Uses in the body: needed for healthy skin, hair, nerves and bone marrow. Also helps to metabolise carbohydrate and protein to provide energy. Is absorbed from food and also produced by bacteria in the intestines.
Signs of deficiency: weakness, fatigue, skin irritation, cradle cap in babies, hair loss, poor appetite, depression. Long-term antibiotic use can cause biotin deficiency, as can consuming too much raw egg white.
Therapeutic uses: skin, nail and hair problems, including alopecia. An important nutrient for people on iron supplements, as the two nutrients are closely linked, and for those taking antibiotics or other medicines which can affect biotin production in the intestines. Athletes may benefit as they're often deficient in this nutrient.
Dietary sources: wholegrains (wholemeal bread, brown rice, bran cereals), egg yolk, nuts, beans, peas, cauliflower, liver, kidney, fish.
Recommended daily allowance: 150Âµg
Typical therapeutic daily dose: 500Âµg to 1,500Âµg
Daily intake shouldn't exceed: 2,500Âµg
Cautions: no contraindications, but keep to recommended dosage.
Best taken: with food at breakfast and lunch/dinner for split dose.
Uses in the body: important for healthy blood vessels, muscles, gums, bones and teeth. It's a powerful antioxidant and helps the body to fight infection because of its antiviral, antibacterial and immune-boosting effects. Helps wound healing and is involved in collagen production for healthy skin, the metabolism of cholesterol and the absorption of iron.
Signs of deficiency: poor skin and hair, bleeding, swollen gums, bruising, scurvy.
Therapeutic uses: poor skin and hair, wounds slow to heal, constant infections, colds and flu, bleeding gums, scurvy. Heavy smokers and drinkers, the elderly and those taking the contraceptive pill or antibiotics can especially benefit from additional vitamin C.
Dietary sources: fresh fruit and vegetables and their juices, especially guava fruit, kiwi fruit, currants, Brussels sprouts and peppers. Is easily destroyed in cooking.
Recommended daily allowance: 60mg
Typical therapeutic daily dose: 500mg to 2,000mg
Daily intake shouldn't exceed: 2,000mg
Cautions: high doses (1,000mg and above) can sometimes cause diarrhoea.
Best taken: in split doses of 500mg or in a time-release capsule between meals or with food. Buffered forms of vitamin C (magnesium or calcium ascorbate) are preferable to ascorbic acid, which can cause stomach upsets. Supplements that also contain bioflavonoids assist the absorption and availability of vitamin C.
Uses in the body: essential in the metabolism of calcium, for normal development of bones and nerves and healthy heart function.
Signs of deficiency: rickets (in children), joint pain, bone deformities, poor growth.
Therapeutic uses: the elderly or institutionalised, anyone not exposed to sunlight or people who've moved from a normally sunny climate to a dull one may benefit, as may vegans, people on long-term low-fat diets and those unable to absorb vitamin D or calcium.
Dietary sources: dairy produce (not low-fat), oily fish, cod liver oil, egg yolk, fortified margarines. However, the main source is action of sunlight on the skin.
Recommended daily allowance: 5Âµg
Typical therapeutic daily dose: vitamin D is rarely taken as a supplement, but under professional supervision doses of up to 10Âµg may be given.
Daily intake shouldn't exceed: 10Âµg
Cautions: not to be taken by those on certain types of medication or diuretics for heart problems. Consult your GP for advice. Toxic if taken in large doses; a daily intake of more than 600Âµg has been shown to have adverse effects on the liver where this nutrient is stored.
Best taken: have regular exposure to sunlight (remembering skin protection against UV light) or seek professional advice over supplementation.
Uses in the body: essential for healthy heart function, circulation and functioning of the sexual organs. It also strengthens immune function, is antioxidant and protects cells from free radicals (oxidising substances that damage and kill off healthy cells). Helps heal skin and scar tissue, reduces inflammation.
Signs of deficiency: no real deficiency signs
Therapeutic uses: cardiovascular disease, poor circulation (especially in the legs of smokers and diabetics), PMS, menstrual pain, menopausal flushes, joint and muscle pain and inflammation, stroke victims (but see 'Cautions'), eczema and dry skin, asthma, premature babies (who are often vitamin E deficient).
Dietary sources: seed oils, wheatgerm oil, olive oil, nuts and seeds, soya beans, avocados, pulses and beans, margarines, egg yolk, wholewheat flour and grains, leafy green vegetables.
Recommended daily allowance: 10mg
Typical therapeutic daily dose: 67mg to 670mg; doses of 200mg to 400mg are most common
Daily intake shouldn't exceed: 800mg
Cautions: high doses (above 670mg) can be toxic and cause blood thinning, so shouldn't be used by people taking anti-clotting medication such as warfarin or heparin. People with high blood pressure should start on a low dose and increase gradually under professional supervision. Diabetics should have their dosage monitored carefully as vitamin E can affect insulin requirements.
Best taken: in the form of natural-source vitamin E, d-alphatocopherol, with food. People with vitamin E absorption problems may be given the supplement by injection or in water-soluble form.
Uses in the body: essential for growth and development of cells and normal function of nervous system (in conjunction with vitamin B12). Also helps to regulate histamine levels and is vital for normal neural tube development in the foetus.
Signs of deficiency: lethargy, anaemia, shortness of breath, cracking of the corners of the mouth and sore tongue (although these two symptoms can also be due to iron or B vitamin deficiency), depression, nerve damage, neural tube defects (such as spina bifida) in babies.
Therapeutic uses: essential for all women planning pregnancy, during pregnancy and when breastfeeding, for dairy allergic infants fed on goats' milk (which is very low in folic acid), for people suffering from irritable bowel problems, depression, alcoholism, mental illness or the early stages of Alzheimer's disease.
Dietary sources: leafy green vegetables (especially spinach and curly kale), sprouts, broccoli, brewer's yeast, wholegrain cereals, liver, kidney, pulses, oranges.
Recommended daily allowance: 200Âµg
Typical therapeutic daily dose: 400Âµg is advised for all women planning pregnancy and up to the end of week 12 of pregnancy.
Daily intake shouldn't exceed: 400Âµg, although women who've already had a child with a neural tube defect and who wish to become, or are already, pregnant, may be advised to take 5mg (5000Âµg). Consult your GP for further advice.
Cautions: large intake (400Âµg a day over many months) can mask symptoms of a vitamin B12 deficiency and anaemia.
Best taken: daily with food, together with a B12 or B-complex supplement and with iron.
Uses in the body: regulates blood clotting. Is taken in through food and also produced by bacteria in the small intestine.
Signs of deficiency: bleeding disorders.
Therapeutic uses: may be required by newborns who are deficient and not yet able to produce bacteria in the gut, especially if the mother takes anti-epilepsy medication.
Dietary sources: cauliflower, green vegetables (especially kale, spinach, Brussels sprouts and broccoli), soya beans, potatoes, meat, green tea.
Recommended daily allowance: 80Âµg
Usually obtained from food but often given routinely to newborn babies as a 1mg dose in the first few hours of life to prevent haemorrhaging.
Cautions: no known maximum dosage, but excess intake should be avoided. People on anticoagulant medication shouldn't take vitamin K.
Best taken: obtained from food, produced in the gut or supplemented orally or by injection.