Selenium Supplements May Reduce the Risk of Breast Cancer in Women Genetically at Risk

by | Jul 24, 2008 | 2005, Breast Cancer, Cancer, Selenium

Written by Susan Sweeny Johnson, PhD, Biochem. DNA breaks decreased significantly after selenium supplementation. 

Some inherited previously identified genetic mutations predispose women to develop breast cancer.(1-4)  One of the most well known mutations is in the BRCA1 gene where 80% of women with this mutation will develop breast cancer during their lifetime. (5,6) The BRCA1 mutation causes a defect in DNA repair such that naturally occurring breaks in DNA stimulated by environmental factors such as radiation, chemicals or oxidation are not repaired properly. Unrepaired DNA breaks increase the likelihood that cells will become cancerous. (7)

Selenium has been shown to protect against oxidative DNA damage and to enhance DNA repair. (8) In this study, women with BRCA1 mutations were given oral selenium to see if their lymphocyte cells could be protected from chemically induced DNA breaks. A sample of their lymphotcytes were taken from the subjects and then treated with the chemical, bleomycin, which cause double-stranded DNA breaks.

In order to determine the baseline susceptibility of BRCA1 carriers to DNA breaks, 26 pairs of women were studied without selenium supplementation. In each pair, a BRCA1 carrier was compared to a close relative of similar age who was not a BRCA1 carrier. The mean number of induced breaks per cell was significantly higher in BRCA1 carriers than in their normal counterparts.

To determine if selenium supplementation could reduce the number of induced DNA breaks in BRCA1 carriers, 35 carriers were given oral selenium (280 micrograms of pure selenium as sodium selenite dissolved in 70% ethanol per day). Blood and lymphocyte samples were taken before and after an average of 1.5 months of supplementation.  The blood levels of selenium rose about 50% after supplementation. Chemically induced DNA breaks in BRCA1 carriers decreased significantly after selenium supplementation to approximately normal levels for non-carriers.

Further larger studies should be performed to substantiate these results but in this study selenium supplementation well below unsafe levels seems to help BRCA1 carriers prevent excessive DNA breaks that are correlated with cancer formation.

Source: Kowalska, Elzbieta, et al. “Increased rates of chromosome breakage in BRCA1 carriers are normalized by oral selenium supplementation.” Cancer Epidemiology and Prevention Biomarkers 14.5 (2005): 1302-1306.

© 2005 by the American Association for Cancer Research.

Posted July 24, 2008.

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