Review on the health-promoting effect of adequate selenium status

Abstract

Selenium is an essential microelement involved in various biological processes. Selenium deficiency increases the risk of human immunodeficiency virus infection, cancer, cardiovascular disease, and inflammatory bowel disease. Selenium possesses anti-oxidant, anti-cancer, immunomodulatory, hypoglycemic, and intestinal microbiota-regulating properties. The non-linear dose-response relationship between selenium status and health effects is U-shaped; individuals with low baseline selenium levels may benefit from supplementation, whereas those with acceptable or high selenium levels may face possible health hazards. Selenium supplementation is beneficial in various populations and conditions; however, given its small safety window, the safety of selenium supplementation is still a subject of debate. This review summarizes the current understanding of the health-promoting effects of selenium on the human body, the dietary reference intake, and evidence of the association between selenium deficiency and disease.

Keywords: health-promoting effects; inorganic selenium; organic selenium; selenium intake; selenium status.

FIGURE 1

Structures of common inorganic and organic selenium compounds. Sodium selenite (A), sodium selenate (B), SeC (C), and SeM (D).

FIGURE 2

Health-promoting effects of selenium and its mechanisms of action. Selenium possesses anti-oxidant, anti-cancer, immunomodulatory, hypoglycemic, and intestinal microbiota-regulating properties. It acts as an anti-oxidant by lowering oxidative stress and deoxynucleotide levels. It functions as an anti-cancer agent by inducing apoptosis and cell-cycle arrest, preventing tumor cell invasion and metastasis, and promoting DNA damage repair. It exerts immunomodulatory effects by affecting non-specific immunity (e.g., macrophages and neutrophils) and specific immunity (e.g., T and B lymphocytes). It exerts hypoglycemic action by regulating the IRS-PI3K-Akt signaling pathway. It regulates the intestinal microbiota by regulating prostaglandins.

FIGURE 3

Beneficial effects and mechanisms of selenium supplementation in various diseases. Selenium supplementation can provide protection for populations with AIDS, cancer, CVD, and IBD. Supplementing HIV-infected people with 200 μg selenium per day enhanced the CD4 count, stimulated CD4 + T cell differentiation into T helper 1 cells, and decreased the HIV-1 viral load, thus decreasing HIV incidence and enhancing patient survival. Supplementing prostate cancer patients with 200 μg of selenium per day prevented cell carcinogenesis, enhanced the body’s immunity and anti-oxidant capacity, and reduced the incidence and mortality of prostate cancer. In a CVD population, supplementation with 200 μg selenium per day reduced lipid oxidation, platelet aggregation, and inflammation, thus decreasing CVD morbidity and mortality. Supplementing an IBD population with 200 μg of selenium per day relieved intestinal inflammation and restored epithelial barrier integrity, thereby decreasing the incidence, severity, duration, and risk of IBD-associated colon cancer.