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Vitamins and minerals - what do they do?

Reviewed by Dr Dan Rutherford, GP

Recommended daily amounts (RDAs)

Micro vs milli

Check the letters after the RDA carefully.

One microgram (mcg or µg) is a thousand times smaller than a milligram (mg).

Throughout this factsheet the recommended daily amount (RDA) refers to the EU guidance that is used for nutrition tables on food products.

Nutritional requirements are often slightly different for young children, adolescents, and during pregnancy and breastfeeding.

Ask your doctor or pharmacist if you are concerned about your vitamin intake.

Vitamins

Vitamin A (retinol) properties
Good for	Signs of deficiency	RDA	Good sources	Poisoning	Destroyed by
Eyesight, growth, appetite and taste.	Night-blindness.	800 micrograms	Liver, fish-liver oil, carrots, green leafy vegetables, egg yolks, enriched margarine, milk products, yellow fruits.	This vitamin is fat-soluble and so is stored in the body for a long time, especially in pregnancy. An overdose may be dangerous.	Fatty acids.

Vitamin B1 (thiamine) properties
Good for	Signs of deficiency	RDA	Good sources	Poisoning	Destroyed by
Nervous system, digestion, muscles, heart, alcohol-damaged nerve tissues.	Tingling in fingers and toes, confusion, difficulties in maintaining balance, loss of appetite, exhaustion, weakened powers of concentration.	1.4mg	Liver, yeast, rice, wholemeal products, peanuts, pork, milk.	No danger. It dissolves in water, so any excess is passed in urine.	High temperatures, alcohol and coffee.

Vitamin B2 (riboflavin) properties
Good for	Signs of deficiency	RDA	Good sources	Poisoning	Destroyed by
Growth, skin, nails, hair, sensitive lips and tongue, eyesight, the breakdown of protein, fat and carbohydrate.	Itchy irritated eyes, itchy mucous membranes (nose/mouth/throat), itchy lips and skin.	1.6mg	Milk, liver, yeast, cheese, green leafy vegetables, fish.	No danger. It dissolves in water, so any excess is passed in urine.	Alcohol and light (this is why milk-cartons are better than bottles).

Vitamin B6 (pyridoxine) properties
Good for	Signs of deficiency	RDA	Good sources	Poisoning	Destroyed by
Preventing skin conditions, nerve problems, helps the body absorb protein and carbohydrate.	Skin inflammation.	2mg - women taking the contraceptive pill may need more.	Fish, bananas, chicken, pork, wholegrains, dried beans.	May cause nerve problems in large doses. Evidence is conflicting about the maximum safe dose, so get medical advice before exceeding the RDA.	The contraceptive pill, roasted or boiled food, alcohol and oestrogen (the female hormone).

Vitamin B12 (cobalamin) properties
Good for	Signs of deficiency	RDA	Good sources	Poisoning	Destroyed by
Making red blood and the formation of the nerves.	Tiredness, breathing difficulties, dizziness, abnormalities in nerve tissue function.	1 microgram	Fish, liver, beef, pork, milk, cheese.	No danger. It dissolves in water, so any excess is passed in urine.	Water, sunlight, alcohol, oestrogen and sleeping pills

Vitamin C (ascorbic acid) properties
Good for	Signs of deficiency	RDA	Good sources	Poisoning	Destroyed by
Immune defence system, protection from viruses and bacteria, healing wounds, reducing cholesterol, cell lifespan, preventing scurvy. It's also a natural laxative.	Tiredness, bleeding gums, slow-healing wounds.	60mg	Citrus fruits, kiwi fruit, berries, tomatoes, cauliflower, potatoes, green leafy vegetables, peppers.	Large doses can cause diarrhoea and nausea. Some scientists have argued that 1000-5000mg per day may damage your DNA.	Boiling food, light, smoking and heat.

Vitamin D properties
Good for	Signs of deficiency	RDA	Good sources	Poisoning	Destroyed by
Strong bones and teeth	Unhealthy teeth, osteomalacia (causes weakening of bones), rickets in children.	5 micrograms	Sunlight (the action of sunlight on the skin allows our bodies to manufacture vitamin D), cod-liver oil, sardines, herring, salmon, tuna, milk and milk products.	This vitamin is fat-soluble so can accumulate in the body. Overdoses are dangerous.	Mineral oil.

Vitamin E (tocopherol) properties
Good for	Signs of deficiency	RDA	Good sources	Poisoning	Destroyed by
Fighting toxins - vitamin E is a powerful antioxidant.	Weak muscles and fertility problems.	10mg	Nuts, soya beans, vegetable oil, broccoli, sprouts, spinach, wholemeal products, eggs.	There is a slight risk of overdose, because vitamin E is fat soluble.	Heat, oxygen, frost, iron, chlorine and mineral oil.

Folic acid properties
Good for	Signs of deficiency	RDA	Good sources	Poisoning	Destroyed by
Production of red blood cells. It is essential in the first three months of pregnancy to prevent birth defects such as spina bifida, cleft palate or cleft lip.	Tiredness due to anaemia, red tongue.	200 micrograms. Women planning to conceive should take a daily supplement of 400mcg, continued for the first 12 weeks of pregnancy.	Carrots, yeast, liver, egg, yolks, melon, apricots, pumpkin, avocado, beans, rye and wholewheat, green leafy vegetables.	No danger. It dissolves in water, so any excess is passed in urine.	Water, sunlight, oestrogen, heat.

Minerals

Calcium
Good for	Signs of deficiency	RDA	Good sources	Poisoning
Strong bones and teeth, nerve function, muscle contraction, blood clotting.	Poor teeth and brittle bones.	800mg	Milk, cheese, butter, yoghurt and green leafy vegetables.	High doses can lead to headaches, stomach pain, high blood pressure and diarrhoea. Excess calcium can be deposited as kidney and gall bladder stones.

Iron
Good for	Signs of deficiency	RDA	Good sources	Poisoning
Red blood cells and muscle function, white blood cells and the immune system.	Tiredness, irritability, difficulties concentrating.	14mg	Lean red meat, oily fish, egg yolks, green leafy vegetables, nuts, wholegrains and wholewheat.	Iron is stored in the body and high doses (over 17mg) can lead to constipation, vomiting, nausea and diarrhoea. Very high doses can be fatal.

Magnesium
Good for	Signs of deficiency	RDA	Good sources	Poisoning
Converting energy from food, cell repair, building strong bones, teeth and muscles, regulating body temperature.	Muscle spasms, and has been associated with heart disease, diabetes, high blood pressure and weak bones.	300mg	Green leafy vegetables, wholegrains and nuts.	High doses can cause diarrhoea.

Zinc
Good for	Signs of deficiency	RDA	Good sources	Poisoning
Immune system, the breakdown of protein, fat and carbohydrate.	Lesions on skin, eyes and in throat, loss of taste and smell, hair loss, diarrhoea, slow healing of wounds, growth problems in children.	15mg	Meat, shellfish, milk brown rice and wholegrains.	High doses can lead to stomach cramps, nausea and vomiting.