Digestion and Nutrition
4. Nutrients and Their Functions
Learning outcomes
- I can identify the major nutrients required by the human body.
- I can describe the functions of carbohydrates, proteins, and lipids.
- I can explain the importance of vitamins, minerals, and water.
- I can distinguish between macronutrients and micronutrients.
- I can explain how nutrients support growth, repair, and energy production.
Introduction
Every cell in the human body needs nutrients to survive. Nutrients provide the energy needed for movement, help build and repair body tissues, support growth, and regulate thousands of chemical reactions that keep the body functioning properly. Without a balanced supply of nutrients, the body cannot grow, stay healthy, or respond effectively to disease and injury.
There are six major classes of nutrients required by the human body: carbohydrates, proteins, lipids (fats), vitamins, minerals, and water. Each nutrient has a specific role, and together they provide everything the body needs to maintain life.
What Are Nutrients?
Nutrients are substances in food that the body needs for:
- Energy.
- Growth.
- Repair.
- Maintaining healthy body functions.
The six major nutrients are:
- Carbohydrates
- Proteins
- Lipids (fats)
- Vitamins
- Minerals
- Water
Each nutrient performs different but equally important functions.
Figure 1. The human body requires six major classes of nutrients to remain healthy.
Macronutrients and Micronutrients
Nutrients can be divided into two groups.
Macronutrients
Macronutrients are nutrients that the body needs in large amounts.
They include:
- Carbohydrates
- Proteins
- Lipids
- Water
Macronutrients provide energy or are needed in large quantities for normal body functions.
Micronutrients
Micronutrients are nutrients needed in small amounts.
They include:
- Vitamins
- Minerals
Although only tiny amounts are required, micronutrients are essential for health.
Carbohydrates
Carbohydrates are the body's main source of energy.
During digestion:
- Starch and sugars are broken down into glucose.
Cells use glucose during cellular respiration to release energy.
Examples of carbohydrate-rich foods:
- Bread
- Rice
- Pasta
- Potatoes
- Fruit
- Cereals
Unused glucose may be stored as glycogen in the liver and muscles.
Figure 2. Carbohydrates provide the body with its primary source of energy.
Proteins
Proteins are essential for:
- Growth.
- Repair.
- Building body tissues.
During digestion:
- Proteins are broken down into amino acids.
Amino acids are used to make:
- Muscles.
- Skin.
- Hair.
- Enzymes.
- Hormones.
- Antibodies.
Protein-rich foods include:
- Meat
- Fish
- Eggs
- Beans
- Lentils
- Dairy products
Lipids (Fats)
Lipids are an important source of long-term energy storage.
They also:
- Form cell membranes.
- Protect internal organs.
- Provide insulation.
- Help absorb vitamins A, D, E, and K.
Examples include:
- Oils
- Butter
- Nuts
- Seeds
- Avocados
Although fats are essential, excessive intake can contribute to health problems.
Figure 3. Lipids store energy, protect organs, and help build cell membranes.
Vitamins
Vitamins are organic substances required in small amounts.
They help regulate many body processes.
Examples include:
| Vitamin | Main Function |
|---|---|
| Vitamin A | Healthy vision and skin |
| Vitamin C | Wound healing and immune function |
| Vitamin D | Calcium absorption and healthy bones |
| Vitamin K | Blood clotting |
| B Vitamins. | Energy release and nervous system function |
Vitamin deficiencies can lead to disease.
Minerals
Minerals are inorganic nutrients required in small amounts.
Examples include:
| Mineral | Main Function |
|---|---|
| Calcium | Bones and teeth |
| Iron | Formation of haemoglobin in red blood cells |
| Potassium | Muscle and nerve function |
| Sodium | Fluid balance and nerve signalling |
| Magnesium | Muscle, nerve, and enzyme function |
Minerals cannot be produced by the body and must come from food.
Water
Water is the most abundant substance in the human body.
It performs many vital functions:
- Dissolves nutrients.
- Transports substances.
- Regulates body temperature.
- Removes wastes.
- Lubricates joints.
- Supports chemical reactions.
Adults should drink enough water each day to replace water lost through sweat, urine, and breathing.
Figure 4. Water is essential for transporting substances, regulating temperature, and supporting life processes.
Comparing Nutrient Functions
| Nutrient | Main Function |
|---|---|
| Carbohydrates. | Main source of energy |
| Proteins | Growth and tissue repair |
| Lipids | Long-term energy storage, insulation, cell membranes |
| Vitamins | Regulate body processes |
| Minerals | Support body structures and functions |
| Water | Transport, temperature regulation, chemical reactions |
A balanced diet provides all of these nutrients in appropriate amounts.
How Nutrients Support Life
Together, nutrients allow the body to:
- Produce energy.
- Build new cells.
- Repair damaged tissues.
- Support growth.
- Fight infections.
- Maintain healthy bones and muscles.
- Regulate body functions.
Different nutrients often work together.
For example:
- Vitamin D helps the body absorb calcium.
- Proteins build enzymes that digest carbohydrates and fats.
- Water transports glucose and amino acids to cells.
Figure 5. A balanced diet provides all the nutrients needed for growth, repair, and energy production.
Worked Example
Question
Match each nutrient to its primary function.
| Nutrient | Function |
|---|---|
| Carbohydrates. | Main source of energy |
| Proteins | Growth and repair |
| Lipids | Long-term energy storage |
| Calcium | Healthy bones and teeth |
| Vitamin C | Wound healing and immune function |
| Water | Transport of substances and temperature regulation |
Real-World Connection
A balanced breakfast containing whole-grain cereal, milk, fruit, and nuts provides several important nutrients. The carbohydrates supply glucose for energy, the protein supports growth and repair, the healthy fats provide long-term energy, the vitamins and minerals support body functions, and the water in food and drinks helps maintain hydration. Eating a variety of foods helps ensure the body receives all the nutrients it needs.
Did You Know?
Water makes up about 60% of an adult's body mass. Blood, muscles, the brain, and even bones contain significant amounts of water. Because the body constantly loses water through breathing, sweating, and urination, it must be replaced regularly to maintain normal body functions.
Key Terms
Carbohydrate – A nutrient that provides the body's main source of energy.
Lipid – A nutrient that stores energy, forms cell membranes, and provides insulation.
Macronutrient – A nutrient required by the body in relatively large amounts.
Micronutrient – A nutrient required by the body in relatively small amounts.
Mineral – An inorganic nutrient needed for healthy body functions.
Nutrient – A substance in food that supports growth, repair, energy production, and body functions.
Protein – A nutrient made of amino acids that is needed for growth and tissue repair.
Vitamin – An organic nutrient required in small amounts to regulate body processes.
Water – A nutrient that acts as a solvent, transport medium, temperature regulator, and reactant in many biological processes.
Key Takeaways
- The human body requires six major nutrients: carbohydrates, proteins, lipids, vitamins, minerals, and water.
- Carbohydrates, proteins, lipids, and water are macronutrients, while vitamins and minerals are micronutrients.
- Carbohydrates provide the body's main source of energy.
- Proteins support growth, repair, and the production of enzymes and hormones.
- Lipids provide long-term energy storage, insulation, and form cell membranes.
- Vitamins, minerals, and water regulate body processes and help maintain health.
- A balanced diet supplies all the nutrients needed for energy production, growth, tissue repair, and normal body function.