In findings recently published by the Fred Hutchinson Cancer Research Center, a significant increase in the risk of prostate cancer is associated with intake of high-dose dietary supplements containing vitamin E and selenium. This shed light on a new consideration in the prevention of a disease which already claims the lives of thousands of men in the U.S. every year.

Dr. Alan Kristal, first author of the study, said the finding also reminds the public of the general risks involved with taking any high-dose dietary supplements. Many people assume that these are simple compliments to a regular diet and “are helpful or at the least innocuous.” But this is not true as he goes on to explain, “We know from several other studies that [these supplements] provide far more than daily recommended intakes of micronutrients” and increase cancer risk. He added that these results are based on randomized, double-bind studies with controls which have tested for the effects of folate and beta carotene and now also for vitamin # and for selenium.

The work analyzed data gathered during a large-scale survey – the Selenium and Vitamin E Cancer Prevention Trial (SELECT) — which was designed to determine if high doses of vitamin E or selenium would help reduce prostate cancer risks.

The study began in 2001 and was scheduled to be conducted over a 12 year period ending in 2013, but was brought to an end in 2008 as no defensive effect from selenium was found but clear indications that vitamin E actually increase the risk of cancer became apparent. Kristal and his team established, two years after ending the survey, that patients who had received a high daily dose of vitamin E had a 17 percent higher chance of contracting prostate cancer.

The levels of selenium in trial participants played a significant role in the effects which supplemental selenium and vitamin E had on their resulting risk profiles.

Those who entered the trial with selenium baselines considered low nearly doubled their risk of aggressive cancer, a 91 percent increase, if they received a high daily dose of supplemental selenium. Those who entered the trial with high selenium levels soon experience toxic level of selenium after receiving high-dose supplements on a daily basis.

Those who had a relatively low baseline level of selenium and received vitamin E supplements increase their risk of prostate cancer by 63 percent and their risk of high-grade cancer by 111 percent, more than double, but participants starting with high selenium levels were apparently protected from the risk increasing effects of the vitamin E supplements.

Kristal explained to reporters that supplements of this type, especially vitamin E are very popular, but no proper study has demonstrated any efficacy towards the end of preventing major chronic diseases. Kristal added simply than men using these supplements should stop. Neither selenium, he intoned, nor vitamin E supplement regimens bestow any known benefits on those consuming them — only increased risk.

Men can, however, stick to their existing daily multivitamin routines without anxiety. Dr. Durado Brooks at the American Cancer Society remarks that the levels the test subjects were getting in the research study were much higher than anything found in typical multivitamins and higher than any daily recommended allowance. He went on to say that the effects of high-dose supplements of individual nutritive components are complex, unpredictable and demonstrably dangerous.

While new screening methods to help speed detection of prostate cancer have recently been announced, men would still do well to stop any supplemental intake of selenium and vitamin E to reduce the risk of contracting the deadly cancer in the first place.

By Brian Ryer

Sources:

Philly.com

CBC News

Science Codex

Medical Daily

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