Data suggests that a diet rich in selenium protects against cancers of the stomach, breast, esophagus, lung, prostate, colon, and rectum. According to Dr. Harold Foster, death rates in the USA for cancer are lower when blood selenium levels are high. One important study found that a high blood level of selenium is associated with a 4-5-fold decrease in the risk of prostate cancer. Scientists at Stanford University studied 52 men who had prostate cancer and compared them to 96 men who didn’t. One surprising finding was that blood levels of selenium generally decreased with age. It is well known that the risk of prostate cancer increases dramatically as one ages.
 Foster HD. “Landscapes of Longevity: The Calcium-Selenium-Mercury Connection in Cancer and Heart Disease,” Medical Hypothesis, Vol. 48, pp 361-366, 1997