Selenium Very small quantities of the trace mineral selenium are essential to human health. Selenium is required for the synthesis of the protective enzyme glutathione peroxidase, which protects cell membranes against damage by oxidants, including those in cigarette smoke. Selenium also seems to make platelets less sticky, decreasing the risk of heart attacks and strokes. It may also boost cellular immunity. There is now a large body of evidence to suggest that in countries with high levels of selenium in the soil, cancer rates are low.
Studies show that healthy people have higher selenium blood levels than cancer patients.
And there is a substantial body of evidence to suggest that selenium supplements, either in the diet or added to the drinking water, offer protection against a variety of forms of cancer. Studies on the protective effects of selenium have generated a great deal of excitement among researchers. It has been the most widely studied mineral in recent years. Selenium also helps detoxify some of the toxic heavy metals in cigarette smoke, such as mercury and cadmium. A study led by Dr. Walter Willett of the Harvard School of Public Health found that people who came down with certain types of cancer had low selenium blood levels several years prior to the discovery of their cancers.