Types of supplements - information supplied by bbc health

Supplements are available in tablet, capsule, powder and liquid tincture form.

• If you have difficulty swallowing tablets you can crush them.
• If using capsules, try to obtain non-gelatine ones. Check the manufacturer's label.
• Powders and liquids are particularly suitable for children, the elderly and anyone convalescing, as they're easily absorbed by the body.
• Try to obtain supplements with the least amount of fillers, coatings and artificial colourings and those with natural, as opposed to synthetic, ingredients.

Dosages and RDAs

Recommended dosages for nutrients should be followed carefully. With supplements it's not the case that more is better; exceeding recommended doses can be dangerous. However, therapeutic doses are usually significantly higher than official recommended daily allowances (RDAs).

RDAs have been compiled as guidelines for 'average' people, yet they vary from country to country and don't take account of individual needs.

Our lists contain the typical range of therapeutic doses used by nutritional therapists as well as RDAs and maximum recommended dosages for reference. Dosages for children are always much lower than for adults, and men may require slightly larger doses than women. If in doubt, seek advice from a nutritional therapist.

Minerals tend to interact with each other and other nutrients and toxins. It's important to take this into account when supplementing your diet. For example, zinc can interfere with iron and copper absorption.

Store all nutrients in a cool, dry place and safely out of reach of children. Always read the label and check with a qualified practitioner or your GP if you have any doubts.

Vitamin A

(Vitamin A refers to a group of fat-soluble substances, including retinol, retinal and carotenoids, found only in animal produce. Another substance that converts into vitamin A in the body is beta-carotene, which is water-soluble and found in vegetables and fruits.)

Uses in the body: essential for the development of healthy bones, skin and eyesight, particularly night vision; strengthens the immune system, increasing resistance to infection.

Signs of deficiency: night blindness (difficulty seeing in poor light), dry skin, poor growth and development.

Therapeutic uses: skin conditions such as eczema, acne and psoriasis, night blindness, ulcers, respiratory, menstrual and urinary problems; may also play an important role in cancer prevention.

Dietary sources: liver, kidney, oily fish, cod liver oil, dairy produce, eggs and margarine; beta-carotene is found in orange, yellow and dark green vegetables and fruit, such as carrots, yellow bell peppers (capsicum), broccoli, spinach and watercress.

Cautions: not to be taken if pregnant or planning a pregnancy. Very high doses (above 9,000mg) can cause toxicity, signs of which include dry, scaly skin, fatigue, bone and joint pains and headache and require immediate medical attention. Discontinuation normally brings relief without further treatment.

Best taken: with food at breakfast and at lunch/evening meal for split doses.

Vitamin B1

(Thiamin)

Uses in the body: essential for carbohydrate metabolism, energy release and healthy heart, brain, nervous system, muscle function.

Signs of deficiency: extreme weakness (such as beri-beri in developing countries with poor diet), depression, numbness and tingling in the extremities, poor memory, headache, disturbed sleep.

Therapeutic uses: especially useful for those who smoke or drink heavily, do strenuous physical work, have a diet high in sugar and refined carbohydrates, have heart problems or those who are breastfeeding, on a growth spurt or under a lot of stress.

Dietary sources: brown, unpolished rice, wholegrains, wholewheat flour, brewer's yeast, yeast extract, nuts, beans, peas, cereals, potatoes, pork.

Cautions: not to be taken by people with kidney disease or children under 12 years. Toxicity is rare but has occasionally occurred in people receiving repeated injections of B1.

Best taken: in a B-complex, as it works together with other B vitamins, in a yeast-free form with breakfast. Very ill or alcohol-dependent people may be given B1 by injection for maximum absorption.

Vitamin B2

(Riboflavin)

Uses in the body: promotes normal growth and development, helps release energy from food, maintains health of mucus membranes. Is also needed for healthy skin, eyes and nervous system; plays a role in fertility.

Signs of deficiency: dry skin, cracked lips, red and flaky skin especially round nose and eyes, sore mouth and tongue, eye irritation and light sensitivity, poor concentration and memory, burning sensation in feet.

Therapeutic uses: pregnant and breastfeeding women, those on the contraceptive pill or oestrogen replacement therapy, young people during growth spurts, the elderly, athletes, people on high-protein diets or those suffering from stress or alcohol or drug abuse. People with mouth ulcers and gastric ulcers may also benefit.

Dietary sources: beef or lamb's liver, wild rice, wholewheat pasta, soya milk, wholegrain cereals, brewer's yeast, yeast extract, pulses, seeds, milk and other dairy produce. Can be destroyed if foods left in strong sunlight.

Cautions: shouldn't be taken at the same time as antibiotics (erythromycin and tetracycline) or methotrexate (an anti-cancer drug) as it interferes with their absorption. Not suitable for people with kidney disease or children under 12. May cause urine to turn bright yellow (to overcome this, increase daily fluid intake). Diuretics can increase the need for B2.

Best taken: with breakfast. A yeast-free form is best for those sensitive to yeast infections.

Vitamin B3

Uses in the body: the several forms of B3 - nicotinic acid (also known as niacin) and nicotinamide - assist with the function of the digestive and nervous systems. They play a role in food metabolism and energy release, as well as the formation of red blood cells and healthy skin.

Signs of deficiency: irritability, fatigue, poor memory, headache, dry skin, poor appetite, mouth ulcers, emotional instability, mental changes. Severe deficiency (now rarely seen) leads to a condition known as pellagra, which is characterised by very dry, cracked skin.

Therapeutic uses: dizziness, PMS, tinnitus, arthritis and in the treatment of burns, alcohol addiction, high cholesterol, mental problems and hyperthyroid (this requires medical supervision). Useful for athletes, the elderly and people suffering from stress.

Dietary sources: meat, fish, dairy produce, fish, fortified cereals, wholemeal bread, brewer's yeast, yeast extract, nuts, seeds, soya beans, potatoes, dried fruit, tomatoes, peas.

Cautions: take under supervision if pregnant or breastfeeding. Don't take if suffering from kidney disease or if a child under 12. Intakes of 150mg and above can lead to facial flushing, which is harmless but annoying. Intakes of more than 3,000mg can cause liver problems.

Best taken: in a yeast-free form with breakfast. Usually found in supplements in the form of nicotinamide.

Vitamin B5

(Pantothenic acid)

Uses in the body: needed for normal growth and brain activity, for formation of stress hormones and healthy adrenal gland function, for normal hair pigment and hair growth. Also plays a role in food metabolism.

Signs of deficiency: fatigue, weakness, headache, muscle cramps, poor coordination, numbness and tingling, depression, nausea, vomiting, abdominal cramps.

Therapeutic uses: to combat stress, as an adrenal support, for those taking the Pill, HRT or who drink and smoke a lot. Also used to relieve headache, insomnia, arthritis, food intolerance, hair problems and bruxism (teeth grinding).

Dietary sources: peanuts, liver, kidney, avocado, mushrooms, seeds and other nuts, pumpkin, egg yolks, dairy produce, dates, fish, chicken, wholegrain cereals and bread, dates, bananas.

Cautions: none known at recommended usage. Not suitable for children under 12.

Best taken: in a yeast-free form with breakfast. Usually found in supplements in the form of calcium pantothenate or magnesium pantothenate, which provides both magnesium and B5.

Vitamin B6

(Pyridoxine)

Uses in the body: essential for healthy red blood cells, metabolism, digestion and nervous system. Also helps to maintain fluid balance.

Signs of deficiency: irritability and nervousness, flaky skin around eyes, nose and mouth, sore tongue.

Therapeutic uses: morning sickness, PMS, insomnia and mild forms of anxiety and depression. Also recommended for women taking the contraceptive pill or HRT long-term, as these can lead to depletion of B6.

Dietary sources: wholegrains (breakfast cereals - especially muesli, bran flakes and porridge oats - brown rice and brown bread), wheatgerm, brewer's yeast, nuts and seeds, lentils, potatoes, baked beans, soya beans, bananas, white fish, meat. Considerable losses of B6 can occur during cooking.

Cautions: not to be taken by children under 12. If pregnant, it's best to get professional advice on dosage. High doses of B6 (100mg and above) can cause side effects including numbness and tingling in the fingers and toes. Discontinuation brings relief.

Best taken: with food at breakfast and at lunch/evening meal for split doses, as a time release-tablet, as part of a B-complex supplement (B2 and magnesium are required for absorption of B6), and in a yeast-free form for those sensitive to yeast or prone to abdominal bloating. Take plenty of water to aid absorption and prevent urine discoloration.

Vitamin B12

(Cobalamin)

Uses in the body: contributes towards healthy nervous and cardiovascular systems, the formation of red blood cells and bone marrow, production of genetic material and metabolism of fats, proteins and carbohydrates.

Signs of deficiency: exhaustion, anaemia, pallor, pins and needles in hands and feet, irritability, depression, shortness of breath on exertion.

Therapeutic uses: anaemia, fatigue, digestive problems, mental or nervous problems. Vegans and vegetarians can become deficient in B12 as it's mainly found in animal produce.

Dietary sources: meat (especially liver), fish, eggs, dairy produce, fortified cereals, brewer's yeast, yeast extract, blackstrap molasses, seaweed (it's present in blue-green algae such as spirulina and chlorella, but it may not be well absorbed by the body).

Cautions: the form hydroxycobalamin is preferable to cyanocobalamin, which can aggravate certain eye conditions. Check the labels. Toxicity is very rare.

Best taken: by injection for best absorption. Drops (taken with water or under the tongue) may be better absorbed than tablets. Take at breakfast with food.

Biotin

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.

Cautions: no contraindications, but keep to recommended dosage.

Best taken: with food at breakfast and lunch/dinner for split dose.

Vitamin C

(Ascorbic acid)

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.

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.

Vitamin D

(Cholecalciferol)

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.

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 600mg 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.

Vitamin E

(Tocopherol)

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.

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.

Folic acid

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.

Cautions: large intake (400 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.

Vitamin K

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.

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.