In reply to owena:
> on the topic of vitamins etc, I sometimes take some multivitamins as few days before and after a strenuous event e.g. half marathon, welsh 3000s, etc just to make sure my body has everything it needs, but regularly taking vitamins reduces your bodies ability to absorb those vitamins from foods so in effect making you slightly dependent on them. I dont think its much of a risk to take them occasionally though as most are excretable via the kidneys e.g vitamin C / ascorbic acid. Some like vitamin A can be dangerous in very high levels e.g. eating a lions liver (as you do)
There are two big questions around vitamins pills (questions which overlap).
The first is to do with the bioavailability of vitamins in pill form. Just adding a vitamin to a food or pill does not guarantee that your body can absorb that vitamin (and not in the amount anticipated). Various nutrients and dietary components interfere with the bioavailability of vitamins. Thus the requirements for vitamins cannot be considered independently, and must be evaluated in relationship to other nutrients and compounds consumed by an individual.
This leads to the second question which is to do with how nutritionally complete a diet is. Supplementing with vitamins is a journey in to 'nutritionism' and this carries several assumptions; that we already know all the important nutrients and their functions, that the function of an isolated nutrient (even in a synthetic form not occurring in nature, e.g. folic acid) is exactly the same as its function in food, and that there are no competitive or synergistic effects between the thousands of chemical compounds found in one bite of real food.
Eat real food.