It promotes calcium and phosphorus absorption from the digestive system and aids the deposition of these minerals on to the bones.
Cholesterol damaged by free radicals can build up on artery walls and cause heart attacks and strokes. It's also vital for the optical nerves.
Made in the body, Vitamin K is needed to produce proteins which help to use calcium in formation and maintenance of strong bones and teeth. 99 per cent of the body's calcium is found in the bones and teeth where it is laid down on a protein matrix.
Part of blood haemoglobin, which transports oxygen to cells. Poor iron balance reduces concentration and increasing risk of infection.
If intake is low, extra vitamin A may help fight viral and bacterial infections. Under a doctor's supervision, high doses can treat acne in young people.
Women of childbearing age should take 400 micrograms supplement daily to reduce risk of spina bifida. Low levels can cause tiredness.
Vegans, whose diets are often low in B12, can experience fatigue and low energy levels. Can contribute to depression and disturbed sleep in adults.
Many women find 50-250mg supplements daily, improve mood swings and depression associated with PMS. A lack can cause adult tiredness.
Low intake can contribute to impaired immune system and to skin complaints such as coldsores and colds. Smokers need more than 100mg a day.
Deficiencies in children can help cause rickets, which weakens bones. Low intakes in women over 40 can contribute to osteoporosis.
Vitamin E may reduce the risk of angina in older people and 'intermittent claudication', a circulatory problem in smokers. It may also help PMS sufferers.
Low levels may affect bone strength and women who experience heavy periods. Establishes good blood clotting in babies.
Deficiencies associated with poor quality or brittle bones. Supplements can help. Those with magnesium may relieve PMS problems.
Can cause anaemia, leading to poor concentration and fatigue. Teenage girls and women before the menopause are most at risk.
Herrings, mackerel, egg yolks and liver. Carrots, sweet potatoes and mangoes contain beta carotene, which the body can convert into vitamin A.
Fortified breakfast cereals and bread, liver, black-eyed beans, Brussels sprouts, peanuts, spinach, broccoli, chickpeas.
Liver, red meat, game, fish, eggs, fortified breakfast cereals, fortified yeast extract, brewers yeast.
Wheatgerm, wheatbran, liver, cod, turkey, beef, bananas, Brussels sprouts, cabbage, mangoes, avocados and potatoes
Berries, citrus fruits and juices, papaya, guava, peppers, dark green vegetables.
Fresh tuna, sardines, salmon, cheddar cheese, eggs, margarine.
Wheatgerm oil, sunflower oil, sunflower seeds, hazelnut, almonds, pinenuts, sweet potatoes, spinach, muesli.
Broccoli, Brussels sprouts, green cabbage, yoghurt, alfalfa, egg yolk, kelp.
Skimmed milk, cheddar cheese, sesame seeds, tahini, tofu, canned sardines with bones, dried figs, dark green vegetables, baked beans.
Red meat, oily fish, crab, clams, venison, fortified breakfast cereals, sesame seeds, dried apricots, dark green leafy vegetables.
Adult Recommended Daily Amount (RDA): 800 micrograms. Large intakes of vitamin A are toxic and pregnant women should avoid supplements.
The adult RDA is 200 micrograms. High intake over time may interfere with zinc absorption and mask vitamin B12 deficiency.
The RDA is 1 microgram. No side-effects of too much B12 are known although the safe upper limit has been set at 3,000mcg a day from supplements.
RDA is 2mg. The body only absorbs around 100mg at one time. Extremely large doses may cause nerve damage. RDA is 60mg. Recent research suggests 'mega dosing' may be harmful. Over 2,000mg may cause cramps, diarrhoea, bloating, and kidney stones.
RDA 5mcg. Body regulates any extra vitamin D made from supplements, but taking 25-50mcg supplements can cause nausea and fatigue. RDA is 10mg. It is hard to overdose as it's a fat-soluble vitamin. Blood pressure or heart disease cases should take high doses under medical supervision.
As it's made naturally, most people don't need supplements. 1mcg is considered a safe intake.
The RDA is 800mg a day. More than 1,500mg a day may lead to calcium deposits in the kidneys and artery walls with prolonged use.
RDA is 14mg. Prolonged high intakes can be harmful. Excessive amounts can result in increased risk of heart disease and infection.
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