Written by Catherine Saxelby
on Monday, 16 March 2009.
Tagged: guides, healthy eating, healthy lifestyle, nutrition, vitamins
Vitamins are a group of organic compounds needed in minute quantities (less than 1 per cent of our food is composed of vitamins). There are thirteen known vitamins essential for health and growth, and nine of them are grouped together as the B group or 'B-complex' vitamins. These are thiamin (vitamin B1), riboflavin (B2), niacin, pyridoxine (B6), cyanocobalamin (B12), folate, biotin, pantothenic acid and a recent addition choline. Not all carry the number designation as some were discovered and numbered then later found to be other compounds - not vitamins.
Vitamins are usually classified as fat-soluble or water-soluble:
Vitamins regulate the body's metabolism, by speeding up chemical reactions, acting as antioxidants or forming an integral part of the structure of proteins, hormones and blood. The body cannot produce them so they must be supplied by food.
Vitamins are needed in minute amounts for health, growth and to prevent vitamin-deficiency diseases such as:
Ideally, it is best to obtain all your vitamins from food, not pills. Food provides vitamins in the most biologically-available form, in the right amounts and combined with other complementary nutrients. Except under special circumstances, from food there is low risk of overdose.
Vitamins work best together. Too much of one can disturb the balance of others. Vitamin C increases the absorption of iron; vitamin E acts together with selenium and vitamin C as anti-oxidants; folate supplements can mask the symptoms of B12 deficiency.
Vitamin deficiencies do not appear immediately even on a totally depleted diet. For example, our livers store enough vitamin B12 to last three to five years; vitamin C reserves can last for thirty days.
In recent years, however, attitudes to supplements have changed, as numerous studies have emerged suggesting that supplements, especially the antioxidant supplements, are associated with better health outcomes .
While there are certain groups who could benefit from a supplement (such as smokers, fussy eaters or the elderly), be wary of the over-enthusiastic promises made by vitamin sellers. Often the scientific evidence is not reliable, consisting of anecdotes from 'satisfied' patients or the people treating them.
Not all the claims for supplements have been proven. An often-quoted examination of studies into vitamin C and the common cold showed that it could slightly shorten the duration of colds - but not prevent them entirely.
If you do take supplements, think of them only as a ‘top up' to your daily diet. Supplements aren't ‘magic bullets' - they won't supply everything we get from good food (as many beneficial phyto-chemicals are not found in any pill) nor can they counteract a bad diet with too much fat or salt.
Often they leave you with a false sense of security so that you think you don't need to worry about the junk you've eaten.
For some vitamins, there's the possibility of overdose. There are potential dangers from excess doses of vitamins. Examples:
mg | stands for milligrams |
ug | stands for micrograms. 1000 micrograms (ug) = 1 milligram (mg) |
IU | stands for International Units. These units are a measure of the biological activity of a vitamin and were used before vitamins were available in pure form. You'll often read IU on the labels of supplements. |
References used
In the accompanying articles on individual vitamins in the Foodwatch website, you'll see figures for the recommended day's intake.
© Catherine Saxelby
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