Selenium is a mineral that acts as a powerful antioxidant and free radical scavenger.  It is a great protector and detoxifier; this is because it is required for the production of glutathione peroxidase, an enzyme necessary for detoxification and protection of the body against free radical damage.

Free radicals are produced in the body from toxic chemicals, excess sugar intake, smoking, pollution and stress. Free radicals are capable of causing damage to the DNA inside cells.  This speeds up the aging process and increases the risk of cancer.

Selenium has been shown to stimulate apoptosis (cell death) in tumor cells, and a low selenium status predicts a poorer outcome in those with certain cancers.

Geographic studies have shown that people who live in areas with selenium deficient soils and have a low selenium intake have higher cancer mortality rates. Lower body stores of selenium have been found in women who have had mastectomies.

Women who have the BRCA1 gene, which is a mutated gene that places them at greatly increased risk of breast cancer are known to have more chromosome breaks (which can promote cancer) than women without this gene. Research has shown that when women with the BRCA1 gene were given supplemental selenium for three months, their number of chromosome breaks was reduced to normal.

Obtaining adequate selenium from diet alone is very difficult because very few foods are a rich source of selenium.  Brazil nuts, crab and salmon provide some selenium, however using a selenium supplement will ensure you receive optimal levels of this vital mineral. For more information on reducing the risk of breast cancer, see the book The Breast Cancer Prevention Guide.

Reference:
Kowalska E et al., Increased Rates of Chromosomes Breakage in BRCA1  Carriers are Normalized by Oral Selenium Supplementation, Cancer Epidemiology Biomarkers and Prevention 2005