February 24, 2014
Vitamin E And Selenium Supplements Could Increase Risk Of Prostate Cancer
redOrbit Staff & Wire Reports - Your Universe Online
High-dose supplementation with both the trace element selenium and vitamin E can increase the risk of prostate cancer in some men, according to a new multi-center study appearing in Friday’s edition of the Journal of the National Cancer Institute.
The study, which was led by Dr. Alan Kristal of the Fred Hutchinson Cancer Research Center, found that vitamin E could heighten the risk in men with low baseline selenium levels, while selenium supplements can increase the prostate cancer risk in men who already have high baseline levels of the mineral, the institute explained in a statement.
Those findings are based on the results of the Selenium and Vitamin E Cancer Prevention Trial (SELECT), a randomized and placebo-controlled trial involving more than 35,000 male participants. It set out to determine if taking high-dose vitamin E (400 IU/day) or selenium (200 mcg/day) supplements could help prevent prostate cancer.
The trial began in 2001, and while it was scheduled to continue for a 12 year period, it was halted in 2008 because it uncovered no protective effect from selenium and a potential increased risk resulting from vitamin E use. Each of the participants were followed for an additional two years after they stopped taking the supplements, and it was discovered that men who used vitamin E had a statistically significant 17 percent increased prostate cancer risk.
Based on the potential increased prostate cancer risk and the lack of evidence to suggest that either supplement can help prevent other severe health conditions in the US and Canada, the study authors suggest that men over the age of 55 “should avoid selenium or vitamin E supplementation at doses that exceed recommended dietary intakes.”
“Many people think that dietary supplements are helpful or at the least innocuous. This is not true,” Dr. Kristal explained in a statement Friday. “We know from several other studies that some high-dose dietary supplements… increase cancer risk. We knew this based on randomized, controlled, double-blinded studies for folate and beta carotene, and now we know it for vitamin E and selenium.”
“Men using these supplements should stop, period,” he added. “Neither selenium nor vitamin E supplementation confers any known benefits – only risks. While there appear to be no risks from taking a standard multivitamin, the effects of high-dose single supplements are unpredictable, complex and often harmful… There are optimal levels, and these are often the levels obtained from a healthful diet, but either below or above the levels there are risks.”
The research was funded by the National Cancer Institute, and in addition to the Fred Hutchinson Cancer Research Center, investigators from the University of Missouri, the University of Texas, the University of California Irvine, the National Cancer Institute, the University of California San Diego and the Cleveland Clinic took part in the study.