Extra vitamin E linked to prostate cancer, but diet still merits study ...

UCSF researcher remains optimistic about identifying dietary, lifestyle interventions that prove beneficial to health.

June Chan, UC San Francisco

Taking vitamin E supplements appears to increase a man?s risk of prostate cancer, according to a study that appears in the Oct. 12 issue of the Journal of the American Medical Association.

A multi-institutional team of researchers reported findings from the Selenium and Vitamin E Cancer Prevention Trial (SELECT), a study begun in 2001. They found that men age 50 and older who took 400 units of vitamin E daily were diagnosed with prostate cancer at a 17 percent higher rate than men who popped placebos.

UCSF?s June Chan, Sc.D., is no stranger to studies of dietary supplements and cancer that turn out to be a bust, including studies of vitamin E.

Earlier, as a graduate student, Chan investigated vitamin E. Working with Harvard epidemiologist Walter Willet, she found no epidemiological evidence that vitamin E prevented prostate cancer in men generally. However, the researchers did see a trend toward fewer prostate cancers in smokers.

Chan remains optimistic about identifying dietary and lifestyle interventions that prove beneficial to health.

?Healthy eating habits, regular physical activity, not smoking, and avoiding overweight and obesity remain important tools for us to prevent several major chronic diseases,? she says.

Supplements, despite promising signs from earlier epidemiological studies, have fared poorly in controlled clinical trials, in which participants are randomly assigned to different treatment arms. These controlled clinical trials remain the gold standard by which to evaluate any health claims.

An early disappointing milestone in anti-oxidant supplement research was a 1994 study of vitamin E and beta-carotene as a means to lower lung cancer risks among smokers. Daily supplementation with 50 units of Vitamin E had no benefit, while beta-carotene was associated with an increased risk for lung cancer.

However, in that same clinical trial researchers observed that there were more than 30 percent fewer cases of prostate cancer and prostate cancer deaths among the men who took the vitamin E supplements. This association spurred interest in launching the SELECT trial, focused specifically on prostate cancer.

Although there were more cancers among men in SELECT who took supplements, it?s too soon to say whether Vitamin E or selenium supplementation will lead to more prostate cancer deaths among the study participants, Chan says. More cancers does not necessarily mean more deadly cancers.

?The majority of these cancers were earlier-stage disease detected by PSA screening. It is likely that a fair proportion of these are indolent tumors ? meaning cancers that would not cause morbidity or mortality if left undiagnosed.?

The study is another reminder that more is not always better, Chan says. ?Supplements are not the same as eating a healthy diet,? she adds.

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Source: http://health.universityofcalifornia.edu/2011/10/25/extra-vitamin-e-linked-to-prostate-cancer-but-diet-still-merits-study/

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