Selenium


Selenium has become one of the most exciting nutrients of the 1970s and 1980s. Once classified solely as a toxic mineral, it is now regarded as an essential one, needed in small daily amounts. Selenium functions as a component of the enzyme glutathione peroxidase, which accounts for its antioxidant function and thus its important contribution to the prevention of the twentieth-century plagues, cancer and cardiovascular disease.


Low soil levels of selenium are associated with higher cancer rates, and soil-rich areas have below-average cancer rates for a number of body systems, particularly the breasts, colon, and lungs. Keshan disease, a form of heart disease prevalent in children and is characterized by an enlarged heart and congestive heart failure, may be a direct result of selenium deficiency, as it has responded well to selenium treatment. People in Keshan, China, where the disease was discovered, treat it with a common herb called Astragalus, which accumulates selenium from the soil.


As in the Keshan area of China, the soil in many parts of the United States is very low in this important mineral. Here, the western states generally have higher selenium levels than the eastern; South Dakota has the highest and Ohio the lowest. Ohio has more than twice South Dakota’s rate of a number of common cancers. Most states with high levels of soil selenium show a decreased rate of cancer deaths. There is some concern, though, that high amounts of selenium, particularly elemental selenium and inorganic sodium selenite, may be toxic in areas where it is found in high concentrations in the water and soil, such as South Dakota.


Selenium and vitamin E work together synergistically in that they carry out antioxidant and immunostimulating functions better together than individually; however, their mechanisms of action are probably not the same. Both of these nutrients are part of the “antiaging” or “longevity” group, which may be directly attributable to their antioxidant functions because tissue oxidation by free radicals may be the contributing factor to degenerative disease.


Despite its importance, there is less than 1 mg. of selenium in our body, most of it in the liver, kidneys, and pancreas and, in men, in the testes and seminal vesicles. Men have a greater need for selenium, which may function in sperm production and motility. Some selenium is lost through the sperm as well as through the urine and feces. It is absorbed fairly well from the intestines, with an absorption rate of nearly 60 percent.


Sources: Soil levels of selenium vary greatly from state to state and even within local regions across the United States, as well as from country to country throughout the world. So the amount of selenium in our food sources, whether consumed directly as plants or as meat from animals that have eaten the vegetation, varies according to the soil levels. Further, most selenium in foods is lost during processing, such as when making white rice or white flour.


Many natural foods contain selenium, mainly an organic form that is much less toxic than sodium selenite and definitely less so than elemental selenium. Selenium may be present in some drinking water, and it is sometimes even added to drinking water where it is deficient. We may see this more in the future as a general disease-prevention measure. Mother’s milk usually has several times more selenium than cow’s milk. Selenium is also used in some shampoos and skin lotions, and it is possible that we absorb small amounts of selenium from these products.


Brewer’s yeast and wheat germ, both regarded as “health foods,” usually contain high concentrations of selenium. Animal sources such as liver, butter, most fish, and lamb have adequate amounts. Many vegetables, whole grains, nuts, and molasses are fairly good selenium foods. Brazil nuts have high amounts; barley, oats, whole wheat, and brown rice are also good sources; and shellfish such as scallops, lobster, shrimp, clams, crab, and oysters are all rich in selenium. Garlic and onions, mushroom, broccoli, tomatoes, radishes, and Swiss chard may be good selenium sources if the soil in which they are grown contains it. Therefore, if we want to make sure we get adequate amounts of selenium and other minerals, it is best to eat a varied diet of wholesome foods.


Functions: Selenium has a variety of functions, and research is revealing new information. Its main role is as an antioxidant in the enzyme selenium-glutathione peroxidase. Selenium is part of a nutritional antioxidant system that protects cell membranes and intracellular structural membranes from lipid peroxidation. It is actually the selenocysteine complex that is incorporated into glutathione peroxidase (GP), an enzyme that helps prevent cellular degeneration from the common peroxidase free radicals, such as hydrogen peroxide. (Selenomethionine can be supplemented to generate the organically complexed and active selenocysteine.) GP also aids red blood cell metabolism and has been shown to prevent chromosome damage in tissue cultures. Solidification of tissue membranes may occur through the oxidation of fatty acids. As an antioxidant, then, selenium in the form of selenocysteine prevents or slows the biochemical aging process of tissue degeneration and hardening-that is, loss of youthful elasticity. This protection of the tissues and cell membranes is enhanced by vitamin E. The antioxidant effect may also benefit the cardiovascular system and protect against cancer. We need adequate daily amounts of selenium for the maintenance of these antioxidant functions and for selenium’s other cellular functions as well.


Selenium also appears to help stimulate antibody formation in response to vaccines. This immunostimulating effect is also enhanced by vitamin E; the presence of these two nutrients can increase antibody formation by 20-30 times, as shown by research.


Selenium is thought to offer protection against cardiovascular disease, possibly by its antioxidant function but possibly by another, as yet, unknown mechanism. Epidemiological studies show an increased incidence of strokes and other cardiovascular problems in many low-selenium areas.


Selenium is also being found to have an anticarcinogenic effect; its blood or tissue levels may correlate more closely with cancer risk than those of any other substance. Public health research shows this relationship in many cases; good selenium levels correlate with low cancer rates and low levels with increased cancer rates. I do not yet know exactly how this works other than possibly through the antioxidant function. Perhaps selenium decreases cell division or helps cell repair, or perhaps it protects against mutagenic changes in the first place.


Selenium also seems to protect us from the toxic effects of heavy metals and other substances. People with adequate selenium intake have fewer adverse effects from cigarette smoking, alcohol, oxidized fats, and mercury and cadmium toxicity. Aside from the likely antioxidant influence, the specific mechanism by which selenium affords this protection is not known, though the effect is confirmed by some research.


Selenium may also aid in protein synthesis, growth and development, and fertility, especially in the male. It has been shown to improve sperm production and motility. Thus, selenium may prevent male infertility; however, we do not know whether selenium deficiency will actually cause male infertility. These are only some of the conjectures about other selenium functions.


Uses: A growing number of clinically effective uses of selenium have been developed, and others are being tested for possible value. As part of nutritional antioxidant therapy with vitamin E, zinc, beta-carotene, and vitamin C, selenium, as selenomethionine (will form the active selenocysteine), may be beneficial in treating a variety of inflammatory problems and may be helpful in most acute or degenerative diseases to moderate the inflammatory process. Its use in treating arthritis and some autoimmune problems, such as lupus erythematosus or vasculitis, shows promise but needs further study. Selenium is known to help prevent cardiovascular disease and decrease the risk of complications such as strokes and heart attacks (possibly by reducing platelet aggregation) related to our number one disease process, atherosclerosis. This use, along with selenium’s confirmed ability to reduce the incidence of certain cancers, makes this trace mineral quite important.


Where selenium is abundant in the soil or when it is added to the diet, it has an anticarcinogenic effect. These conditions are associated with both decreased cancer rates and decreased cancer mortality, especially regarding the number one female cancer, that of the breast, but also cancer of the colon/rectum, prostate, lung, ovary, bladder, pancreas, and skin. This is a wide range. In animal studies, 1-4 ppm of selenium added to the food or water is clearly associated with decreased cancer rates. High breast cancer rates are associated with areas of low soil selenium in the United States, and human epidemiological studies confirm these findings throughout the world.


Because of selenium’s immunostimulating function, it’s very useful in the treatment of many immunosuppression diseases. With its antioxidant properties, selenium, especially along with vitamin E, may become a routine and powerful nutritional of treatment in the medical world. Autoimmune diseases, recurrent illnesses or infections, and other inflammatory problems may be helped by restoring adequate selenium levels in the body. Selenium can help us prevent disease by increasing our resistance. In some cases, selenium promotes more rapid recovery from many basic disease processes. More controlled human studies related to specific illnesses will need to be done to generate greater acceptance by the medical establishment of selenium’s important role.


Selenium’s postulated antiaging effect offers another possible use of the mineral; this cell-membrane-protecting influence on improving tissue elasticity also needs further research. With vitamin E, selenium also appears to be helpful in treating acne. Selenium sulfide used topically seems to help in certain skin conditions, such as dandruff and dermatitis, and to improve skin health. It is also a helpful treatment for the mild skin fungus tinea versicolor.


There are even more exciting possibilities for selenium’s use in heart diseases. One angina study showed reduced symptoms in nearly 100 percent of the patients when selenium was used in a dosage of 1 mg. per
day with 200 IUs of vitamin E, whereas the placebo group reported little benefit. Selenium supplementation helps correct the serious symptoms of Keshan disease, a cardiomyopathy (heart muscle disease with heart enlargement) associated with congestive heart failure and the resulting symptoms of body swelling, shortness of breath, and eventual circulatory collapse. This disease has been more prevalent in China, where it was first reported, but with our new knowledge, more cases are being found in other areas. It may simply be a disease of selenium deficiency. The antioxidant function of selenium likely decreases vascular clogging of inflamed artery linings by soothing irritation and binding free radicals; thus, selenium may play a role in reducing or preventing atherosclerosis at its initial biochemical level.


Some evidence suggests that selenium supplementation is also helpful in reducing menopausal symptoms. In addition, it has been suggested, with vitamin E, for male impotency. Although these uses need further study, it is certainly possible that selenium can increase sexual potency and fertility by improving sperm production and motility and by protecting against oxidative damage in the testes and related organs. (Fertility, potency, and sexuality are, however, more intricate than just these physiological processes.) I am sure that we will find more uses for selenium in the near future.


Deficiency and toxicity: Just 20 years ago, selenium was considered a nonessential toxic mineral. There is still justifiable concern over elemental selenium toxicity, but we are finding that the value of inorganic selenium salts, such as sodium selenite, and organically bound selenomethionine at appropriate levels far exceeds the potential to cause problems. Actually, selenium can be tolerated for short periods in higher amounts than was previously thought. Inorganic selenium, usually as sodium selenite, is the common form found in nature and can be more toxic in the short term than the organically bound selenium in the form of selenomethionine. While more than 1 mg. per day of sodium selenite is likely to produce symptoms, we may tolerate several milligrams daily of organic selenium without toxicity problems occurring. However, it is possible that the organic forms of selenium accumulate in the body and may be of long-term concern. Different authorities provide different figures for selenium intake and divergent viewpoints as to the question of toxicity; some sources state that toxicity is possible when 2,000 mcg. (2 mg.) are taken daily by people who already have total body stores of over 2.5 mg. (the normal level is 1 mg.), or when the water or food regularly contains over 5-10 ppm. Selenium is thought to interfere with sulfur compounds and even replace the sulfur in the body, as these two minerals are very similar biochemically, and thus may decrease a number of enzyme actions. The complexity of these issues in regard to selenium point out the importance of individual assessment and monitoring when taking certain supplemental products.


There is no clearly defined syndrome of selenium toxicity. Cattle that graze on selenium-rich soil have exhibited visual, muscular, and heart problems. Similar symptoms of toxicity have been found in humans living in high-selenium areas. Long-term ingestion of high amounts may cause problems with tooth enamel and strength, as higher selenium levels seem to increase tooth decay. One highly speculative theory is that selenium competes with fluoride in teeth, decreasing their strength. Other problems may include loss of hair, nails, and teeth, as well as skin inflammation, nausea, and fatigue. Some subtle symptoms that have been experienced include a garlic odor, metallic taste, or dizziness. Acute selenium poisoning can lead to fever, anorexia, gastrointestinal symptoms, liver and kidney impairment, and even death if the levels are high enough.


None of these symptoms should occur when selenium is taken in a therapeutic amount. There has been some fear of mutagenicity (that is, ability to cause developmental defects) of selenium in higher amounts. This might be true of the sodium selenite form, which may have both mutagenic and antimutagenic properties, depending on the amount. This theory needs further detailed study.


Selenium levels are frequently low in the soils of some regions and in certain Western diets. There appears to be problems associated with selenium deficiency; however, no clearly defined selenium deficiency syndrome has been accepted, although several theories postulate such a syndrome and evidence to support them seems to be mounting. Given selenium’s many important functions and uses, its deficiency may generate increases in many of the disease states that it can prevent and treat. With selenium deficiency, there may be increased risk and rates of certain cancers, cardiovascular disease, hypertension, strokes, myocardial infarction, and kidney disease-all heavyweights along death row. Other problems possibly associated with selenium deficiency include eczema, psoriasis, rheumatoid arthritis, cataracts, cervical dysplasia, alcoholism, and infections. As I have discussed, low soil selenium is related to higher cancer rates, and Keshan disease is likely a direct result of selenium deficiency.


Selenium deficiency is more common, of course, in areas of low soil selenium and also in infants fed cow’s milk instead of breast milk. Selenium absorption may be reduced with aging; in addition, older people often consume less selenium-containing fresh and whole foods.


Cataracts have been shown to contain only about one-sixth as much selenium as a normal lens; research is needed to determine whether this is a cause or a result of the cataract. Many books describe more rapid aging and decreased tissue elasticity with selenium deficiency, but this has not been confirmed with solid evidence. Many other metals, including cadmium, arsenic, silver, copper, and mercury, are thought to be more toxic in the presence of selenium deficiency.


We need to find better ways to evaluate body levels of selenium. Blood levels are not easy to evaluate, as they are low and much of selenium is stored. Hair analysis is not very reliable for selenium. Until we find reasonably priced testing methods that correlate accurately with tissue levels and health status, it is wise to take additional selenium as outlined here, unless one lives in a selenium-rich area.


Requirements: Like many of the trace minerals, there is no specific RDA for selenium. The usual suggested intake is between 50 and 200 mcg., which is also the range provided by the average diet of wholesome foods and water. Selenium is increasingly available in vitamin-mineral supplements and is part of all nutritional antioxidant formulae.


The conservative safe amount of selenium is between 100-200 mcg. per day for adults and about 30-150 mcg. per day for children, depending on age. Men may need more selenium, especially when sexually active. I usually suggest no more than 200-400 mcg. per day in supplemental form, though some people do take more. Studies have used 1 mg. per day for extended periods without any adverse effects. It is likely that we need more than 100 mcg. daily to support some of selenium’s functions, such as its antioxidant, anticarcinogenic, and immunostimulating effects, though further research is needed to confirm this.


Some of these functions may be best performed with the help of vitamin E; the antioxidant effects of selenium and E are synergistic. There is also a concern that vitamin C may inactivate selenium in the stomach or small intestine. This is not the case with organic selenium, selenocysteine or selenomethione, but it seems that vitamin C combines with sodium selenite and may make the selenium formed by this interaction less absorbable and possibly more toxic. So for improved function, it is wise to take selenium in the absence of vitamin C and along with vitamin E.

Elson M. Haas MD Written by Elson M. Haas MD

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