Vitamins and Cancer Risk

May 10, 2015

By Steven Novella

One of the greatest triumphs of marketing over evidence was the incredible rise of vitamin supplement use in the 20th century. Supplement makers successfully created a “health halo” around vitamins, and taking your vitamins became a virtue, something mothers told their children to do. The evidence, however, does not tell such a simple story.

In recent years it has become increasingly apparent that there are unintended consequences to taking vitamin supplements, and in fact there may be a net negative health effect. This is especially true for those who are healthy and don’t need vitamins, and for those who exceed the recommend dosages.

A recent review of the last 20 years of literature on the subject, presented at theAmerican Association for Cancer Research 2015 meeting, found an overall increased risk of cancer among vitamin users. Dr. Tim Byers presented the study, which echoes the result of a 2012 review that he and others published. He specifically refers to two famous studies showing an increased risk of cancer from vitamins.

The 2011 SELECT trial found an overall increased risk of prostate cancer among men taking vitamin E.

It has also been shown, first in a 1994 NEJM study, that high doses of beta carotene increase the risk of lung cancer in smokers and those exposed to asbestos.

In fact, antioxidants in general lack evidence for an overall health benefit and in high doses may increase cancer and overall mortality.


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