Selenium supplementation reduces liver cancer incidence by 35% in a community with low baseline selenium status, but may increase the risk of type 2 diabetes in individuals with high baseline plasma selenium levels.

Similarly, an enriched selenite salt supplementation in a community of 21,000 persons in China reduced liver cancer by 35% [55]. A 200 μg of selenium per day intake during 7 years decreased prostate cancer among participants in a Nutritional Prevention of Cancer (NPC) trial [62]. However, it was noted that the results of the NPC test also showed an increased risk of type 2 diabetes mellitus among participants with plasma selenium concentration in the upper tertile at the beginning of the study.