Human Nutrition
1. Nutrients and Their Functions
Learning outcomes
- I can identify the major nutrients required by the human body.
- I can describe the functions of carbohydrates, lipids, proteins, vitamins, minerals, and water.
- I can explain why different nutrients are needed for health and growth.
- I can compare the roles of macronutrients and micronutrients.
- I can relate nutrient functions to specific body processes.
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
| Nutrient | Major Roles |
|---|---|
| Carbohydrates | Major source of energy |
| Lipids | Energy storage, membranes, insulation |
| Proteins | Growth, repair, enzymes and other proteins |
| Vitamins | Support and regulate body processes |
| Minerals | Structural and physiological functions |
| Water | Solvent, transport, reactions and temperature regulation |
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.
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
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
| Macronutrients | Micronutrients |
|---|---|
| Needed in relatively large amounts | Needed in relatively small amounts |
| Include carbohydrates, proteins and lipids | Include vitamins and minerals |
| Carbohydrates, proteins and lipids can provide energy | Generally do not provide energy directly |
| Often provide building materials as well as energy | Often regulate or support body processes |
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
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
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
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
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.
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.
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
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.
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
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.
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
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
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.
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.
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
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.
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:
| Nutrient | Possible Consequence of Significant Deficiency |
|---|---|
| Protein | Impaired growth and tissue maintenance |
| Vitamin C | Scurvy |
| Vitamin D | Poor bone mineralization; rickets in children |
| Iron | Iron-deficiency anaemia |
| Iodine | Impaired thyroid function |
| Water | Dehydration |
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.
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
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.
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
| Nutrient | Amount Needed | Main Functions | Example Sources |
|---|---|---|---|
| Carbohydrates | Large | Energy, fibre | Rice, bread, fruit |
| Lipids | Large | Energy storage, membranes, insulation | Oils, nuts, fish |
| Proteins | Large | Growth, repair, enzymes | Eggs, meat, beans |
| Vitamins | Small | Regulation and metabolic support | Fruits, vegetables, varied foods |
| Minerals | Small | Structural and physiological roles | Dairy, meat, vegetables, legumes |
| Water | Large | Transport, solvent, temperature control | Drinks and foods |
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
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.
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.