I've recently read that you can overdose on vitamins. What particular vitamins are most dangerous, and in what quantities? What is the prescribed dosage of vitamin C to be taken for colds?
Conventional response: Vitamins are complex substances needed by the body for various metabolic processes; they are vital for good health. Many of the body's chemical reactions can only take place in the presence of vitamins.
Basically, an excess of water-soluble vitamins will be eliminated from the body in urine. Fat-soluble vitamins - A,D,E and K - are potentially toxic if taken at high levels for a prolonged period, as the body can stockpile them in fat cells.
There can be confusion about the recommended daily allowances (RDAs) of vitamins. They are actually a minimum rather than a maximum recommended intake - the amount you should take in your diet to prevent disease. Maximum safe levels are usually a multiple of the RDA.
France and Germany have traditionally set upper limits based broadly on their RDAs; their influence on EU harmonisation was evident last week as the European Parliament reduced the free sale of vitamins containing high doses.
Vitamin C helps the body fight infection, speeds up wound healing, prevents bruising and helps the skin maintain its elasticity. The current EU RDA is 60 milligrams, although doses up to 2,000 milligrams are considered safe.
Dr Muiris Houston
Alternative response: Vitamins are divided broadly into two groups: fat soluble and water soluble. The B vitamins and vitamin C are water soluble, which means that the body can't store them, and simply excretes whatever isn't absorbed. Vitamins A, D and E are fat soluble and are stored by the liver. Long-term supplementation of these vitamins at high dosages is not advised, as in theory the body can reach toxic overload.
Any possible risk attaching to vitamin supplementation needs to be viewed relative to the risks attaching to other ingested substances. The risk is theoretical in the Irish context where we have no recorded cases of fatality due to vitamin overdose. In this country, dosage levels of vitamins is in many cases considerably lower than those available in the UK, and dramatically lower than those available in the US.
The sad fact is that many higher level, non-toxic vitamins which are used for maintaining and promoting health are to be removed from open sale as a result of the Food Supplements Directive which was passed by the European Parliament last week. This, in my opinion, will lead to further erosion of consumers' freedom to choose safe and effective remedies.
Everbody's requirement for vitamin C is different. However, to ward off colds the general dosage recommended is 1,000 milligrams per day, increasing to twice or three times this dosage a day when the bug hits, perhaps combining this with the herb echinacea, which will help in building a strong immune system.
Erica Murray
Erica Murray is co-owner of the Hopsack Health Store, Rathmines, Dublin and a member of the Irish Association of Health Stores. The IAHS can be contacted on tel: 0903 29981
The advice in this column is not intended as a substitute for advice received directly from a medical doctor or alternative practitioner. You should receive a thorough diagnosis before embarking on treatment