High dose selenium and vitamin E supplementation may increase the risk of prostate cancer in men, according to a new study.
Selenium (Se) is an essential trace mineral that is found in soil, water and some foods. The role of selenium in cancer prevention has been the subject of study and debate. In 2008, the government halted a major study, the Selenium and Vitamin E Cancer Prevention Trial (SELECT) study, which tested whether vitamin E and selenium, either taken alone or together, may help prevent prostate cancer. An early review of the data showed that the supplements were ineffective and may possibly lead to health risks.
In the new study, researchers analyzed data from the SELECT study to assess the effects of selenium and vitamin E supplementation in men based on their nutrient levels before supplementation was initiated.
The researchers found that selenium supplementation, both alone and combined with vitamin E, did not affect prostate cancer risk in men who had low selenium levels before supplementation. However, selenium supplementation significantly increased the risk of prostate cancer by 91% in men who had higher selenium levels before supplementation was initiated. Vitamin E supplementation did not affect prostate cancer risk in men with higher selenium levels, but did increase its risk in men with lower selenium levels at the beginning of the study.
The authors concluded that selenium supplementation did not reduce the risk of prostate cancer in men with low selenium levels, and increased its risk in those with high levels; therefore, selenium supplementation may provide no benefit in regards to prostate cancer risk and should be avoided at levels above daily recommendations. Similarly, vitamin E should not be taken in levels above recommended daily intakes. Further research is warranted.
For more information about selenium or vitamin E, please visit Natural Standard's Foods, Herbs & Supplements Database.