Does Selenium Ward off Prostate Cancer?
Men with a high intake of the mineral selenium have a reduced risk of developing prostate cancer, according to a study published in the December issue of the Journal of Urology.1
The new study compared 52 men who had prostate cancer with 96 men of similar age without evidence of prostate disease. For each, blood samples from roughly four years prior to the study (and before development of prostate cancer) were analyzed for selenium concentration.
The men with the lowest blood levels of selenium were found to be four to five times as likely to develop prostate cancer over the next four years as were the men with the highest blood levels of selenium. The authors concluded that selenium supplementation may be beneficial for the prevention of prostate cancer.
Prostate cancer is one of the major health concerns facing aging men. Any intervention that could help prevent this disease would, therefore, be an important advance.
Selenium is an essential trace mineral found in foods. The recommended dietary allowance for selenium is 55 mcg per day. Good food sources of selenium include seafood, grains, meat, garlic, mushrooms, and asparagus. The amount of selenium in plant foods is highly dependent on the selenium content of the soil in which it was grown. Most geographical regions in America, particularly the Midwest, have adequate concentrations of selenium in the soil, although subnormal levels may be found in parts of the Pacific Northwest and elsewhere.
Supplementation with excessive amounts of selenium can cause hair loss and nail sloughing; in rare cases, neurological problems and even death have resulted from taking too much selenium. A recent report from the National Academy of Sciences selected 400 mcg per day as the tolerable upper limit for selenium supplementation. The best form of selenium for supplementation is still open for debate, although previous cancer prevention studies have used high-selenium brewer’s yeast.
This new study is neither the best-designed nor the first to conclude that selenium may prevent prostate cancer. Studies similar to the new report, and with many more participants, have also found a reduction in prostate cancer incidence in subjects with high blood or toenail concentrations of selenium.2 3 4 A clinical trial published in 1996 showed that supplementation with 200 mcg of selenium per day from high-selenium brewer’s yeast reduced the incidence of prostate cancer by 63%.5
A definitive answer to the question of whether selenium supplementation prevents prostate cancer may be available soon. There is an ongoing clinical trial in which 32,000 men will take either selenium or placebo for 12 years. These results will likely give more definitive information about the safety and efficacy of selenium for cancer prevention.
1. Brooks JD, Metter EJ, Chan DW, et al. Plasma selenium level before diagnosis and the risk of prostate cancer development. J Urol 2001;166:2034–8.
2. Yoshizawa K, Willett WC, Morris SJ, et al. Study of prediagnostic selenium level in toenails and the risk of advanced prostate cancer. J Natl Cancer Inst 1998;90:1219–24.
3. Nomura AM, Lee J, Stemmermann GN, Combs GF. Serum selenium and subsequent risk of prostate cancer. Cancer Epidemiol Biomarkers Prev 2000;9:883–7.
4. Morris JS, Pressel S, et al. Prediagnostic serum selenium and risk of cancer. Lancet 1983;ii:130–4.
5. Clark LC, Combs GF, Turnbull BW, et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. JAMA 1996;276:1957–63.
Matt Brignall, ND, is in practice at the Seattle Cancer Treatment and Wellness Center and at the Evergreen Integrative Medicine Clinic in Kirkland, WA. He specializes in integrative treatment of cancer. He is a contributor to Healthnotes and Healthnotes Newswire.
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