Supplement Risk Exposed by SELECT

Selenium, Vitamin E May Increase Risk for Prostate Cancer

Gerald Chodak, MD


March 03, 2014

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Hello. I am Dr. Gerald Chodak for Medscape. This week I want to talk about the impact of vitamin E and selenium on the development of prostate cancer.

The SELECT trial[1] was begun in 2001. In this trial, 35,000 men over the age of 50 years were randomly assigned to receive either selenium plus placebo, vitamin E plus placebo, selenium plus vitamin E, or placebo alone. The results were reported in 2008 and showed no reduction in the development of prostate cancer.

Now, another study[2] has updated that initial analysis. The original investigators had measured the amount of selenium in toenails of the men in the trial, and that data was stored. This analysis included an examination of whether that baseline selenium level had any impact on the development of prostate cancer.

The authors found that those men who had received no supplementation had no change in the development of prostate cancer over time. However, those men who were taking selenium and who had a high level of selenium to begin with had a significant, nearly 2-fold increase in the development of high-risk prostate cancer. Those men taking vitamin E, even those with a low level of selenium in their toenails, had a significant increase in the risk of developing any prostate cancer and high Gleason score prostate cancer.

This new, further analysis has several important messages. It demonstrates to the public that in the absence of prospective randomized trials, it is difficult to make any conclusions about the impact of taking vitamins, herbs, or supplements. This randomized study demonstrates that not only was there no benefit, but there was actually harm resulting from taking vitamin E and selenium, in terms of the development of prostate cancer.

This is an important message, and it raises questions about other vitamins, herbs, and supplements that patients may take in the hope of improving their health, when in reality the opposite might occur. Patients, and men in general, should not assume that there is no risk from taking these supplements, as clearly demonstrated in this trial.

At the end of the day, this is an important study and an important analysis demonstrating that not only do vitamin E and selenium not help prevent prostate cancer, as uncontrolled studies suggested, but in fact they raise a man's risk of getting a serious cancer.

I look forward to your comments. Thank you.


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