Selenium
Overview
An important component of the antioxidant enzyme called glutathione peroxidase, selenium works in conjunction with vitamin E to ensure cell membranes are not damaged by free radicals. Found in all of the body tissues, selenium is known to be concentrated mainly in the kidneys, liver, pancreas, testes and spleen.
Selenium became a popular topic in the 1970s and 1980s when scientists finally came to realize that selenium was not a toxic substance, but one which the human body requires.
Sources of Selenium
Selenium is transferred from the soil where it is found into food sources such as the plants and vegetation humans consume. Selenium can also be acquired from eating meat from the animals which consume these plants. However, the level of selenium in the soil varies tremendously from one region to another. Also, much of the selenium which is contained in natural foods is “processed out” as the vegetation is prepared for sale and shipment. A good example of this processing loss is when manufacturers make white flour or white rice, where the loss of important vitamins and minerals is extensive.
Selenium can also be found in some drinking water and can be added to drinking water in areas where selenium in the soil is known to be deficient. Some shampoos and lotions for the skin contain selenium: it is thought this use may provide small amounts of selenium for use in the human body.
Natural health practitioners have long been aware of the benefits provided by brewer’s yeast and wheat germ for their selenium contents. It is possible to consume selenium through eating wholesome foods such as barley, oats, whole wheat, brown rice, molasses, and nuts, with Brazil nuts having especially high concentrations of selenium.
Selenium can also be found in butter, most fish and lamb. Salmon, halibut and snapper also have high levels of selenium, as well as tomatoes, radishes, broccoli, garlic, onions, mushrooms and Swiss chard.
Functions of Selenium
At present selenium appears to have numerous functions for the human body. Current research is centered upon selenium and the protein enzymes called selenoproteins. The best known of these proteins is glutathione peroxidase, or GPO. Researchers now know that selenium is an important part of a nutrition-based antioxidant system which works to protect intracellular structural membranes and cell membranes from lipid peroxidation. The enzyme action of this particular process can prevent degeneration of cells from free radicals.
GPO is also known to aid in the metabolism of red blood cells and has been confirmed to prevent chromosome damage to cultures involving tissue samples. Many of the research studies being conducted in labs around the world revolve around the fact that this enzyme process helps to slow or even prevent the aging process, thereby retaining the elasticity of the skin.
Uses of Selenium
While the anti-aging aspects of selenium consumption can branch off into many areas of use for the human body, selenium also can be used to stimulate the formation of antibodies in response to vaccines. This effect seems to be enhanced by using vitamin E in conjunction with selenium. In fact, studies have shown that selenium and vitamin E used together can increase the formation of antibodies by 20 to 30 times.
While more research needs to be completed regarding the effects of selenium on the cardiovascular system, studies have shown geographical areas with low selenium have a higher incidence of strokes and other related conditions.
Perhaps most importantly, selenium has been found to have anti-carcinogenic properties. Studies have shown low levels of selenium in the blood and tissues may correlate with increased risks of cancer more than any other substance in the body. Current thought centers on the antioxidant properties of selenium as providing healthier cells and tissues.
In one study using rats which were exposed to a potent carcinogen, a mere 15 percent of the rats who were also given selenium developed liver cancer. Eighty-five percent of the rats who did not receive selenium were stricken with liver cancer.
Tests from as far back as 1969 conclusively showed that the majority of cancer patients have extremely low levels of selenium in their bodies.
Some studies have also shown individuals with higher levels of selenium show less adverse reaction to common toxic exposures such as oxidized fats, smoking, alcohol consumption and exposure to cadmium and mercury.
Selenium may also aid in the synthesis of proteins, which directly affect a body’s development and growth.
Further research is needed, but selenium may be helpful in the treatment of severe cases of acne. In particular the use of selenium sulfide seems to be beneficial in the treatment of dandruff and dermatitis and for overall improvement in the skin’s health.
Selenium Deficiency
Selenium is known to play an important role in the production of thyroid hormone. Low thyroid hormone production can be directly attributed to selenium deficiency.
Deficiencies of selenium can lead to autoimmune disease, recurrent illnesses and infection, as well as inflammatory problems. Not enough selenium in the body can also lead to increased instances of cancer, especially cancers related to the liver, breasts, lungs, ovaries, bladder, prostate, pancreas, colon/rectum and skin.
It is now thought that the absorption of selenium may decrease with age. This condition, combined with the lessened nutritional habits of many elderly people, can lead to selenium deficiencies. As selenium is known to impede the aging process, older individuals should try to be more aware of their selenium intake.
Required Daily Amount
While selenium requirements went unnoticed for many decades, the National Academy of Sciences established daily nutritional guidelines for selenium in 2000. Selenium intake should fall somewhere between 50 and 200 mcg, which also happens to be fairly close to the range most individuals will find naturally in water and natural foods. Conservatively speaking, a safe amount for children is between 30 and 150 mcg per day and between 100 and 200 mcg daily for adults.
It is possible that men will need more selenium than women, and in particular sexually active men.
As the antioxidant properties of selenium are synergistic, an individual may wish to consume vitamin E along with the selenium.
References
- Alan H. Pressman and Sheila Buff. The Complete Idiot's guide to vitamins and minerals, Alpha A member of Penguin Group (USA) Inc (2007)
- Brewer, S. The essential guide to vitamins, minerals and herbal supplements, Right Way (2010)
- Elson M. Haas, Md & Buck Levin, Phd, Rd. Staying Healthy with Nutrition: The Complete Guide to diet and nutritional medicine, Celestial Arts (2006)
- Holford, P. The optimum nutrition bible, Little Brown Group (2004)
- Holford, P & Lawson, S. Optimum Nutrition Made Easy How to achieve optimum health, Piatkus Books (2008)
- Lieberman, S. & Bruning, N. The Real Vitamin & Mineral Book, Avery, a Member of Penguin Group (USA) Inc (2003)
- Rodale Health Books. Healing with vitamins : the best nutrients to slow, stop, and reverse disease, Rodale, (2009)
- Royston, A. Vitamins and minerals for a healthy body, Heinemann Library, (2003)
- The National Research Council. Recommended Dietary Allowances, 10th ed, National Academy of Sciences (1989)
- Werbach, M. Nutritional Influences on Illness, 2nd ed, Third Line Press (1993)
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