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Selenium supplements |
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Selenium is an essential trace mineral that is a component of majoy antioxidant enzymes, selenoproteins (glutathione peroxidase, thioredoxin reductase). Glutathione peroxidase is responsible for detoxification in the body by reducing peroxide free radicals that include lipid peroxide formation in cell membranes. Reduction of peroxides formed by oxidation of membrane phospholipids breaks the auto-oxidative chain reaction that damages cell membranes. L-selenomethionine is, an organic form of selenium, accumulates in the body because it is incorporated into proteins in place of the amino acid methionine. It is stored in the body and is slowly released. The body uses the nutrient selenium provided by l-selenomethionine to make antioxidant proteins, such as glutathione peroxidase and thioredexin reductase, which protect against cancer-causing free radicals. A byproduct of l-selenomethionine, methylselenol, is probably the anti-cancer form of selenium. Selenium is also essential for normal functioning of the immune system and thyroid gland. Selenium is stored in the tissues in varying density: 30 percent of tissue selenium is in the liver, 15 percent in the kidney, 30 percent in muscle, 10 percent in the plasma, and the remaining 15 percent throughout other organs. Dietary selenium comes from cereals, meat, fish, and eggs. Brazil nuts are a particularly rich source of selenium.
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Biological functions and health benefits of selenium |
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| Selenium is incorporated into proteins to make selenoproteins, which are important antioxidant enzymes. At least 25 selenoproteins have been identified in human biochemistry. The major selenoproteins include glutathione peroxidases,
iodothyronine deiodinases, thioredoxin reductases, selenoprotein P, selenoprotein W and selenophosphate synthetase. Glutathione peroxidase neutralizes hydrogen peroxide, which is produced by some cell processes and would otherwise damage cell membranes. Thioredoxin reductase, another selenoenzyme that acts as an antioxidant, is responsible for degrading peroxides and hydroperoxides outside cell membranes. Peroxides and hydroperoxides have been shown to cause cell death, DNA damage, and tissue atrophy. Thioredoxin reductase also recycles lipoic acid and vitamin C, regulates the metabolism of vitamin K3, and acts to regulate cell growth and the activity of tumor-suppressing protein p53.
Selenium along with other minerals can help build up white blood cells, enhancing the body's ability to fight illness and infection. The antioxidant properties of selenoproteins help prevent cellular damage from free radicals. Selenium contributes to the normal functioning of the immune system and the thyroid gland. Free radicals are natural by-products of oxygen metabolism that may contribute to the development of chronic diseases such as cancer and heart disease. Selenium helps repair cells in the lungs and other organs damaged by oxidative stress, promotes healthy immune system function, and protects red blood cells and cell membranes. Selenium may help prevent the two most common causes of impaired vision and blindness in older people, cataracts and macular degeneration, by providing antioxidant actions that fight free radicals.
Selenium may assist in the synthesis of protein, in growth and development, and in fertility, especially in men. Selenium and other antioxidants play an essential role in the formation of certain proteins found in sperm. It has been shown to improve the production of sperm and sperm motility. Selenium also acts as an anti-inflammatory agent in the treatments of arthritis and other autoimmune diseases. Selenium inhibits prostaglandins, which cause inflammatory reactions in the body. Selenium's antioxidant and anti-inflammatory actions may be enhanced when combined with vitamin E. It is being used to treat a condition called Kashin-Beck disease, which affects the joints.
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Selenium deficiency |
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| Selenium deficiency in healthy people is relatively rare. However, it can occur in patients with severely compromised intestinal function, or those undergoing total parenteral nutrition. Alternatively, people dependent on food that is sourced from selenium-deficient soil are also at risk. Severe gastrointestinal disorders may decrease the absorption of selenium, resulting in selenium depletion or deficiency. People with selenium deficiency have a greater chance of developing cancer, heart disease, inflammatory disease, cataracts, and signs of premature aging. Lack of selenium may lead to changes in fingernails, muscle weakness, and heart problems. Low blood levels of selenium can contribute to heart failure. Selenium deficiency may worsen atherosclerosis and can lead to premature aging. People with asthma tend to have low blood levels of selenium. Cigarette smokers have lower levels of selenium. People with inflammatory bowel disease often have reduced levels of selenium, as well as other vitamins and minerals, in their bodies. Low selenium levels may be associated with an increased risk for liver cancer in people with hepatitis B and/or C. Low levels of selenium in the blood may be associated with increased risk of rheumatoid arthritis. Keshan disease is caused by a deficiency of selenium. This leads to an abnormality of the heart muscle. Keshan disease claimed the lives of many children in China until the relationship to selenium was discovered and selenium supplements were provided. |
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Dietary sources of selenium |
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Plant foods are the major dietary sources of selenium in most countries throughout the world. The amount of selenium contained in different foods depends upon the level of selenium in the soil. Brazil nuts are the best source of selenium. Fish, shellfish, red meat, grains, eggs, chicken, liver, and garlic are all good sources of selenium. Brewer's yeast and wheat germ, both considered "health foods," are also good sources of selenium. Selenium may be taken as part of a vitamin-mineral supplement, a nutritional antioxidant formula, or as an individual supplement. Available selenium supplements include high-selenium yeast, L-selenomethionine, sodium selenate and sodium selenite.
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Dosage, intake, recommended daily allowance (RDA) |
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The recommended dietary allowance for adults is 55 mcg for women and 70 mcg for men. For infants and children, the RDA usually ranges from 10 to 30 mcg per day. Specific recommendations for each nutrient depend on age, gender, and other factors (such as pregnancy).
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Side effects, precautions, toxicity, and drug interactions |
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Selenium can be toxic at very high doses. High blood levels of selenium can result in a condition called selenosis. Symptoms include gastrointestinal upsets, hair loss, white blotchy nails, and mild nerve damage. The Institute of Medicine has set a tolerable upper intake level for selenium at 400 micrograms per day for adults to prevent the risk of developing selenosis.
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Selenium Food Complex contains minerals that help in normal cell growth and detoxification. Each tablet is filled with highly active probiotic selenium that is up to 64 times more active than in its purified form. They contain cultured herbs like cinnamon, oregano, and rosemary that are known for their ability to counter oxidation safely, and nutrients that have cell protective and antioxidant effects. Click here for more information.