MAVO Year 4 · Nutrition and digestion · Section 12.2

Foods and nutrients

Foods and their nutrients

Foods are products we eat or drink, such as fruit, bread or milk. Their nutrients perform essential functions. Digestion breaks down some large food molecules into smaller molecules that can be absorbed. Other nutrients, such as water and mineral ions, can be absorbed without being digested first.

Six nutrient groups

Proteins: provide amino acids for growth, repair, enzymes and other functions. They can be used as fuel, but the body has no specialised protein reserve comparable to glycogen or body fat.
Carbohydrates: include sugars and starch, important energy sources. Glucose can be stored as glycogen; surplus energy can also contribute to fat storage.
Fats: supply energy, form reserves and contribute to structures such as membranes. Foods contain different mixtures of saturated and unsaturated fats. Replacing saturated fat with unsaturated fat generally benefits cardiovascular health. Plant origin does not automatically mean unsaturated: coconut and palm fats contain substantial saturated fat.
Water: forms much of blood and cytoplasm, acts as a solvent and transport medium, and supports temperature regulation.
Minerals: needed for many functions, including calcium in bones and iron in haemoglobin. Small amounts of fluoride help protect teeth.
Vitamins: organic micronutrients needed in small quantities, identified by names or letters such as A, B, C and D. Deficiency can cause health problems; excessive amounts of some vitamins can also be harmful.

Dietary fibre

Fibre consists mainly of plant substances not digested by human digestive enzymes. Some is fermented by gut microorganisms. Fibre supports bowel function and contributes to health. Different fibre types have different effects.

A balanced diet

Variety helps supply nutrients in suitable amounts. Both insufficient intake and excessive intake of particular substances can cause problems. The roles of nutrients overlap: fats are not only fuel, and minerals and vitamins do more than simply prevent disease.

Glossary

Protective nutrients: A school term for nutrients such as vitamins and minerals needed for normal function and prevention of deficiency.
Building nutrients: Substances used to form, maintain and repair cells and tissues.
Fuels: Substances broken down in respiration to release usable energy, including glucose and fats.
Proteins: Nutrients providing amino acids for structures and many functional molecules; they can also supply energy.
Carbohydrates: Substances including sugars, starch and cellulose, with energy, storage or structural roles; humans cannot digest cellulose with their own enzymes.
Minerals: Inorganic nutrients needed for functions such as building bones and making haemoglobin.
Unsaturated fats: Fats rich in unsaturated fatty acids, common in plant oils, nuts and fish; they can serve structural, fuel and storage roles.
Reserve substance: Material stored for later use, such as glycogen or fat.
Saturated fats: Fats rich in saturated fatty acids, found in many animal foods and some plant fats; replacing some with unsaturated fat can lower cardiovascular risk.
Fats: Energy-rich nutrients used for fuel, storage and body structures.
Vitamins: Organic nutrients needed in small amounts for normal functioning, often designated by letters and numbers.
Foods: Products people eat or drink.
Nutrients: Useful substances in food, grouped here as proteins, carbohydrates, fats, water, minerals and vitamins.
Dietary fibre: Food components not digested by human digestive enzymes, often from plants, supporting bowel function and other health processes.
Water: An essential nutrient acting as a solvent, transport medium and major component of the body.