The recent Nutritional Prevention of Cancer Study published by Clark et al. in JAMA (Vol. 276 (24), 1996) indicated convincingly that selenium supplementation is beneficial in reducing the incidences of different cancers.
The study randomized 1312 patients (with a previous history of basal or squamous cell carcinomas of the skin) to receive a placebo or 200 µg selenium per day. Patients were treated for an average of 4.5 years, with a follow-up of 5.4 years.
The primary end points for the trial were the incidences of basal or squamous cell carcinomas of the skin. Secondary end points included the incidences of lung, prostate and colorectal cancer, total cancer incidence and all-cause and total cancer mortality.
Selenium supplementation did not significantly affect the incidence of skin cancers. However, compared with the controls, patients treated with selenium had significantly reduced incidences of lung, prostate and colorectal cancer.