Most people get their intake of this important mineral from the foods they eat, as it is derived from soils where food is grown. There are a few notable exceptions – the United Kingdom has notoriously low levels, while Keshan Province in northeast China made selenium famous because the selenium levels in the soil are so low that people in the region suffer from what is called Keshan disease, which manifests as enlarged hearts and has killed about 30 percent of mothers of children with the disease. Selenium has been found to prevent the disease, but not reverse it.1
There are two main reasons why people should take selenium: One is its utility as an antioxidant – it is the “S” in the ACES antioxidant formulas that also contain vitamins A, C and E. Vitamin E and selenium were linked together early in the research history of selenium as a nutrient. The reason was that both nutrients exert antioxidant effects, though by different mechanisms. One idea that arose was that vitamin E stops free radical-initiated oxidant reactions, while selenium, via the enzyme glutathione peroxidase, prevents certain radicals from forming by eliminating hydrogen peroxide, which can produce radicals.
The other benefit of selenium is its ability to reduce the likelihood of prostate cancer, which is important for men's health. For prostate cancer prevention, 200 micrograms (1/1,000 of a milligram) a day is sufficient, while 300 micrograms is seen as the upper tolerable level. A handful of Brazil nuts is a tasty alternative. A 1996 study in the Journal of the American Medical Association found that selenium reduced colon, lung and prostate cancers by between 50 and 63 percent.2 This led to a 2003 FDA-minted health claim for selenium and prostate cancer.
However, a 2009 JAMA paper found selenium to not have an effect on prostate cancer, and what’s more, the so-called SELECT study was stopped in midstream because researchers found a tiny increase in diabetes incidence among those taking selenium.3
Lost in translation in these studies and attendant government pronouncements is that there are actually a number of different types of selenium. The National Cancer Institute in the SELECT study used selenomethionine, which is chemically well-defined, with only one free compound. These are the sort of simple compounds favored by pharmaceutical researchers, because they are so easy to characterize. Meanwhile, the studies that show a benefit on cancer invariably have used high-selenium yeast, which contains a range of selenium compounds organically bound to proteins in the yeast that protect the selenium from oxidation.
There is, in fact, a study currently under way is comparing the maligned selenomethionine with the high-selenium yeast. Unfortunately, the results are not expected until perhaps 2013. Until then, the establishment medical world will likely cast aspersions on selenium for cancer prevention.
Recent good news: The Spanish National Cancer Research Center did a meta-analysis (combining the findings or numerous other studies to look for trends that may have been overlooked) of seven previous studies on selenium. Here's what they said in the report: "Results suggest a beneficial effect of high selenium intake for bladder cancer risk. The lower the levels of selenium, the higher the risk of developing bladder cancer."
The effect was seen mostly in women who took the supplement. You can read more about the selenium study here.
In the meantime, selenium is still undisputed as an antioxidant and will continue to find a home in antioxidant formulations. The FDA in 2009 approved its use in foods such as cereals and nutrition bars, and in 2010 a coalition of natural-product advocates successfully filed suit against the FDA for it's denying of the use of qualified cancer prevention health claims by selenium manufacturers. The FDA was requiring
The coalition said “The FDA was indeed violating freedom of speech by saying that no cancer-related health claims about the selenium could be made unless the science was completely conclusive or unless ridiculous and misleading disclaimers were added to the message.”
Disclaimer: The information provided in this section is a public service of WellWise.org, and should not in any way substitute for the advice of a qualified healthcare professional and is not intended to constitute personal medical advice.