Opportunities for Selenium-Enhanced Foods In Cancer Prevention.

Selenium (Se) is an essential constituent of some two dozen selenoproteins.  Se status has been inversely associated with cancer risk, and Se-intervention has been found to reduce cancer risk in a wide variety of animal tumor models.  Most clinical trials have shown cancer risk reduction due to Se, particularly for non-deficient individuals with plasma Se levels less than ca. 120 ng/ml.  Se intakes vary widely between countries; substantial numbers of people in most countries appear to be of sub-optimal Se status, and low Se status is thought to be prevalent in almost half of the globe.  The Se contents of foods vary widely, tending to reflect the soil Se conditions where food and feed crops are produced.  The main sources of dietary Se for most people are cereals, meats and fish.  Thus, Se intakes in many countries can be affected by grain imports from the world market, most of which comes from the relatively Se-rich areas of North American and Australia.  Selenium-fertilization of food and feed crops may be an effective and sustainable means of increasing Se intakes. Best immediate results are generally obtained using selenate, foliar application being more effective than application to soil.  Se-fertilization has been used to enhance the cancer-protective actions of Se-enriched garlic, broccoli in animal models; these effects have been attributed to plant production of methylated selenides, which are thought to mediate Se-anticarcinogenesis.  Therefore, producing Se-enriched foods for reducing cancer risk is feasible.  Guidelines for doing so in a safe and efficacious manner will be discussed.