Selenium is a trace mineral that is essential to good health but required only in small amounts. It is incorporated into proteins to make selenoproteins, which help prevent cellular damage from free radicals. Besides its antioxidant activity, selenium also has immunomodulatory, anti-carcinogenic and anti-atherogenic activities. The content of selenium in food depends on the selenium content of the soil where plants are grown or animals are raised. Rich sources are Brazil nuts, tuna, cod, beef, turkey and chicken breast. Recommended daily allowance is 20-70 micrograms/day based on age. (For more detailed information, please visit ISM’s searchable database: Nutraceutical Search.)
Increasing the daily intake of selenium from dietary and supplementary sources, could cut the risk of bladder cancer by 70 per cent. After accounting for sex, age, smoking and occupational exposure, the researchers calculated that the risk of bladder cancer was slashed by 70 per cent for those people with blood levels of more than 96 micrograms per litre, compared to those with serum levels of less than 82.4 micrograms per litre. [E. Kellen, International Journal of Urology 2006 Vol. 13, pp. 1180-1184.]
Interventions with Se have shown benefit in reducing the risk of cancer incidence and mortality in all cancers combined, and specifically in liver, prostate, colorectal and lung cancers. The effect seems to be strongest in those individuals with the lowest Se status. [Eliane Kellen, Proc Nutr Soc. 2005 Nov; 64(4): 527-42.]
Mechanism study showed that selenium-rich amino acids could increase the generation of intracellular reactive oxygen species (ROS) concentration-dependently. Antioxidant N-acetylcyteine partially inhibited the increase of ROS. Those results suggested that Se-rich amino acids were effective carcinostatic agents compared with sodium selenite and selenomethionine. [Life Sci. 2005 Sep 9; 77(17): 2098-110.]
Men and women taking selenium supplements for 10 years had 41% less total cancer than those taking a placebo. Although more than a hundred of animal and dozens of epidemiological studies have linked high selenium status and cancer risk, this is the first double-blind, placebo-controlled cancer prevention study with humans that directly supports the thesis that a nutritional supplement of selenium, as a single agent, can reduce the risk of cancer. Overall, the selenium group experienced 18 percent less mortality than the placebo group. [Larry Clark, Journal of the American Medical Association, Jan. 1, 1997]
In a clinical setting, cancer correlates inversely with patient’s blood Se. [Willett, Lancet (1983) II:130-4]
Total cancer mortality is 3X higher in persons with low Se. [Yu, Biological Trace Element Research (1985) 7:21-9]
Those people in lowest 10% of Se in blood have 6X incidence of cancer. [Clark, Nutrition & Cancer (1984) 6:13-21]
Se should be considered not just as a preventive, but also as a therapeutic acting additively or synergistically with radio & chemo therapy. [Milner, Journal of Food Chemistry (1984) 32:436-42]
Selenium appears to increase cancer cell death by causing apoptosis. [Helzlsouer, J Natl Cancer Inst (2000);92:2018-23]
Selenium is a protective element in a cancer prevention diet. [Cancer Causes and Control. 2005 Nov; 16(9): 1125-31.]
Harvard University researchers conducted a seven-year study of 33,737 male health professionals, which found an association between higher selenium levels and reduced risk of advanced prostate cancer. After accounting for all other influencing factors (age, weight, vasectomies, diabetes, smoking, and family history), the researchers concluded that men with the highest levels of selenium in their bodies had only one-third the risk of developing advanced prostate cancer. [Journal of the National Cancer Institute, August 1998]
Preclinical, epidemiological, and phase III data from randomized, placebo-controlled clinical trials suggest that both selenium and vitamin E have potential efficacy in prostate cancer prevention. [Ann N Y Acad Sci. 2004 Dec; (1031): 234-41.]
Increasing Se dietary intake is associated with a reduced the risk of prostate cancer. [Nomura, Cancer Epidemiol Biomarkers Prev (2000);9:883-7 and Brooks, J Urol (2001);166:2034-8]
Low serum levels of selenium confer a four- to five-fold increased risk of prostate cancer. [Brooks JD, et al. J Urol 2001 Dec;166(6):2034-8]
Selenium treatment significantly reduced prostate cancer incidence by 63%. [Clark LC, et al. Br J Urol 1998 May;81(5):730-4]
Supplementing with 200 micrograms of selenium daily reduced men’s risk of developing prostate cancer three-fold, compared to a placebo group whose normal dietary intake was estimated to be about 90 micrograms/day. [Giovannucci, E, et al. The Lancet 1998 Sep 5;352:755-56]
Men who had taken selenium for 6½ years had approximately 60 percent fewer new cases of prostate cancer than men who took the placebo. In 2002, study data showed that men who took selenium for more than 7½ years had about 52 percent fewer new cases of prostate cancer than men who took the placebo. [Clark LC, Nutritional Prevention of Cancer Study Group. Journal of the American Medical Association 1996; 276(24):1957–1963; Duffield-Lillico AJ, A summary report of the Nutritional Prevention of Cancer Trial. Cancer Epidemiology, Biomarkers & Prevention 2002; 11(7):630–639.]
Higher blood levels of selenium may reduce the incidence of skin cancer by about 60 per cent. [van der Pols, JC et al (2009).Serum Antioxidants and Skin Cancer Risk: An 8-Year Community-Based Follow-up Study. Cancer Epidemiology Biomarkers & Prevention , 18(4), 1167-73.]
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