The World Health Organization suggests that 50-200 micrograms of selenium a day can prevent many diseases. The anti-cancer experiment conducted by the University of Arizona in the United States shows that among people who take 200 micrograms of preparation every day, the total cancer mortality rate is reduced by 50%, the total incidence rate is reduced by 37%, the incidence rate of prostate cancer is reduced by 63%, the incidence rate of colon cancer is reduced by 58%, and the incidence rate of lung cancer is reduced by 46%. Especially for people with low selenium concentration in the body, this auxiliary antimutagenic effect of selenium is more obvious.