.
• Iron is required for haemoglobin and oxygen transport.
• Iron deficiency can cause iron-deficiency anaemia.
• Vitamin C is important for collagen formation.
• Severe vitamin C deficiency causes scurvy.
• Vitamin D contributes to calcium regulation and normal bone mineralization.
• Severe vitamin D deficiency can contribute to rickets in children and osteomalacia in adults.
• Vitamin A is important for vision and tissue health.
• Severe vitamin A deficiency can cause night blindness and more serious eye damage.
• Iodine is required for thyroid hormone production.
• Iodine deficiency can interfere with thyroid function and may cause goitre.
• Severe energy and nutrient deficiency can lead to serious forms of undernutrition.
• Nutrient deficiencies may result from inadequate intake, poor absorption, increased requirements, or increased losses.
• A varied and balanced diet helps prevent many nutritional deficiencies.
• Food fortification can help prevent deficiencies across populations.
• Supplements can be useful in specific situations but should not automatically replace a balanced diet.
• Nutritional needs differ with age, growth, activity, pregnancy, illness, and other factors.
• Diet can influence long-term health, but it is one factor among genetics, physical activity, environment, and other influences.
• Associations between diet and disease represent changes in risk, not guarantees that a particular person will develop a disease.
• Nutritional status cannot be determined simply from body size or the amount of food someone eats.
• "Hidden hunger" describes micronutrient deficiencies that can occur even when energy intake appears adequate.
• Long-term health depends on dietary patterns developing over months and years rather than a single meal.
• A useful way to think about nutritional health is: enough energy + enough essential nutrients + appropriate balance + effective absorption = better support for normal growth, function, and long-term health.

4. Reading Food Labels

 

 

 

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Why Do Foods Have Labels?

Food labels provide information about what a food contains.

They can help consumers understand:

• serving size
• energy content
• carbohydrates
• sugars
• protein
• fats
• sodium
• fibre
• vitamins and minerals
• ingredients
• allergens

Labels allow us to compare foods using evidence rather than advertising or appearance.

A brightly coloured package may make a food look healthy, but the nutritional information provides much more useful evidence.

---

Different Countries, Different Labels

Food-label formats vary between countries.

Depending on where a product is sold, energy might be listed as:

Calories (kcal)

or:

kilojoules (kJ)

Nutrients might be reported:

per serving

per 100 g

per 100 mL

or a combination of these.

The basic skill remains the same:

identify the quantity → check the amount of food it represents → interpret the nutrients

---

The Nutrition Information Panel

A nutrition information panel summarizes the quantities of important nutrients in a food.

 

 

 

5

A typical label may contain information about:

• energy
• total fat
• saturated fat
• carbohydrate
• sugars
• fibre
• protein
• sodium

Some labels also list particular vitamins and minerals.

---

Step 1: Check the Serving Size

One of the most important pieces of information is:

serving size

A serving size tells you the quantity of food used to calculate the nutrition information.

For example:

Serving size: 30 g

Servings per package: 4

The nutritional values listed "per serving" apply to only:

30 g

not necessarily the entire package.

---

Serving Size Is Not Always Portion Size

A serving size is the amount used on the label.

A portion is the amount a person actually eats.

These may be different.

Suppose:

Serving size = 30 g

You eat = 60 g

You have eaten:

60 ÷ 30 = 2 servings

Therefore, the nutrient values per serving must be multiplied by 2.

---

Example: The Serving-Size Trap

Imagine a snack label says:

Serving size: 25 g

Calories per serving: 120 kcal

The packet contains 75 g.

Number of servings:

75 ÷ 25 = 3 servings

If the entire packet is eaten:

120 × 3 = 360 kcal

The package does not contain only 120 kcal.

It contains:

360 kcal

if the entire package is consumed.

This is why serving size should usually be one of the first things you check.

---

Energy

Food provides chemical energy.

Labels commonly express energy in:

kilocalories (kcal)

and/or:

kilojoules (kJ)

Although food packaging often uses the word Calories, a food Calorie is actually a kilocalorie.

Therefore:

1 Calorie = 1 kcal

and approximately:

1 kcal = 4.184 kJ

---

Where Does Food Energy Come From?

Most dietary energy comes from:

• carbohydrates
• fats
• proteins

Alcohol also provides energy, although it is not an essential nutrient.

Approximate energy values are:

Carbohydrate:

4 kcal per gram

Protein:

4 kcal per gram

Fat:

9 kcal per gram

This helps explain why foods containing large amounts of fat can be relatively energy-dense.

---

Calories Do Not Tell the Whole Story

Imagine two foods both provide:

200 kcal

They do not necessarily have the same nutritional value.

Food A might provide:

• protein
• fibre
• vitamins
• minerals

Food B might provide:

• large amounts of added sugar
• little fibre
• little protein

Therefore:

same calories ≠ same nutrition

 

 

 

5

---

Total Fat

The label may list:

Total Fat

This represents the total amount of dietary fat in the stated quantity of food.

Fat is an important nutrient.

The body uses fats for:

• energy storage
• cell membranes
• insulation
• absorption of fat-soluble vitamins
• production of signaling molecules

Therefore:

fat itself is not automatically unhealthy.

The amount and type of fat matter.

---

Saturated Fat

Labels often list:

Saturated Fat

separately from total fat.

For example:

Total fat: 12 g

Saturated fat: 4 g

This means that 4 g of the 12 g of fat is saturated fat.

The remaining fat includes other types.

Dietary guidelines generally recommend limiting excessive saturated-fat intake and replacing some saturated fats with unsaturated fats.

---

Unsaturated Fats

Foods containing unsaturated fats include:

• nuts
• seeds
• avocado
• fish
• olive oil
• many vegetable oils

 

 

 

5

Some labels list unsaturated fats separately, while others do not.

---

Carbohydrates

Labels commonly provide a value for:

Total Carbohydrate

Carbohydrates include several types of molecules.

Depending on the labeling system, the carbohydrate information may include or be accompanied by values for:

• sugars
• fibre
• starches

Carbohydrates can provide an important source of energy.

---

Total Sugars

A label may list:

Total Sugars

This tells you how much sugar is present in the food.

However, total sugar can include both:

naturally occurring sugars

and:

added sugars

For example, plain milk naturally contains the sugar:

lactose

Fruit naturally contains sugars such as:

fructose

So seeing "sugars" on a label does not automatically mean sugar was added during manufacturing.

---

Added Sugars

Some labeling systems separately list:

Added Sugars

These are sugars added during processing or preparation.

Examples include:

• sucrose
• glucose syrup
• corn syrup
• honey
• various syrups

 

 

 

6

This distinction can be useful when comparing products.

---

Fibre

Dietary fibre is the portion of plant-derived foods that is not completely digested by human digestive enzymes.

Fibre contributes to:

• normal bowel function
• digestive health
• feelings of fullness
• healthy dietary patterns

Sources include:

• whole grains
• vegetables
• fruits
• beans
• lentils
• nuts
• seeds

When comparing similar foods, fibre can be a useful factor to consider.

---

Protein

Labels commonly list:

Protein

Protein provides amino acids needed for:

• growth
• tissue repair
• enzymes
• antibodies
• transport proteins
• many cellular structures

 

 

 

4

A high-protein food is not automatically a balanced food, however.

The rest of the nutritional information still matters.

---

Sodium

Food labels commonly provide the amount of:

sodium

usually in:

milligrams (mg)

Sodium is an essential mineral involved in:

• nerve impulses
• muscle function
• fluid balance

However, consistently excessive sodium intake can contribute to elevated blood pressure in susceptible people.

Processed foods can be significant sources of sodium.

---

Sodium Is Not Exactly the Same as Salt

Table salt is primarily:

sodium chloride (NaCl)

The label may report sodium, not the total mass of salt.

Therefore:

500 mg sodium does not mean 500 mg of salt

This distinction is important when interpreting food labels.

---

Vitamins and Minerals

Some labels provide information about micronutrients such as:

• calcium
• iron
• potassium
• vitamin D
• vitamin C

 

 

 

These values can be especially useful when comparing foods intended to provide particular nutrients.

---

Percent Daily Value

Some labels include:

% Daily Value

often written:

%DV

This estimates how much a serving contributes toward a reference daily amount.

For example:

Iron: 20% DV

means one serving provides approximately:

20% of the reference Daily Value for iron

It does not necessarily mean every individual requires exactly that amount.

Individual nutritional needs vary.

---

Using % Daily Value

Suppose a food provides:

Fibre: 25% DV

This suggests that one serving makes a relatively substantial contribution toward the reference daily fibre amount.

Suppose another provides:

Fibre: 2% DV

It makes a much smaller contribution.

Therefore, %DV can make it easier to compare foods without remembering exact recommended amounts.

---

Per Serving vs Per 100 g

Labels may provide values:

per serving

or:

per 100 g

Per-serving information helps answer:

"What am I consuming in this portion?"

Per-100-g information is especially useful for answering:

"How do these two foods compare?"

---

Why Per 100 g Is Useful

Imagine two cereals.

Cereal A serving size:

30 g

Cereal B serving size:

45 g

Comparing their "per serving" values can be misleading because the serving sizes are different.

Instead, compare:

100 g of Cereal A

with:

100 g of Cereal B

Now the comparison uses the same amount.

---

Example Food Comparison

Consider two imaginary breakfast cereals.

Nutrient per 100 g	Cereal A	Cereal B
Energy	370 kcal	390 kcal
Sugar	8 g	24 g
Fibre	11 g	3 g
Protein	10 g	7 g
Sodium	210 mg	430 mg

What can we conclude?

Cereal A has:

• less sugar
• more fibre
• more protein
• less sodium
• slightly less energy

For someone prioritizing those nutritional characteristics, Cereal A may better fit those goals.

The important point is that the conclusion comes from:

nutritional evidence

rather than:

package design or advertising

---

Comparing Foods Fairly

When comparing two foods, use the same basis.

Good:

Food A per 100 g vs Food B per 100 g

or:

Food A per 100 mL vs Food B per 100 mL

Less useful:

Food A per serving vs Food B per serving

when the serving sizes are very different.

---

Reading the Ingredients List

The nutrition panel tells us how much of various nutrients a food contains.

The ingredients list tells us what was used to make the food.

 

 

 

6

Ingredients are commonly listed in descending order by weight.

This means:

first ingredient = present in the greatest amount by weight at the time of manufacture

The ingredients near the end are generally present in smaller amounts.

---

Example Ingredients List

Suppose a cereal lists:

Whole oats, sugar, wheat flour, vegetable oil, salt

The first ingredient is:

whole oats

so oats make up the largest ingredient by weight.

Now consider:

Sugar, wheat flour, corn syrup, oats, salt

Here:

sugar

is the largest ingredient by weight.

The two products may therefore have very different nutritional characteristics.

---

Sugar Can Have Many Names

Added sugars can appear under different names in ingredient lists.

Examples include:

• sugar
• sucrose
• glucose
• fructose
• maltose
• corn syrup
• glucose syrup
• rice syrup
• honey

Therefore, understanding the ingredients list can provide useful context alongside the nutrition panel.

---

Food Allergens

Food labels can also provide critical information about:

allergens

Common food allergens include:

• peanuts
• tree nuts
• milk
• eggs
• fish
• shellfish
• wheat
• soy
• sesame

 

 

 

4

Exact labeling requirements differ between countries.

For someone with a serious food allergy, allergen information can be essential for safety.

---

"Contains" Statements

A product might state:

Contains: milk, soy

This helps consumers identify allergens quickly.

Some products also include precautionary statements such as:

May contain peanuts

or:

Made in a facility that also processes nuts

These warnings can be important for people with allergies.

---

Nutrition Claims

Food packaging often contains claims such as:

• "high protein"
• "low fat"
• "reduced sugar"
• "whole grain"
• "source of fibre"
• "no added sugar"

These claims can provide information, but they do not tell the complete nutritional story.

A product advertised as:

low fat

could still contain substantial:

sugar or sodium

A product advertised as:

high protein

could still be high in:

sodium or saturated fat

Always examine the full label.

---

"No Added Sugar" Does Not Mean "No Sugar"

A product can contain naturally occurring sugars without having sugar added during processing.

For example:

100% fruit juice may contain substantial sugar even if the label says:

no added sugar

The claim means:

no additional sugar was added

not:

the product contains zero sugar

---

"Reduced" Does Not Mean "Low"

Suppose a regular product contains:

20 g sugar.

A "reduced sugar" version contains:

15 g.

The new product contains less sugar than the original.

But whether 15 g is a low amount is a different question.

Therefore:

reduced ≠ necessarily low

---

"Natural" Does Not Automatically Mean Nutritious

Words such as:

natural

premium

wholesome

traditional

may influence how consumers perceive a product.

But these words alone do not tell us:

• sugar content
• sodium content
• fibre content
• protein content
• saturated fat content
• energy content

The nutrition information provides stronger evidence.

---

Front-of-Pack Information

Some countries use front-of-package labeling systems to summarize nutritional information.

 

 

 

5

These systems may highlight:

• energy
• sugars
• fat
• saturated fat
• sodium or salt

Some use:

• colours
• letters
• symbols
• percentages
• rating systems

These can provide a quick summary, but the full nutrition panel contains more detail.

---

Evaluating a Food Product

A useful approach is to ask several questions.

1. How much am I actually eating?

Check:

serving size

2. How much energy does it provide?

Check:

Calories or kilojoules

3. What nutrients does it provide?

Check:

• protein
• fibre
• vitamins
• minerals

4. What might I want to limit?

Depending on the person's needs, consider:

• excessive added sugars
• excessive sodium
• excessive saturated fat

5. What are the main ingredients?

Read:

ingredients list

6. How does it fit into my overall diet?

A food should be evaluated as part of an overall dietary pattern.

---

A Simple Label-Reading Strategy

Remember:

S – Serving

Check the serving size.

E – Energy

Check Calories or kilojoules.

N – Nutrients

Look at protein, fibre, vitamins and minerals.

S – Sugar

Check total and added sugars where available.

F – Fat

Look at total and saturated fat.

S – Sodium

Check sodium.

This gives:

S-E-N-S-F-S

The exact order is less important than developing the habit of checking the whole label.

---

Worked Example

Suppose a snack has:

Serving size: 40 g

Energy: 180 kcal

Protein: 4 g

Fat: 7 g

Saturated fat: 2 g

Carbohydrate: 26 g

Sugars: 10 g

Fibre: 3 g

Sodium: 220 mg

The package contains:

80 g

If you eat the entire package, you consume two servings.

Therefore:

Energy:

180 × 2 = 360 kcal

Protein:

4 × 2 = 8 g

Fat:

7 × 2 = 14 g

Sugar:

10 × 2 = 20 g

Fibre:

3 × 2 = 6 g

Sodium:

220 × 2 = 440 mg

This demonstrates why serving size affects every value on the label.

---

Comparing Two Yoghurts

Suppose two yoghurts contain the following per 100 g.

Yoghurt A

Energy: 75 kcal

Protein: 5 g

Sugar: 6 g

Fat: 2 g

Yoghurt B

Energy: 105 kcal

Protein: 4 g

Sugar: 15 g

Fat: 3 g

If the goal is to choose the product with less sugar, the label provides clear evidence:

6 g vs 15 g

Yoghurt A contains:

15 − 6 = 9 g less sugar per 100 g

But another person may be comparing foods for a different reason.

This is why the "best" product depends partly on:

nutritional needs + dietary context

---

Comparing Two Drinks

Imagine:

Drink A

Serving: 250 mL

Sugar: 4 g

Drink B

Serving: 330 mL

Sugar: 5 g

At first glance:

Drink A = 4 g

Drink B = 5 g

But the serving sizes are different.

Calculate sugar per 100 mL.

Drink A:

4 ÷ 250 × 100 = 1.6 g per 100 mL

Drink B:

5 ÷ 330 × 100 ≈ 1.5 g per 100 mL

When equal volumes are compared, the drinks are much more similar than the original serving values suggested.

---

Labels and Mathematics

Reading food labels requires several mathematical skills.

You may need to:

• multiply
• divide
• calculate percentages
• compare ratios
• convert units
• calculate values for multiple servings

For example:

If 30 g contains 8 g sugar, then 60 g contains:

8 × 2 = 16 g sugar

If 100 g contains 12 g protein, then 50 g contains:

12 × 0.5 = 6 g protein

Food labels are therefore a practical application of mathematics.

---

Calculating the Percentage of a Food That Is Sugar

Suppose a 50 g snack contains:

10 g sugar

Percentage sugar by mass:

10 ÷ 50 × 100

= 20%

Therefore, sugar makes up:

20% of the snack's mass

This can help students connect nutrition labels with percentage calculations.

---

Evaluating the Whole Food

Suppose Food A is:

• low in sugar
• high in sodium
• low in fibre

Food B is:

• slightly higher in sugar
• lower in sodium
• high in fibre

Which is better?

There may not be one answer for every person.

The decision depends on:

• nutritional goals
• portion size
• overall diet
• health needs
• what else the person eats

Food evaluation requires looking at the whole nutritional profile.

---

Nutrient Density

A useful concept when evaluating foods is:

nutrient density

A nutrient-dense food provides substantial useful nutrients relative to its energy content.

These may include:

• protein
• fibre
• vitamins
• minerals
• essential fatty acids

 

 

 

6

Food labels can help identify some aspects of nutrient density.

---

Food Labels and a Balanced Diet

A food does not need to contain every nutrient.

For example:

Fruit may contain little protein.

Nuts may contain substantial fat.

Milk may contain relatively little fibre.

That does not automatically make these foods poor choices.

Foods work together as part of a diet.

Therefore:

evaluate the food + evaluate the portion + evaluate the overall diet

---

Labels Help With Specific Nutritional Needs

Different people may focus on different parts of a label.

Someone comparing protein sources may focus on:

protein

Someone trying to increase fibre may examine:

dietary fibre

Someone advised to monitor sodium may focus on:

sodium

Someone with an allergy may focus first on:

ingredients and allergen information

There is no single nutrient that everyone must always prioritize above all others.

---

Food Labels and Deficiency Prevention

Labels can help people identify foods containing particular nutrients.

For example:

A person looking for iron might compare:

iron content

Someone looking for calcium might compare:

calcium content

Someone looking for fibre might compare:

fibre content

This connects food-label reading with preventing nutritional deficiencies.

---

Food Labels and Long-Term Health

Food choices repeated over time contribute to overall dietary patterns.

Consider:

one meal

↓

daily choices

↓

weekly pattern

↓

long-term diet

↓

influence on health

Labels can therefore help people make informed repeated choices.

However, health is influenced by many other factors as well.

---

Common Mistake: Ignoring Serving Size

Label says:

100 kcal per serving.

Person eats:

3 servings.

Actual intake:

100 × 3 = 300 kcal

Always ask:

"How many servings am I actually consuming?"

---

Common Mistake: Comparing Different Quantities

Food A:

5 g sugar per 30 g serving

Food B:

6 g sugar per 50 g serving

You cannot fairly compare 5 g and 6 g without considering the different serving sizes.

Convert both to:

per 100 g

or another equal amount.

---

Common Mistake: Looking at Only One Nutrient

A product may be:

low sugar

but:

high sodium

Another may be:

high protein

but:

high saturated fat

Food evaluation should consider multiple pieces of information.

---

Common Mistake: Assuming More Vitamins Always Means Better

A food fortified with several vitamins may still contain large amounts of:

• added sugar
• sodium
• saturated fat

Added vitamins do not automatically make the overall product nutritionally balanced.

---

Common Mistake: Believing the Front of the Package

The front of a package is partly designed for:

marketing

The nutrition panel and ingredients list are designed to provide:

information

 

 

 

6

When the advertising and the nutritional data seem to tell different stories, examine the evidence carefully.

---

A Food Label Investigation

Choose two similar packaged foods.

For example:

• two cereals
• two yoghurts
• two breads
• two snack bars
• two soups
• two drinks

Record:

Information	Product A	Product B
Serving size
Energy
Protein
Total fat
Saturated fat
Carbohydrate
Sugars
Fibre
Sodium
First three ingredients

Then answer:

Which contains more sugar?

Which contains more fibre?

Which contains more protein?

Which contains more sodium?

Are the serving sizes the same?

Would your conclusions change if you compared them per 100 g?

Which product better fits a particular nutritional goal?

Explain your decision using evidence from the labels.

---

Did You Know?

A package that looks like one portion may contain more than one labeled serving.

 

 

 

6

If a bottle contains:

2.5 servings

and each serving contains:

8 g sugar

the entire bottle contains:

8 × 2.5 = 20 g sugar

Small print can make a large difference to the numbers.

---

Key Terms

• Food label: Information provided on food packaging about the product and its contents.
• Nutrition information panel: Section showing the amounts of energy and nutrients in a food.
• Serving size: Reference quantity used to calculate nutritional information.
• Portion: Amount of food actually eaten.
• Energy: Chemical energy supplied by food, commonly expressed in kcal or kJ.
• Calorie: Common food-energy unit; a food Calorie equals one kilocalorie.
• Kilojoule (kJ): Metric unit of energy.
• Total fat: Total quantity of dietary fat in a stated amount of food.
• Saturated fat: Type of dietary fat containing fatty acids without carbon-carbon double bonds.
• Carbohydrate: Macronutrient that includes sugars, starches, and—in some labeling systems—fibre.
• Total sugars: Total amount of sugars present in a food.
• Added sugars: Sugars added during manufacturing or preparation.
• Dietary fibre: Plant-derived material that supports digestive health.
• Protein: Nutrient providing amino acids for growth, repair and other functions.
• Sodium: Mineral involved in fluid balance, nerve function and muscle activity.
• % Daily Value: Percentage showing how much a serving contributes to a reference daily amount.
• Ingredients list: List of substances used to make a food.
• Allergen: Substance capable of triggering an allergic reaction.
• Fortification: Addition of nutrients to a food.
• Nutrient density: Amount of useful nutrition provided relative to energy content.
• Nutrition claim: Statement highlighting a particular nutritional characteristic of a food.

---

Key Relationships

Serving calculations:

amount consumed ÷ serving size = number of servings

Then:

nutrient per serving × number of servings = nutrient consumed

Comparison:

same quantity → fairer nutritional comparison

Percentage by mass:

nutrient mass ÷ total food mass × 100 = percentage

Energy:

carbohydrate ≈ 4 kcal/g

protein ≈ 4 kcal/g

fat ≈ 9 kcal/g

Food evaluation:

serving size + energy + nutrients + ingredients + dietary context → informed choice

---

Key Takeaways

• Food labels provide evidence about the nutritional composition of foods.
• Nutrition panels commonly provide information about energy, fat, carbohydrates, sugars, protein and sodium.
• Some labels also provide fibre, vitamins and minerals.
• Always check the serving size before interpreting the numbers.
• Serving size and the amount actually eaten may be different.
• Eating multiple servings means consuming multiple times the listed nutrients.
• Energy may be expressed in kilocalories or kilojoules.
• Calories alone do not determine the nutritional quality of a food.
• Total fat and saturated fat provide different information.
• Fat is an essential nutrient, but the amount and type matter.
• Total sugars can include naturally occurring and added sugars.
• "No added sugar" does not mean "sugar-free."
• Fibre is an important consideration when comparing many carbohydrate-rich foods.
• Sodium is an essential nutrient, but excessive intake can be a concern.
• Sodium and salt are related but are not the same measurement.
• % Daily Value indicates how much a serving contributes toward a reference daily amount.
• Individual nutritional requirements may differ from reference Daily Values.
• Per-100-g or per-100-mL values are especially useful when comparing similar products.
• Foods should be compared using equal quantities whenever possible.
• Ingredients are generally listed from greatest to least by weight.
• Ingredients lists can provide useful context that the nutrition panel does not show.
• Allergen information can be essential for food safety.
• Front-of-package claims do not provide the complete nutritional picture.
• "Reduced" does not necessarily mean "low."
• "Natural" does not automatically mean nutritionally balanced.
• A food advertised as "high protein" or "low fat" should still be evaluated using the full label.
• Comparing food labels requires mathematical skills such as multiplication, division, ratios and percentages.
• No single nutrient determines whether a food is a suitable choice.
• The usefulness of a food depends partly on portion size, individual needs and the rest of the diet.
• Food labels can help people choose foods that support particular nutritional goals.
• A useful rule is: check the serving → compare equal amounts → examine several nutrients → read the ingredients → consider the whole diet.

 

 

 

5. Energy Requirements and Healthy Living

 

 

 

7

Why Does the Body Need Energy?

Every living cell requires energy.

Even when you appear to be doing nothing, your body is carrying out thousands of processes.

Energy is needed for:

• muscle contraction
• active transport
• protein synthesis
• cell division
• growth
• tissue repair
• nerve impulses
• maintaining body temperature
• breathing
• circulation

Energy therefore supports both visible activities, such as running, and invisible processes, such as maintaining ion gradients across cell membranes.

Where Does Our Energy Come From?

The body's energy ultimately comes from:

food

The major energy-yielding nutrients are:

• carbohydrates
• lipids
• proteins

These nutrients contain stored chemical energy.

During digestion and metabolism, the body processes these nutrients so their energy can be transferred and used by cells.

 

 

 

6

Energy from Carbohydrates

Many dietary carbohydrates are digested into smaller sugars, including:

glucose

Glucose can be transported in the blood and used by cells during respiration.

Carbohydrate-rich foods include:

• rice
• bread
• pasta
• potatoes
• cereals
• fruit
• grains

Carbohydrates provide approximately:

4 kcal per gram

Energy from Lipids

Lipids are concentrated sources of energy.

They provide approximately:

9 kcal per gram

This is more than twice the energy provided by the same mass of carbohydrate or protein.

 

 

 

5

Lipids are particularly important for:

• long-term energy storage
• cell membranes
• insulation
• protection of organs
• absorption of fat-soluble vitamins

Energy from Proteins

Proteins provide approximately:

4 kcal per gram

However, proteins also have important structural and functional roles.

Proteins are used to make:

• muscles
• enzymes
• antibodies
• transport proteins
• receptors
• many cellular structures

Therefore, although protein can provide energy, it is also essential as a source of amino acids for building and maintaining the body.

Vitamins, Minerals, and Water

Vitamins, minerals, and water are essential nutrients.

However, they do not directly provide food energy.

For example:

iron

helps form haemoglobin.

vitamin D

contributes to calcium regulation.

water

provides a medium for chemical reactions and transport.

These substances help the body function, but they are not significant sources of calories.

Measuring Food Energy

Food energy is commonly measured using:

kilocalories (kcal)

or:

kilojoules (kJ)

A food Calorie, written with a capital C, is equivalent to:

1 kilocalorie

Approximately:

1 kcal = 4.184 kJ

Therefore:

500 kcal ≈ 2092 kJ

Comparing the Energy Nutrients

This explains why foods high in fat can contain substantial energy even when the portion is relatively small.

From Food to Cellular Energy

The process begins with food.

food

↓

digestion

↓

nutrient absorption

↓

transport

↓

cells

↓

cellular respiration

↓

energy transferred for cellular activities

 

 

 

5

The body does not simply "burn calories" like a fire.

It uses complex sequences of enzyme-controlled chemical reactions to transfer energy.

Cellular Respiration

A simplified equation for aerobic respiration is:

glucose + oxygen → carbon dioxide + water

During this process, energy is transferred from glucose and captured in forms that cells can use, particularly:

ATP

ATP stands for:

adenosine triphosphate

ATP acts as an immediate energy carrier inside cells.

What Is ATP Used For?

ATP provides energy for processes such as:

• muscle contraction
• active transport
• protein synthesis
• cell division
• movement of cellular structures
• maintenance of ion gradients

Therefore:

food energy → cellular respiration → ATP → cellular work

The Body Uses Energy All the Time

It is easy to think that energy is only used during exercise.

However, the body uses energy continuously.

Even while sleeping, energy is needed for:

• breathing
• heartbeat
• brain activity
• maintaining body temperature
• kidney function
• cellular repair
• metabolism

 

 

 

5

Basal Metabolic Rate

Basal metabolic rate (BMR) is the energy used to maintain essential body functions while the body is at rest under standardized conditions.

Energy is required for:

• breathing
• circulation
• brain function
• maintaining body temperature
• cellular processes
• organ function

For many people, basic metabolism represents a substantial part of total daily energy expenditure.

Physical Activity

Physical activity increases energy expenditure.

Examples include:

• walking
• running
• cycling
• swimming
• sports
• climbing stairs
• physical work
• household activities

The amount of energy used depends on factors such as:

intensity + duration + body size + type of activity

Exercise and Energy Expenditure

Compare:

sitting for 30 minutes

with:

running for 30 minutes

Running requires greater muscle activity.

Muscles require more ATP.

This increases the rate at which energy is transferred from stored fuels.

Therefore:

greater physical activity → greater energy expenditure

 

 

 

5

Digestion Also Requires Energy

The body also uses energy to:

• digest food
• absorb nutrients
• process nutrients
• store nutrients

This is sometimes called the:

thermic effect of food

Therefore, total energy expenditure includes more than just BMR and exercise.

Total Daily Energy Expenditure

A simplified model is:

Total daily energy expenditure = basal metabolism + physical activity + energy used to process food + other physiological demands

Growth, pregnancy, illness, and environmental conditions can also influence energy requirements.

Energy Requirements Are Different for Everyone

There is no single amount of energy that is correct for every person.

Energy requirements depend on factors such as:

• age
• sex
• body size
• body composition
• activity level
• growth
• pregnancy
• health
• environmental conditions

Two people can therefore have very different energy requirements.

Age

Energy requirements change throughout life.

Children and adolescents require energy for:

normal body functions + physical activity + growth

Adults require energy mainly for:

maintenance + activity

Older adults may have lower energy requirements if:

• muscle mass decreases
• physical activity decreases
• metabolic requirements change

However, individual variation is considerable.

Growth

Growing children and teenagers need energy to build:

• new cells
• muscles
• bones
• organs
• other tissues

 

 

 

7

Growth therefore increases nutritional requirements.

Growing bodies need both:

energy

and:

raw materials such as protein, minerals, vitamins and essential fats

Body Size

Larger bodies generally require more energy to maintain than smaller bodies.

One reason is that a larger body contains more tissue requiring:

• oxygen
• nutrients
• circulation
• temperature regulation
• cellular maintenance

However, body composition also matters.

Body Composition

Muscle tissue and fat tissue have different metabolic characteristics.

A person with more lean tissue may have a different resting energy requirement from another person of the same body mass with a different body composition.

Therefore:

body mass alone does not completely determine energy requirements.

Physical Activity Level

Activity level can strongly influence daily energy requirements.

Consider:

Person A: mostly sedentary day

Person B: walks frequently and plays sport

Person C: trains intensively for several hours

Their energy expenditures may be substantially different.

Therefore, energy intake that is appropriate for one person may not be appropriate for another.

Energy Balance

Energy balance describes the relationship between:

energy intake

and:

energy expenditure

A simplified model is:

energy intake ≈ energy expenditure

over time.

 

 

 

5

Positive Energy Balance

A positive energy balance occurs when:

energy intake > energy expenditure

The body has more energy available than it immediately requires.

Some excess energy can be stored.

Long-term substantial positive energy balance can contribute to increased body energy stores, including body fat.

Negative Energy Balance

A negative energy balance occurs when:

energy intake < energy expenditure

The body must use stored energy.

If this continues over time, body mass may decrease.

Short-term negative energy balance is common and does not automatically indicate a problem.

The important consideration is the long-term pattern and the individual's needs.

Energy Balance Changes Constantly

Energy intake and expenditure do not need to match perfectly every hour or even every day.

For example:

Monday:

intake > expenditure

Tuesday:

intake < expenditure

Wednesday:

approximately equal

The body can store and release energy.

Therefore, energy balance is best understood over:

longer periods of time

rather than individual meals.

Energy Storage

The body can store energy in several forms.

Glycogen

is a carbohydrate storage molecule found mainly in:

• liver
• skeletal muscles

Triglycerides

are stored mainly in adipose tissue.

 

 

 

4

Fat provides a particularly concentrated long-term energy reserve.

Exercise and Healthy Living

Physical activity does much more than increase energy expenditure.

Regular physical activity can support:

• cardiovascular health
• muscle strength
• bone health
• mobility
• metabolic health
• coordination
• mental well-being
• sleep

Different types of exercise provide different benefits.

Aerobic Exercise

Aerobic exercise involves sustained activity using large muscle groups.

Examples include:

• brisk walking
• running
• cycling
• swimming
• dancing

 

 

 

6

Regular aerobic activity can improve the ability of the cardiovascular and respiratory systems to deliver oxygen to working tissues.

Strength Exercise

Strength or resistance exercise challenges muscles against resistance.

Examples include:

• lifting weights
• resistance bands
• body-weight exercises
• climbing

Strength training can help maintain or increase:

• muscle strength
• muscle mass
• bone strength
• functional ability

A healthy activity pattern can include both aerobic and strength-based activities.

Exercise and the Cardiovascular System

During exercise:

muscles require more ATP

↓

respiration increases

↓

oxygen demand increases

↓

heart rate and breathing rate increase

This helps deliver:

• oxygen
• glucose
• other fuels

to working muscles.

It also helps remove:

• carbon dioxide
• heat
• metabolic products

Exercise and Bones

Bones respond to mechanical stress.

Weight-bearing and resistance activities can help stimulate bone maintenance.

Examples include:

• walking
• running
• jumping
• resistance training

 

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6

Bone health also depends on nutrition, including adequate:

• calcium
• vitamin D
• protein

Exercise and Mental Well-Being

Physical activity can also support mental well-being.

Regular activity is associated with benefits such as:

• improved mood
• reduced stress
• improved sleep
• better cognitive function

Exercise is therefore not only about:

burning calories

It affects many body systems.

Sleep Is Part of Healthy Living

Sleep is a fundamental biological requirement.

During sleep, the body continues important processes involving:

• brain function
• memory
• hormone regulation
• immune function
• tissue maintenance
• metabolism

 

 

 

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Adequate sleep is therefore part of a healthy lifestyle alongside nutrition and physical activity.

Sleep and the Brain

Sleep supports:

• learning
• memory consolidation
• attention
• decision-making
• emotional regulation

For students, inadequate sleep can make it more difficult to:

• concentrate
• remember information
• solve problems
• stay alert

This makes sleep directly relevant to academic performance.

Sleep and Physical Health

Sleep also interacts with:

• immune function
• metabolism
• appetite regulation
• cardiovascular health
• physical recovery

Chronic sleep deprivation can therefore influence health in several ways.

Sleep Requirements Change With Age

Sleep needs are not identical for everyone.

Children and teenagers generally require more sleep than adults because they are still developing.

Individual needs also vary.

The important principle is:

regular, sufficient, good-quality sleep supports normal physical and mental function.

Sleep Habits

Habits that can support healthy sleep include:

• keeping a reasonably consistent sleep schedule
• having a relaxing routine before bed
• keeping the sleeping environment comfortable
• limiting disruptive light and noise
• avoiding large amounts of caffeine late in the day
• allowing enough time for sleep

Healthy sleep is partly about both:

quantity + quality

Hydration

Water is essential for:

• blood volume
• chemical reactions
• transport
• temperature regulation
• normal cell function

Physical activity can increase water loss through:

sweating

 

 

 

6

Fluid requirements increase under conditions such as:

• exercise
• hot weather
• high humidity
• illness involving fluid loss

Temperature Regulation During Exercise

Working muscles release substantial heat.

To prevent excessive increases in body temperature, the body can increase:

sweating

When sweat evaporates:

thermal energy is transferred from the skin to the environment

This helps cool the body.

Adequate hydration supports this temperature-regulation system.

Healthy Eating and Energy

Healthy living does not simply mean minimizing calories.

The body requires sufficient energy for:

• normal metabolism
• physical activity
• growth
• repair
• reproduction
• immune function

Energy intake should therefore be considered alongside:

nutritional quality

A diet can provide plenty of energy while still lacking important nutrients.

Nutrient Density

Nutrient-dense foods provide useful nutrients relative to their energy content.

Examples can include:

• vegetables
• fruits
• whole grains
• legumes
• fish
• eggs
• nuts
• seeds

 

 

 

6

These foods can contribute:

• protein
• fibre
• vitamins
• minerals
• essential fats

Healthy Living Is a Combination of Behaviours

Long-term health is not determined by one behaviour.

It is influenced by patterns involving:

nutrition

physical activity

sleep

hydration

stress management

avoiding harmful substances

preventive healthcare

social and environmental factors

These factors interact with one another.

Lifestyle Factors Work Together

Consider:

regular exercise + insufficient sleep

Exercise is beneficial, but chronic sleep deprivation may interfere with recovery and well-being.

Consider:

balanced diet + no physical activity

Good nutrition is valuable, but regular movement provides additional benefits.

Consider:

exercise + balanced diet + adequate sleep

These habits can reinforce one another.

Sedentary Behaviour

Sedentary behaviour involves long periods of very low-energy activity while awake, such as:

• prolonged sitting
• long periods of screen use
• extended periods of inactivity

Regular physical activity is important, but reducing prolonged sedentary periods can also contribute to healthy living.

Simple strategies can include:

• walking during breaks
• standing periodically
• taking stairs
• incorporating movement throughout the day

Everyday Activity Matters

Physical activity does not have to mean organized sport.

 

 

 

6

Useful movement can include:

• walking to school or work
• cycling
• taking stairs
• household work
• gardening
• active recreation
• playing outside

Small amounts of movement accumulated throughout the day can contribute to overall activity.

Evaluating Lifestyle Habits

When evaluating a habit, ask:

Does it support physical health?

Does it support mental well-being?

Is it sustainable over time?

Does it interfere with sleep?

Does it provide adequate nutrition?

Does it encourage movement?

Could it cause harm if continued for years?

Long-term patterns matter more than isolated choices.

Case Study: Student A

Student A:

• eats a varied diet
• walks to school
• plays sport three times each week
• drinks water regularly
• usually gets sufficient sleep

These habits support several aspects of health simultaneously:

nutrition + activity + hydration + recovery

Case Study: Student B

Student B:

• frequently skips breakfast and lunch
• consumes most food late in the day
• sleeps five hours on many school nights
• rarely exercises
• spends much of the day sitting

Rather than focusing on one single behaviour, evaluate the pattern.

Potential areas for improvement include:

• more regular nutrition
• more sleep
• increased daily movement
• more consistent routines

The goal should be sustainable improvements rather than extreme changes.

Case Study: The Athlete

An athlete trains intensely for 90 minutes each day.

Their energy requirements may be higher because:

greater activity → greater energy expenditure

They may also require additional:

• carbohydrate
• fluids
• protein
• electrolytes, depending on conditions and duration

Simply eating the same amount as a much less active person may not meet their requirements.

Case Study: Exam Week

A student has exams and decides to study until 2:00 a.m. every night.

They believe:

more study time = better results

But reduced sleep may negatively affect:

• concentration
• memory
• alertness
• decision-making

This illustrates an important principle:

healthy habits can support learning as well as physical health.

Short-Term vs Long-Term Choices

One late night does not automatically cause poor health.

One unhealthy meal does not destroy a balanced diet.

One workout does not create physical fitness.

Health develops through:

repeated behaviours over time

Therefore, evaluate:

patterns

rather than:

isolated events

Avoiding Extremes

Healthy living is generally not about extreme restrictions or extreme exercise.

For example:

too little energy intake

can interfere with:

• growth
• recovery
• hormone function
• physical performance

while:

excessive energy intake over long periods

can contribute to increased body energy stores.

Similarly:

too little activity

can affect health,

while:

excessive training without adequate recovery

can also cause problems.

Balance matters.

Healthy Body Mass Is More Complex Than Calories Alone

Body mass is influenced by energy balance, but human health is more complicated than:

"calories in vs calories out."

Factors can include:

• appetite regulation
• genetics
• sleep
• hormones
• medications
• environment
• food availability
• physical activity
• body composition
• health conditions

Energy balance remains a useful scientific concept, but it should not be used to oversimplify individual health.

Exercise Is Not Punishment for Eating

Food provides energy and nutrients the body requires.

Exercise provides benefits including:

• stronger muscles
• cardiovascular fitness
• stronger bones
• improved mobility
• mental well-being

Therefore, exercise is better understood as:

a normal part of maintaining a healthy body

rather than simply a way to "burn off" food.

Long-Term Health

Lifestyle habits can influence the risk of chronic diseases.

Regular physical activity, adequate sleep, balanced nutrition, and avoiding harmful substances can contribute to lower risk of several long-term health problems.

 

 

 

6

However, health is also influenced by:

• genetics
• age
• environment
• healthcare access
• socioeconomic factors
• existing medical conditions

Lifestyle affects risk; it does not guarantee a particular outcome.

Connecting Energy to Respiration

This topic connects nutrition directly to cellular biology.

food

↓

carbohydrates

↓

glucose

↓

bloodstream

↓

cells

↓

cellular respiration

↓

ATP

↓

cellular work

For aerobic respiration:

glucose + oxygen → carbon dioxide + water + energy transferred

Connecting Exercise to Respiration

During exercise:

muscle activity increases

↓

ATP demand increases

↓

respiration rate increases

↓

oxygen and fuel requirements increase

↓

heart rate and breathing rate increase

This connects:

nutrition + respiration + circulation + breathing + movement

Connecting Exercise to Nutrition

After physical activity, the body may need to:

• restore glycogen
• repair muscle tissue
• replace fluids
• replace electrolytes
• continue normal metabolism

Nutrition and recovery therefore work together.

Exercise does not replace good nutrition, and nutrition does not replace exercise.

Connecting Sleep to Recovery

During sleep, the body continues:

• tissue repair
• protein synthesis
• hormone regulation
• memory processing
• immune-system activity

Therefore:

exercise → stress on tissues

nutrition → supplies materials

sleep → supports recovery processes

These systems are connected.

A Healthy Daily Pattern

A healthy day might include:

Morning

• nutritious breakfast
• water
• walking or other movement

Daytime

• balanced meals
• regular movement
• hydration

Afternoon

• exercise or active recreation

Evening

• balanced meal
• time to relax
• preparation for sleep

Night

• sufficient sleep

 

 

 

6

There is no single schedule that works for everyone.

The important idea is to build sustainable healthy patterns.

Evaluating Health Information

Health information appears everywhere:

• social media
• advertisements
• influencers
• news
• product packaging
• websites

Claims might include:

"This food burns fat."

"This supplement boosts energy."

"Never eat carbohydrates."

"This workout changes your body in seven days."

Scientific thinking requires evaluating such claims carefully.

Questions to Ask About Health Claims

Ask:

What evidence supports the claim?

Who produced the information?

Are they selling something?

Does the claim promise unrealistic results?

Does it describe risks and limitations?

Does it agree with established scientific evidence?

Is the claim based on one person's experience or systematic research?

Personal testimonials are not the same as scientific evidence.

Common Misconception: Calories Are Bad

Calories are units of energy.

The body needs energy to survive.

The issue is not whether food contains calories.

The important questions include:

• Does energy intake match the person's needs reasonably over time?
• Does the food provide useful nutrients?
• What is the overall dietary pattern?

Common Misconception: Exercise Only Matters for Weight

Exercise affects many aspects of health independently of body mass.

Benefits can include:

• improved cardiovascular function
• stronger muscles
• stronger bones
• improved insulin sensitivity
• improved mobility
• improved mental well-being
• better physical fitness

Body mass is only one possible outcome.

Common Misconception: More Exercise Is Always Better

Exercise provides many benefits, but the body also requires:

recovery

Excessive training without adequate:

• rest
• sleep
• nutrition
• recovery time

can reduce performance and increase injury risk.

Healthy training involves:

exercise + recovery

Common Misconception: Sleeping Less Gives You More Productive Time

Being awake longer does not necessarily mean being more productive.

Insufficient sleep can reduce:

• attention
• memory
• reaction time
• decision-making

Sleep should therefore be considered part of effective learning and performance.

Common Misconception: Healthy Living Requires Perfection

Healthy living does not require every meal, workout, or night of sleep to be perfect.

Long-term health is influenced much more by:

consistent patterns

than occasional exceptions.

A sustainable approach is usually more realistic than extreme short-term changes.

Did You Know?

Your brain requires substantial energy even when you are sitting still.

 

 

 

Thinking does not look like intense physical work, but neurons continuously require energy to:

• maintain ion gradients
• transmit electrical signals
• release neurotransmitters
• maintain cellular structures

This is another reminder that:

resting does not mean using no energy.

Key Terms

• Energy: Capacity to cause change or perform work.
• Kilocalorie (kcal): Unit commonly used to measure food energy.
• Kilojoule (kJ): Metric unit of energy.
• Metabolism: All chemical reactions occurring in the body.
• Cellular respiration: Chemical reactions that transfer energy from nutrient molecules.
• ATP: Adenosine triphosphate; an immediate energy carrier used by cells.
• Basal metabolic rate (BMR): Energy expenditure required to maintain essential body functions under standardized resting conditions.
• Energy intake: Energy obtained from food and drinks.
• Energy expenditure: Energy used by the body.
• Energy balance: Relationship between energy intake and expenditure.
• Positive energy balance: Energy intake exceeds expenditure.
• Negative energy balance: Energy expenditure exceeds intake.
• Glycogen: Storage form of carbohydrate in animals.
• Adipose tissue: Tissue specialized for storing fat and other functions.
• Physical activity: Body movement produced by skeletal muscles that requires energy.
• Exercise: Planned or structured physical activity intended to improve or maintain fitness.
• Aerobic exercise: Sustained activity relying substantially on aerobic energy pathways.
• Hydration: Maintaining adequate body water.
• Sedentary behaviour: Waking behaviour involving very low energy expenditure while sitting, reclining, or lying.
• Nutrient density: Amount of useful nutrition provided relative to energy content.
• Recovery: Processes that restore the body following physical or mental demands.
• Lifestyle: Pattern of behaviours and environmental factors affecting daily life and health.

Key Relationships

Food energy:

food → digestion → nutrients → cells → respiration → ATP

Aerobic respiration:

glucose + oxygen → carbon dioxide + water + energy transferred

Energy balance:

energy intake ↔ energy expenditure

Positive energy balance:

intake > expenditure → increased energy storage

Negative energy balance:

intake < expenditure → stored energy is used

Exercise:

greater muscle activity → greater ATP demand → greater energy expenditure

Recovery:

exercise + nutrition + hydration + sleep → recovery and adaptation

Healthy living:

balanced nutrition + physical activity + sufficient sleep + hydration + sustainable habits → support for long-term health

Key Takeaways

• The body requires energy continuously.
• Food provides chemical energy.
• Carbohydrates, lipids, and proteins can provide energy.
• Carbohydrates and proteins provide approximately 4 kcal per gram.
• Fat provides approximately 9 kcal per gram.
• Vitamins, minerals, and water do not directly provide food energy.
• Digestion makes nutrients available for absorption.
• Cells transfer energy from nutrients through metabolic processes including cellular respiration.
• ATP acts as an immediate energy carrier for cellular activities.
• Energy is required for movement, growth, repair, active transport, nerve impulses, and maintaining body temperature.
• The body uses energy even while resting and sleeping.
• Basal metabolism accounts for the energy required to maintain essential body functions.
• Physical activity increases energy expenditure.
• Total energy requirements vary between individuals.
• Age, growth, body size, body composition, activity, health, and other factors influence energy needs.
• Children and teenagers require energy for growth as well as normal metabolism.
• Energy balance compares energy intake with energy expenditure.
• Positive energy balance occurs when intake exceeds expenditure.
• Negative energy balance occurs when expenditure exceeds intake.
• Energy balance should be considered over time rather than meal by meal.
• The body stores carbohydrate as glycogen and large amounts of energy as fat.
• Regular physical activity supports cardiovascular, muscular, skeletal, metabolic, and mental health.
• Exercise provides benefits beyond changes in body mass.
• Both aerobic and strength activities can contribute to health.
• Sleep supports memory, learning, metabolism, immune function, and recovery.
• Adequate hydration supports circulation, metabolism, and temperature regulation.
• Exercise, nutrition, hydration, and sleep work together.
• Healthy living should focus on sustainable patterns rather than extreme short-term behaviours.
• Lifestyle influences long-term health risk but does not completely determine health outcomes.
• Genetics, environment, healthcare, and other factors also influence health.
• Health claims should be evaluated using scientific evidence rather than advertising or personal testimonials.
• Calories are a measurement of energy and are not inherently "good" or "bad."
• Healthy living is not about perfection.
• A useful overall model is: appropriate energy + nutritious food + regular movement + adequate sleep + hydration + recovery + sustainable habits = support for long-term health and well-being.