Background: Breast cancer is the second most common cancer among women and one out of every eight women will be diagnosed with breast cancer. Selenium as a micronutrient in the diet is an important factor in the production of antioxidant enzymes that may affect cancer progression. Considering the "cancer tsunami" in Iran and also the prevalence of Selenium deficiency in some provinces, we decided to investigate the relationship between this micronutrient and breast cancer in order to reduce the incidence of the disease and treatment costs by Selenium supplementation.

Materials and Methods: Academic databases (e.g. Scopus, Pubmed, Google scholar and ScienceDirect) were searched.

Results: Studies showed that a selenium supplementation reduced the breast cancer mortality rate in some nutrition intervention trials. A one-unit increase in serum Selenium levels reduced breast cancer risk up to 7%. Selenium is able to strengthen the function of tight junctions in human endothelial cells this has been proved to be true about human breast cancer cells.

Conclusion: Our studies show that Selenium is a preventive agent for breast cancer. Also, Selenium supplementation is an important protective factor in the treatment of this illness and reduces the risk of developing breast cancer.