The functions, food sources and deficiency or excess effects of carbohydrates, proteins, fats, vitamins, minerals and water in supporting health

What this dot point is asking

This dot point asks you to know the role of each nutrient, name reliable food sources, and explain the consequences of deficiency or excess. Strong answers connect a nutrient to a clear body function and to a specific dietary source.

Macronutrients

Carbohydrates are the body's main and preferred energy source, supplying about 16 kilojoules per gram. Complex carbohydrates such as wholegrains, legumes and starchy vegetables release energy slowly and add fibre, while simple sugars give quick energy. Too few carbohydrates leaves the body short of energy and forces it to break down fat and protein for fuel. A consistent excess of refined carbohydrates is linked to weight gain and type 2 diabetes.

Proteins build and repair body tissue and make enzymes, hormones and antibodies. They supply about 17 kilojoules per gram but are used for energy only when carbohydrate and fat are insufficient. Animal sources (meat, eggs, dairy, fish) provide all essential amino acids; plant sources (legumes, tofu, nuts, grains) can be combined to do the same. Protein deficiency impairs growth, immunity and wound healing.

Fats are the most energy-dense macronutrient at about 37 kilojoules per gram. They store energy, insulate the body, protect organs and carry the fat-soluble vitamins A, D, E and K. Unsaturated fats (olive oil, avocado, oily fish) support heart health, while excess saturated and trans fats raise the risk of cardiovascular disease.

Micronutrients

Vitamins are needed in small amounts to regulate body processes. They are either water-soluble (B-group and C, not stored, needed regularly) or fat-soluble (A, D, E, K, stored in body fat). Vitamin C supports immunity and helps absorb iron; vitamin D supports calcium absorption and bone health.

Minerals are inorganic elements with specific roles. Calcium builds bones and teeth and helps muscles and nerves work. Iron forms haemoglobin, which carries oxygen in the blood. Sodium helps regulate fluid balance, but excess sodium raises blood pressure.

Water

Water makes up around 50 to 70 per cent of body weight. It transports nutrients and wastes, regulates body temperature through sweating, lubricates joints and is the medium for almost every chemical reaction in the body. Even mild dehydration reduces concentration and physical performance; severe dehydration is life-threatening.

Matching nutrients to life stages and groups

Many exam questions give a specific person or group, so you must link nutrients to needs:

• Infants and young children: high energy and protein for rapid growth; iron and calcium for blood and bone development.
• Adolescents: increased energy, protein, calcium for the bone-building growth spurt, and extra iron for girls due to menstruation.
• Pregnant and breastfeeding women: more folate (to prevent neural tube defects), iron, iodine, calcium and overall energy.
• Older adults: often lower energy needs but continued or higher needs for calcium and vitamin D (bone health), protein (to limit muscle loss) and fibre and fluid (digestion).

Pairing the nutrient with the group's specific need, rather than listing nutrients in general, is what earns the application marks.

When answering, always pair a nutrient with a function and a food source, and if the question asks about a life stage or group, link the nutrient to that group's needs - for example, extra iron for adolescent girls or extra calcium for growing children and older adults. That targeted application is what separates a top answer from a generic list.