Nutritional Prevention of Cancer Study Group also performed a study in 1312 patients to test whether or not 200 mcg of selenium would prevent non-melanoma skin cancer in a randomized, double-blind, placebo controlled trial, but it was found that squamous cell skin cancer risk was increased by 25%, and non-melanoma skin cancer by 17% by calculating a hazard ratio (19).
Effects of a selenium, beta-carotene, and vitamin E combination::
Ten-year follow-up results from the General Population Trial, a study conducted in in Linxian, China from 1985 to 1991 that gave daily vitamin and mineral supplements (50 mcg of selenium, 30 mg of vitamin E, and 15 mg of beta-carotene) to 29,584 adults at high risk of esophageal and stomach cancers were presented. In the original study, researchers had found that treatment led to a decrease in mortality from all causes, cancer overall, and gastric cancer. Adding to these important findings, post intervention follow-up indicated that the beneficial effects of the beta-carotene–vitamin E–selenium combination in the General Population Trial remained evident up to 10 years after the intervention. Cumulative mortality decreased from 33.62% to 32.19% and cumulative gastric cancer mortality decreased from 4.28% to 3.84%. These benefits were consistently greater in participants who were younger (<55 y) at the beginning of the intervention. (8)