Vitamins - what do they do?

Reviewed by Dr Dan Rutherford, GP
Recommended daily amounts (RDAs)Throughout this factsheet, recommended daily amount refers to the European Union recommended daily amounts (EU/RDA) for nutritional labelling of food products. Nutritional requirements are often slightly different for young children and adolescents, and during pregnancy and breastfeeding. Ask your doctor or pharmacist if you are concerned about your own or your children's vitamin intake.
Vitamin A (retinol) propertiesGood for:
eyesight
growth
appetite and taste.Signs of vitamin A deficiency:
night-blindness.Good sources of vitamin A:
liver
fish-liver oil
carrots
green leafy vegetables
egg yolks
enriched margarine
milk products
yellow fruits.Recommended daily amount: 800 micrograms.
Poisoning: vitamin A is a fat-soluble vitamin and so it is stored for a long time in the human body, especially in pregnancy. An overdose may be dangerous. Destroyed by: fatty acids.
Vitamin B1 (thiamine) properties Good for:
nervous system
digestion
muscles
the heart
alcohol-damaged nervous tissues.Signs of vitamin B1 deficiency:
tingling in fingers and toes
confusion
difficulties in maintaining balance
loss of appetite
exhaustion
weakened powers of concentration. Good sources of vitamin B1:
liver
yeast
rice
wholemeal products
peanuts
pork
milk.Recommended daily amount: 1.4mg.Poisoning: no poisoning dangers as the vitamin dissolves in water, so excess is excreted in the urine. Destroyed by: high temperatures, alcohol and coffee.
Vitamin B2 (riboflavin) properties Good for:
growth
skin
nails
hair
sensitive lips and tongue
eyesight
protein, fat and carbohydrate breakdown. Signs of vitamin B2 deficiency:
itching and irritation of the eyes
itching mucous membranes
itching lips and skin. Good sources of vitamin B2:
milk
liver
yeast
cheese
green leafy vegetables
fish.Recommended daily amount: 1.6mg.Poisoning: no danger of poisoning as the vitamin dissolves in water, so excess is excreted in the urine.Destroyed by: light (this is why milk-cartons are better than bottles) and alcohol.
Vitamin B6 (pyridoxine) properties Good for:
preventing skin conditions
nerve problems
helping the body absorb proteins and carbohydrates.Signs of vitamin B6 deficiency: skin inflammation.Good sources of vitamin B6:
fish
bananas
chicken
pork
whole grains
dried beans.Recommended daily amount: 2mg. Women taking the contraceptive pill may need more. Poisoning: may cause nerve problems in large doses, but current evidence is conflicting about the maximum safe dose. Discuss this with your pharmacist if you are concerned. Destroyed by: the contraceptive pill, roasted or boiled food, alcohol and oestrogen (the female hormone).
Vitamin B12 (cobalamin) properties Good for:
making red blood cells
the formation of the nerves. Signs of vitamin B12 deficiency:
tiredness due to anaemia
abnormalities of nervous tissue function.Good sources of vitamin B12:
fish
liver
beef
pork
milk
cheese. Vitamin B12 deficiency can arise in strict vegans because our dietary sources of vitamin B12 are animal in origin. The other main cause of vitamin B12 deficiency is pernicious anaemia.Recommended daily amount: 1 microgram. Poisoning: no danger as the vitamin dissolves in water, so excess is excreted in the urine. Destroyed by: water, sunlight, alcohol, oestrogen and sleeping pills.
Vitamin C (ascorbic acid) properties Good for:
the immune defence system
protection from viruses and bacteria
healing wounds
reducing cholesterol content of the blood
a natural laxative
cell lifespan
preventing scurvy. Signs of vitamin C deficiency:
tiredness
bleeding gums
slow-healing wounds. Good sources of vitamin C:
citrus fruits - especially kiwi fruit
berries
tomatoes
cauliflower
potatoes
green leafy vegetables
peppers.Recommended daily amount: 60mg. Poisoning: Large doses can cause diarrhoea and nausea. Some scientists have recently argued that 1 to 5g per day may influence your genes. Destroyed by: boiling food, light, smoking and heat.
Vitamin D propertiesGood for:
strong bones and teeth.Signs of vitamin D deficiency:
unhealthy teeth
osteomalacia (causes weakening of bones)
rickets in children.Good sources of vitamin D:
cod-liver oil
sardines
herring
salmon
tuna
milk and milk products
sunlight (the action of sunlight on the skin allows our bodies to manufacture vitamin D).Recommended daily amount: 5 micrograms.Poisoning: this vitamin is fat-soluble so can accumulate in the body and overdoses are dangerous. Destroyed by: mineral oil.
Vitamin E (tocopherol) properties Good for:
fighting poisons - vitamin E is a powerful 'anti-oxidant'.Signs of vitamin E deficiency:
weak muscles
fertility problems. Good sources of vitamin E:
nuts
soya beans
vegetable oil
broccoli
sprouts
spinach
wholemeal products
eggs.Recommended daily dose: 10mgPoisoning: there is a theoretical but slight risk of overdose, as vitamin E is fat soluble. Destroyed by: heat, oxygen, frost, iron, chlorine and mineral oil.
Folic acid properties Good for:
production of red blood cells
essential during the first three months of pregnancy to prevent birth defects such as spina bifida, cleft palate or cleft lip. Signs of folic acid deficiency: anaemia, red tongue.Good sources of folic acid:
carrots
yeast
liver
egg yolks
melon
apricots
pumpkin
avocado
beans
rye and whole wheat
green leafy vegetables.Recommended daily amount: 200 micrograms. Pregnant women and women planning a pregnancy should take a daily supplement of 400 micrograms, continued for the first 12 weeks of pregnancy.Poisoning: no danger of poisoning as it dissolves in water, so excess is excreted in the urine.Destroyed by: water, sunlight, oestrogen, heat.
Based on a text by Dr Carl J Brandt