Selenium is an important trace mineral necessary for liver, heart, and proper immune system function. (1,2) Recommended daily intake for selenium in adults is 55 mcg per day.(1) Recently, it has become of great interest due to its “curative” effects in the treatment of prostate cancer.(3,4) Nonetheless, as with any given therapy, there is a limit in which the risks outweigh the expected benefits. This is true for selenium, as previous studies still remain inconclusive about the benefits of this essential trace mineral.
In this recent study, a panel of experts set out to find the beneficial range in which selenium significantly reduces the risk of developing prostate cancer. They performed a meta-analysis (a review of various studies) dealing with selenium status and prostate cancer, to determine how selenium levels in the blood and toenail are related to development of prostate cancer. They also wanted to discover, through the current research available, the optimum range of selenium intake that would be most beneficial in combating the disease.
In order to do this, researchers performed a systematic review of studies that were related to selenium and prostate cancer and designed to be either a case-control study, nested case control study, prospective cohort study, or randomized controlled trial. Twelve studies were selected. Together, these studies had a total of 13,254 participants and 5007 cases of prostate cancer. Nine out of 12, related plasma/serum selenium to prostate cancer and 3 studies related toenail selenium to prostate cancer.
Researchers extracted data from these studies in order to graphically determine the best explanation of the relation between selenium dosage and the risk of prostate cancer. What they found was that by increasing selenium status, you can decrease the risk of prostate cancer. However, the beneficial affect is limited to a specific range of selenium both in plasma/serum and in the toenail. In plasma, the optimal range of selenium that significantly lowers the risk of prostate cancer is 60 to 170ng/ml. Outside of this range, the risk for developing prostate cancer increases. In the toenail as well, prostate cancer risk decreased by roughly 30% with toenail selenium ranging from 0.85 to 0.94ng/g. (5)
As with all studies dealing with selenium and prostate cancer, researchers found that this relationship is not true for all cases. Other studies have demonstrated that selenium supplementation ranging from 200-400mcg in a selenium-deficient population did not decrease the risk of prostate cancer. Other studies in individuals with prostate cancer demonstrated positive treatment effects of selenium supplementation. (3-5)
All in all, we’ve come a long in understanding the effects of selenium in the treatment of prostate cancer. And although its full effects remain unclear, what is certain is that more studies are needed to establish a clear relationship between selenium status, selenium supplementation, and the risk of prostate cancer.
Chrystal Moulton, BS, graduated from the University of Illinois at Chicago, where she received her degree in Psychology with a focus on pre-medical studies. She is currently employed at NOW Foods as a Research Assistant in the Science Department. She currently resides in Schaumburg, IL.
- Burk RF, Levander OA. Chapter 16: Selenium. Modern Nutrition in Health and Disease. Shils ME. Lippincott Williams & Wilkins, 2006.
- Tapiero H, Townsend DM, Tew KD. The antioxidant role of selenium and seleno-compounds. Biomed Pharmacother. 2003 May-Jun;57(3-4):134-44.
- Richman EL, Chan JM. Selenium and prostate cancer: the puzzle isn’t finished yet. Am J Clin Nutr 2012;96:1-2.
- Fair WR, Fleshner NE, Heston W. Cancer of the prostate: a nutritional disease? Urology. 1997 Dec;50(6):840-8.
- Hurst R, Hooper L, Norat T, et al. Selenium and prostate cancer: systematic review and meta-analysis. Am J Clin Nutr. 2012 Jul;96(1):111-22. Epub 2012 May 30.