Vitamins and Cancer

A randomized placebo-controlled trial in 14,641 male physicians > 50 years old followed for a median of 11.2 years, which was recently published online in JAMA (October 17, 2012), found that cancer occurred in 1290 men taking a multivitamin supplement (Centrum Silver) and in 1379 men taking an identical-looking placebo. This difference was statistically significant (p=.04). There was no statistically significant effect on any particular cancer. Adherence and reporting were unusually complete for such a long-term study, presumably because it was conducted in physicians. The results could have occurred by chance (4 chances out of 100), but the study certainly looks tight.

Nevertheless, even though I am a well-nourished US male physician >50 years old, I don’t plan to race out to the nearest CVS to stock up on Centrum Silver while the supplies last.  For one thing, the Centrum Silver product study participants took early in the study is not the same product offered under the same name today. It now has more vitamin D, less beta carotene, and lutein and lycopene have been added. I don’t know anything about the efficacy and safety of lutein and lycopene, but I am a strong believer in the adage that any substance that has biological activity can have unwanted effects.

Which brings me to beta carotene. The last time The Medical Letter wrote about vitamin supplements (December 12, 2011), we pointed out that 2 well conducted, placebo-controlled studies, published in The New England Journal of Medicine, in Finnish smokers, former smokers, and workers exposed to asbestos found that those who took a beta-carotene supplement had a significantly increased risk of developing lung cancer. As a former smoker, that closes the book on beta carotene for me.

And what about the other half of the human race? Our 2011 article also mentioned that a study, published in the Archives of Internal Medicine, in 38,772 women (mean age 61.6 years) found that self-reported use of at least one supplement containing either multivitamins, vitamin B6, folic acid, iron, magnesium, zinc or copper was associated with an increased mortality rate.

So I guess if you’re not a well-nourished US male physician > 50 years old who never smoked and has a supply of the old formulation of Centrum Silver, I’d give it a pass. But you won’t have any trouble finding people who think otherwise.

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  1. Reid Gliddon, BS-Phm, MS says:

    From what I’ve read, it’s the alpha-tocopherols that can maybe promote the development of prostate cancer but not the mixed version of delta, gamma, and beta tocopherols. Even when mixed with alpha-, the mixed formulations do not result in higher cancer incidences, whereas the alpha- alone does. These results seem to be overlooked in the conventional medical press.

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