What is Selenium?
Selenium is a mineral that is found in relatively small amounts in the human body. As a potent antioxidant, selenium helps prevent cell and tissue damage from free radicals and is also involved in strengthening the immune system.
Selenium and the Risk of Prostate Cancer
Studies of large populations indicate that low levels of selenium in the diet are associated with an increased risk of prostate cancer and other forms of cancer. (PDR p. 418) This suggests that taking selenium supplements might help prevent prostate cancer. In the large-scale Selenium and Vitamin E Cancer Prevention Trial (SELECT Trial), however, the researchers found that selenium, either alone or combined with vitamin E, did not prevent the development of prostate cancer. The researchers did observe a statistically nonsignificant increased risk of prostate cancer with vitamin E alone and newly diagnosed type 2 diabetes with selenium alone. (Lippman 2009) A post-SELECT Trial analysis, however, has suggested that further research is needed to determine whether selenium should still be considered in the fight against prostate cancer. (Ledesma 2010)
In another 2009 study, investigators found that high levels of selenium in the bloodstream actually increased the risk of development of an aggressive form of prostate cancer in men who possessed a specific genetic variation (the “V” for the SOD2 gene). (Chan 2009)
One study has suggested that selenium may reduce the risk of prostate cancer. At the Arizona Cancer Center, researchers discovered that men who took 200 micrograms of selenium daily had a reduced risk of prostate, lung, and colorectal cancers as well as a reduced risk of death from these diseases. (Clark 1996)
Selenium and High-Grade Prostatic Intraepithelial Neoplasia
The impact of selenium on men with high-grade prostatic intraepithelial neoplasia (HGPIN) was the subject of a multicenter phase III trial presented at the American Urological Association Annual Meeting in 2010 in San Francisco. A total of 466 men with HGPIN were enrolled after they had a second negative repeat prostate biopsy, and they were randomly assigned to take either 200 mg daily of selenium or a placebo. After three years, 50 men who took selenium and 50 who took placebo had prostate cancer, leading the researchers to conclude that selenium does not prevent prostate cancer in men who have high-grade PIN. (Marshall 2010)
Scientists had hoped that selenium would prove to be helpful in the fight against prostate cancer. An article in a May 2009 Mayo Clinic Health Letter may say it all: “Selenium Supplementation Loses Favor.” However, selenium is still an important mineral for human health, and so it’s important to get at least the recommended 55 mcg (micrograms) daily for adults. Selenium is found in nuts (especially Brazil nuts), tuna, cod, turkey, beef, and plant foods. The amount of selenium in foods can vary widely because it depends on the level of selenium in the soil (for plants) and the foods eaten by mammals, fowl, and fish.
Chan JM et al. Plasma selenium, manganese superoxide dismutase, and intermediate- or high-risk prostate cancer. J Clin Oncol 2009 Aug 1:27(22): 3577-83
Clark LC et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. Nutritional Prevention of Cancer Study Group. JAMA 1996 Dec 25; 276(24): 1957-63
Ledesma MC et al. Selenium and vitamin E for prostate cancer: Post-SELECT status. Mol Med 2010 Sep 21
Lippman SM et al. Effect of Selenium and Vitamin E on Risk of Prostate Cancer and Other Cancers: The Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA 2009 Jan; 301(1):39-51.
Marshall JR. Presented at the American Urological Association Annual Meeting, May 29 to June 3, 2010, San Francisco.
PDR for Herbal Medicines, 3rd edition, Montvale, NJ: Thomson PDR., 2004, p. 418.