Confused by Which Vitamins to Take

QUESTION: Although I realize that vitamins are important things to have in a
good diet, I must admit that I am totally confused as to which ones I need,
and how much to take. One of my friends claims that you can't get enough
vitamins, and takes massive doses to prevent cancer. Can you bring any logic
to all of this disorder and help me chart a sane course?
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ANSWER: If history can help predict the future, this answer will provoke a
wide variety of mail, most of it telling me how little I really know, and
offering to write the column for me. And though I think I have already heard
it all, there will be new stories of how someone escaped sure death by
ignoring the advice of a traditional physician, and accepting the claims of a
modern day snake-oil merchant. Vitamins are truly remarkable chemicals when
used for a specific reason or purpose. They were originally discovered as the
needed component of a diet to cure a deficiency disease, an ailment actually
caused by the lack of sufficient vitamin. Scurvy in sailors on those romantic
old square riggers was over come by citric juice (limes, lemons and oranges)
for it was a fine source of Vitamin C. Incidentally that is how British
sailors and the all English became known as "limeys," as citric fruits were
made part of the marine diet to overcome the disease. Most of the vitamins
were discovered in like manner, as the needed substance in the diet to
overcome a deficiency disease. About 40% of the adult American population
uses vitamins and minerals on a daily basis, and with such a large population,
misuse may often occur. An RDA (or Recommended Daily Allowance) has been
established as "the levels of essential nutrients considered in the judgement
of the Committee on Dietary Allowances of the Food and Nutrition Board on the
basis of available scientific knowledge to be adequate to meet the known
nutritional needs of practically all healthy persons." They provide a solid
base for all needs, as we may then increase the amounts where specific
deficiency conditions exist, as in pregnancy, poor health, or poor nutrition.
Vitamins used in these cases are considered "therapeutic agents" rather than
"nutritional supplements". At present there is no vitamin which is
acknowledged as an agent that either cures or prevents cancer. Your
pharmacist or physician will be happy to indicate the proper quantity of
vitamins that fulfil your personal dietary needs.