Selenium, a trace mineral found in grains, nuts and meats, and vitamin E - whether taken alone or in combination - do not prevent prostate cancer, according to a new study.
The team led by scientists at The University of Texas M. D. Anderson Cancer Centre and Cleveland Clinic has shown that selenium and vitamin E showed no benefits for prostate cancer patients.
The study followed 35,533 participants from 427 sites in the United States, Canada and Puerto Rico.
The researchers conducted randomized, placebo-controlled and double blind trials.
The participants were divided into four intervention groups: selenium, vitamin E, both selenium and vitamin E, and placebos.
The study found no evidence of benefit from selenium, vitamin E, or both.
However, the data showed two statistically non-significant findings of concern: slightly increased risks of prostate cancer in the vitamin E group and type two diabetes mellitus in the selenium group. Both trends may be due to chance and were not observed in the group taking selenium and vitamin E together.
"Although supplementation has been discontinued, we will continue to follow these men and monitor their health for approximately three more years, conducting regular prostate screening tests and questioning them about diabetes and other health issues," said Scott M. Lippman, M.D., professor and chair of Thoracic/Head and Neck Medical Oncology at M. D. Anderson.
"Doing so is critical not only to determine any possible long-term effects of the selenium and vitamin E, but also in order to gain a better understanding of prostate and other cancers and age-related disease," he added.
The study is published in the Journal of the American Medical Association (JAMA).