Ever since the urging of Nobel winner Linus Pauling on the benefits of
megadosing on vitamin C, the medical community has been debating the right
dose of this vitamin. Although many doctors stood firm for a long time
asserting that the amounts recommended by the RDA were adequate, more and more
doctors are now realizing that higher dosages can confer additional
antioxidant benefits. However, the "ideal dose" of vitamin C has not yet been
determined, nor is it likely to be determined soon. Nevertheless, we now
suspect that excessive dosages of vitamin C, except perhaps in the therapy of a particular medical condition, may not be necessary to take on a regular
basis.
A study published in the American Journal of Clinical Nutrition
(66:1165-1171, 1997) points that large doses of ingested vitamin C may be
excreted without being utilized. When the dosage of vitamin C given to a group
of healthy men was increased from 200 mg a day to 2,500 mg a day, the serum
levels increased only negligibly, from 12 mg/dl to 15 mg/dl. James Blanchard,
Ph.D., a professor of pharmacological sciences at the University of Arizona in
Tucson, reports that the blood levels of vitamin C generally reflect the
tissue levels.
Comments:
Over the past few years I have recommended to my patients that they
really do not need to take vitamin C supplements in dosages greater that 250
mg twice a day. This study adds an additional note of certainty to my opinion
that a maximum dosage of 500, or perhaps even up to 1,000 mg a day may be all
that's needed. This amount, of course, is for those who have no medical
problems and are just supplementing with vitamin C for preventive reasons. It
is possible that those with chronic medical conditions, or the elderly, may
need more of this vitamin.
Again, moderation seems to be the key in vitamin supplementation. Obviously
the RDA of 60 mg a day is probably not optimal, then again, megadoses greater
that 1,000 mg a day, may also be unnecessary.
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