Selenium: The Unsung Cancer-Preventing Wonder?

Selenium: The unsung cancer-Preventing wonder?

The mineral selenium has not achieved a 'trendy' status in the world of food marketing on par with Vitamin C or calcium. Yet this unsung nutritional component has been linked to lowering an individual's risk for cancer, independent of other lifestyle factors in studies since the 1990s. One double-blind cancer prevention study comprised 1,312 randomized patients, who were given either a placebo or a 200-microgram daily supplement of selenium per day "twice the average amount these Americans consume in their diet, thereby tripling their selenium intake" (Lang 1997). Only 69 members receiving the supplement developed any form of cancer versus 116 who contracted some form of cancer in the experiment's placebo group. The results were especially promising regarding the most common forms of cancer. "Prostate, esophageal, colorectal and lung cancer rates were among the most dramatic: patients in the selenium group had 71%, 67%, 62 and 46% reductions in cancer rates, respectively, than the placebo group"(Lang 1997).

Selenium levels vary widely amongst different population groups, based upon food choices and differences in food preparation, soil quality, and water. "Even Americans with the lowest selenium intake of 60 to 80 micrograms per day -- those living along the Southeastern seaboard and in the Pacific Northwest -- ingest two to five times more than citizens of New Zealand and 10 to 20 times more than people living in some areas of China" (Lang 1997). Foods high in the mineral include seafood; mushrooms; egg yolks; poultry; kidney, liver and muscle meats; vegetables and fruits like garlic, onions, broccoli, asparagus, and tomatoes; and also whole grains (Black 2006). But the amount within these substances can vary widely, depending on the amount of the mineral in the soil or water. "The selenium content of food is largely dependent on the content of volcanic ash in the soil on which the food was grown, with higher volcanic ash content yielding higher selenium levels. Soil that is irrigated by seawater, such as much of California's cropland, also contains higher levels of selenium" (Black 2006). Brazil nuts, grown in selenium-rich Brazilian soil, are some of the most potent sources of the mineral. According to the National Institute of Health (NIH) "Brazil nuts may contain as much as 544 micrograms of selenium per ounce. They also may contain far less selenium. It is wise to eat Brazil nuts only occasionally because of their unusually high intake of selenium."

The reasons that selenium is so effective in cancer prevention are uncertain, although it has been speculated that it possesses anti-oxidant properties, "especially when used in conjunction with vitamin C, vitamin E and beta-carotene" and "works to block chemical reactions that create free radicals in the body (which can damage DNA and cause degenerative change in cells, leading to cancer)" (Black 2006). Selenium has also been found to prevent damaged DNA molecules from reproducing, thus preventing the development of tumors as well (Black 2006). This is supported by a University of Arizona-Cornell research team which linked low selenium levels in the blood to increased risk of precancerous neoplastic polyps in the colon (Lang 2010). A Cornell University study conducted in 1995 found that animals fed diets high in selenium had 50% fewer tumors than those fed diets of average selenium content.