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Antioxidant supplements - Health promoters or maybe even lethal?
(February 2005)

Antioxidants have been touted as doing a lot of wonderful things - preventing heart attacks, strokes, cancer, even aging. The antioxidants that have been studied most are vitamins A, C, E, beta carotene, and, to a lesser extent, selenium. In the October 2, 2004 issue of The Lancet is an analysis of multiple trials of one or more of these five antioxidants (a meta-analysis) in regard to cancers of the stomach, esophagus, large bowel, pancreas, and liver. This technique combines large studies; as a result, it is easy to get very impressive statistical significance; in this meta-analysis, there were 170,525 individual participants.

The results were as follows:

- Vitamins A, E, C, and beta carotene alone or in any combination showed no protection against any of the gastrointestinal tract cancers studied. However, there were not enough trials of vitamin C alone to draw any conclusions about that vitamin.

- Selenium appeared to reduce the risk of liver cancer in three Chinese studies.

- There was a small increase in deaths from any cause that appeared to relate to administration of beta carotene.

Commentary: This study has been over interpreted. It has been said that premature death would occur in 9,000 of every one million persons taking antioxidant supplements. Any such conclusion would be nonsense. The dangers of beta carotene are largely based on studies of lung cancer in heavy smokers. Reasonable conclusions from this and other studies would be:

- Vitamins A, C, E, and beta carotene do not prevent intestinal or liver cancers.

- Selenium looks interesting in the prevention of liver and perhaps bowel cancers, but there are not nearly enough data and it is well to remember that there is a narrow range between potential beneficial effects of selenium and selenium toxicity. At present, selenium supplementation cannot be recommended for cancer prevention, but it is still under investigation, not only in regard to liver and bowel cancers, but also prostate cancer.

- There is no reason to give beta carotene to anyone in the hope of preventing cancer, heart disease, or stroke.

Rating: None needed

Bjelakovic, G., et al. Antioxidant supplements for prevention of gastrointestinal cancers. The Lancet. Vol 364 (October 2) Pgs 1219-1227. 2004.

This study must not be used to deter standard one-a-day multivitamin use or use of folic acid supplements. This study has nothing to do with such one-a-day use which is recommended by some experts.

- Pregnant women should receive a routine one-a-day vitamin supplement and all women who might get pregnant should either have a daily supplement containing a minimum of 400 micrograms of folic acid or be absolutely sure they get a lot of folic acid in the diet (a supplement is preferred because it guarantees adequate blood levels).

- Those over age 60 should certainly take a folic acid supplement (they often absorb less from the intestines), either alone or probably better as a one-a-day multi-vitamin supplement. The problem with most one-a-day multi-vitamins is that they contain too many components, some of which are not needed, some of which may interfere with each other.

- One argument for the one-a-day recommendation for adults is that the best way to keep homocysteine levels normal or low is to have a good intake of folic acid (probably 800 micrograms a day by diet and supplement). Vitamins B12 and B6 may add to folic acid’s effect on homocysteine levels. High homocysteine levels are a risk factor for cardiovascular and, perhaps, other diseases.

So, eat a good diet with plenty of fruits and vegetables; if under age 60, a one-a-day multivitamin is optional, but there is no reason not to take one; if over age 60, take a one-a-day multivitamin with an optional additional 400 micrograms of folic acid. Women who might get pregnant should be forewarned that they must have good levels of folic acid at the time of conception because, by the time the first period is missed, it is too late to intervene since the neurologic abnormalities that can be largely prevented by folic acid occur during the first four weeks of conception.

One of our Scientific Advisory Board feels the negative statement about beta carotene is too strong; he notes the whole area of potential beta carotene benefit is still unsettled and under investigation.

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