About Selenium
Selenium, atomic symbol Se, is one of the 109 stable (non-radioactive) elements of the Periodic Table and one of the nine well known essential trace elements, Fe, Cu, Zn, I, etc, for animals and people. Se was discovered in 1817 by the Swedish chemist, Jon J. Berzelius. Se remained a nutritional unknown until 1957 when Klaus Schwarz working at the National Institutes of Health found that it prevented a liver disease in rodents. Over the next decade Se was found to be required by many animal species. In 1973 a graduate student, John Rotruck, at the University of Wisconsin discovered Se to be an integral component of a rodent enzyme, glutathione peroxidase. With this discovery and the finding that glutathione peroxidase was almost in every animal and human cell, the US Food and Drug Administration permitted Se supplementation to most animal feeds by then known to be low in Se content accounting for the various diseases in animals. The first recognized human disease of low Se intake occurred in China, a heart disease, named Keshan disease for the county in which the disease was first identified in 1980. By the end of the decade the National Academy of Sciences in 1989 made a dietary recommendation (RDA) to the American people to consume 70 mg Se/day. This recommended amount of dietary Se was reduced to 55mg Se/day in 2000. The later is not much higher than the World Health Organization’s minimum recommended amount of dietary Se for adults, 40 mg Se/day.
Now almost fifty years after the discovery of the dietary requirement of Se and over 16 thousand research papers being published on Se what can we say about the benefits of Se? We can say that humans need Se in their diet for 25 different proteins; among these are several related versions of the powerful antioxidant enzyme family of glutathione peroxidases. We can say that most Europeans, Brits, Australians, New Zealanders, Scandinavians, Indians, Bangladeshi, and a lot of Chinese do not get what is considered by most nutritionists today to be enough Se in their native diets. Americans, Canadians, Japanese and other peoples usually get enough Se in their diets to meet their minimal requirements. The variations in dietary Se by country are related to the Se content of soils in which food and fiber are produced.
We can say that human dietary supplementation with Se at a minimum of 200 mg Se/day, based upon the preponderance of animal experimentation and more limited human experimentation; probably improves immune responses, including reduction of bacterial and viral infections and severity thereof, reduction of possible heart diseases, reduction of most cancers, but especially, breast, prostate, lung and liver cancers, and possibly reductions in Alzheimer’s and associated dementias. Of all tissues priority for Se appears from the research to be the cells of the immune system and the brain.
We can say with much confidence how Se works to account for the effects described above. Some effects are do to the antioxidant Se properties within enzymes, like the glutathione peroxidases. Others are do to Se in non-enzymatic proteins while some are do to the formation of specific and highly reactive metabolites, i.e. products of the various dietary sources of Se.
We can say rather confidently today what forms of Se are in various foods. Modern analytical techniques permit identification of specific Se components in foods as well as supplements. In short, an amino acid, selenomethionine dominates the variety of selenium components in foods bring found in both plant and animal foods. Another amino acid, selenocysteine is second in abundance in most foods. Another amino acid, Se-methylselenocysteine, SeMC TM, found in very small amounts in garlic, broccoli, onions and other Cruciferous and Allium plant foods appears to have potent cancer prevention properties not shared with other food components. Most foods contain other very small amounts of Se components. All this information is well documented in the scientific literature and disease prevention literature can be found in the reference section of this website.
Se is the most fascinating of all the trace elements because of its very special chemistry not shared by any other element. One of the reasons there are more than 16 thousand scientific publications about Se is the special chemistry in which Se can be made to change its chemical state of existence and the immediate environment affecting metabolism of many diseases. Take the time to read more about Se from the web references provided or the many well written reviews some of which are provided below.