Why does the body need vitamins, minerals and water in small amounts?
Fat-soluble and water-soluble vitamins, major minerals and trace elements, water and dietary fibre: their functions, sources and the effects of deficiency.
A focused answer on micronutrients for AQA GCSE Food Preparation and Nutrition, covering fat-soluble and water-soluble vitamins, minerals and trace elements, water and dietary fibre and their deficiency effects.
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What this dot point is asking
AQA wants you to know the functions, food sources and deficiency effects of the main vitamins and minerals, and the role of water and dietary fibre. You should be able to group vitamins into fat-soluble and water-soluble.
Fat-soluble vitamins (A, D, E, K)
- Vitamin A (retinol/beta-carotene): needed for good vision in dim light, healthy skin and a strong immune system. Sources: liver, oily fish, dairy, carrots. Deficiency causes night blindness.
- Vitamin D: helps the body absorb calcium for strong bones and teeth. Sources: oily fish, eggs, fortified foods, and sunlight on the skin. Deficiency causes rickets in children and osteomalacia in adults.
Water-soluble vitamins (B group and C)
- Vitamin B group (e.g. thiamin, riboflavin, niacin, B12, folate): help release energy from food and keep the nervous system healthy. Folate is vital in early pregnancy. Deficiency of B12 or folate causes anaemia.
- Vitamin C: needed for healthy connective tissue, wound healing and absorbing iron, and acts as an antioxidant. Sources: citrus fruit, berries, peppers, potatoes. Deficiency causes scurvy.
Minerals and trace elements
- Calcium: strong bones and teeth, blood clotting and muscle function. Sources: milk, cheese, leafy greens. Deficiency causes weak bones and poor teeth.
- Iron: forms haemoglobin in red blood cells to carry oxygen. Sources: red meat, leafy greens, fortified cereals. Deficiency causes anaemia (tiredness, pale skin).
- Sodium (from salt): controls the body's water balance and nerve function. Too much raises blood pressure.
- Trace elements are needed in tiny amounts: iodine for the thyroid and fluoride for strong tooth enamel.
Why deficiencies have specific effects
Each micronutrient has a defined role, so a shortfall produces a specific condition rather than general illness. Too little vitamin D means calcium is poorly absorbed, so bones soften: this causes rickets (bowed legs) in children and osteomalacia in adults. Too little vitamin C weakens connective tissue (it is needed to make collagen), causing scurvy with bleeding gums and slow wound healing. Too little iron reduces haemoglobin, causing anaemia with tiredness and pale skin, which is a particular risk for teenage girls and women because iron is lost in menstruation. Too little iodine impairs the thyroid gland, which controls metabolism. Linking the missing nutrient to the right named condition is exactly what AQA rewards.
Water and dietary fibre
Water makes up about two thirds of the body. It controls body temperature through sweating, transports nutrients and oxygen in the blood, removes waste in urine, and is the medium for digestion and chemical reactions. Adults are advised to drink around 6 to 8 glasses (about 1.5 to 2 litres) of fluid a day, more in hot weather or when exercising. Too little causes dehydration, with headaches, tiredness, poor concentration and dark, concentrated urine.
Try this
Q1. Name the fat-soluble vitamins and state one difference between them and water-soluble vitamins. [3 marks]
- Cue. A, D, E, K; they can be stored in the body, unlike B and C.
Q2. Explain why a teenage girl might be advised to eat more iron-rich foods. [2 marks]
- Cue. Iron makes haemoglobin; girls lose iron through menstruation, so deficiency can cause anaemia.
Exam-style practice questions
Practice questions written in the style of AQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AQA 20196 marksExplain the functions of calcium and iron in the body, naming a good source and the effect of deficiency for each. (Paper 1, Section B)Show worked answer →
Calcium is needed to build and maintain strong bones and teeth, and also for blood clotting and muscle function. A good source is milk, cheese or yoghurt (and fortified plant milks). Deficiency leads to weak bones and poor teeth, and over time osteoporosis. Vitamin D is needed alongside it because it helps the body absorb calcium.
Iron is needed to make haemoglobin in red blood cells, which carries oxygen around the body. Good sources are red meat, leafy green vegetables and fortified cereals. Deficiency causes anaemia, with tiredness, pallor and shortness of breath. Top-band answers (5 to 6 marks) give function, source and deficiency clearly for each mineral.
AQA 20224 marksExplain why water-soluble vitamins are easily lost during food preparation and cooking, and suggest how a cook can reduce this loss. (Paper 1, Section A)Show worked answer →
Water-soluble vitamins (the B group and vitamin C) dissolve in water and are also destroyed by heat and by exposure to air (oxidation), so they leach into cooking water and break down when food is boiled for a long time or cut early.
A cook can reduce loss by steaming rather than boiling, using only a little water (and using it in a sauce or gravy), cooking for the shortest time, preparing vegetables just before cooking, and serving promptly. Markers reward the reason (soluble, heat sensitive, oxidise) plus practical reduction methods.
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Sources & how we know this
- AQA GCSE Food Preparation and Nutrition (8585) specification — AQA (2016)