Selenium is a trace mineral found in soil and food. It is an important antioxidant, which means it helps prevent harmful chemical reactions from occurring in the body's cells. Protected cells are better able to fight off diseases, including heart disease, cancer, and disorders associated with aging.

Most of us do not get enough selenium from food. When our selenium levels are low, we run a higher risk of getting a variety of illnesses because our immune systems may be sluggish and toxins build up in the blood.

If you need to add selenium to your diet, your health care provider will probably suggest that you take a selenium supplement in combination with vitamin E. Research shows that selenium taken together with vitamin E promotes overall health and prevents or treats many diseases.

Selenium cures Keshan disease, a serious heart disorder common to women and children in China, where the farmland lacks minerals. However, results from clinical studies suggest that selenium also protects the body from more common illnesses, including the following:

• Cancer. Selenium reduces your risk of breast, colon, liver, skin, and lung cancers. Selenium keeps tumors from growing by helping to build healthy, cancer-fighting white blood cells.
• Heart disease. Studies show that selenium prevents heart attacks and strokes by lowering your bad (LDL) cholesterol. Selenium also keeps your arteries clear of dangerous fatty deposits, which makes it an important addition to your therapy after a heart attack.
• Weakened immune system. Selenium helps build up white blood cells, boosting your body's ability to fight illness and infection.

Selenium also helps with the following:

• Reproductive health, through increasing male fertility, as well as helping with proper fetal development
• Helps the liver, thyroid, and pancreas function normally
• Prevents premature aging, cataract formation and, possibly, sudden infant death syndrome (SIDS)
• Treats lupus, rheumatoid arthritis, and alcoholic cirrhosis of the liver
• Treats most skin disorders, including poor elasticity, acne, eczema, and psoriasis
• May help in the treatment of depression; it has been reported that a high selenium diet reduced feelings of depression in people with low selenium levels.

• May improve symptoms of diabetes (by returning blood glucose levels to normal range and reduce the risk of associated complications.

Much of your selenium comes from dietary sources. Brewer's yeast and wheat germ, liver, butter, fish and shellfish, garlic, grains, sunflower seeds, and Brazil nuts are all good sources of selenium. It's also found in alfalfa, burdock root, catnip, fennel seed, ginseng, raspberry leaf, and yarrow.

Selenium is destroyed when foods are refined or processed. You should try eating a wide variety of whole, unprocessed foods. This means eating foods in their original state, not canned, frozen, or commercially prepared.

Your health care provider may recommend that you add selenium to your diet. You can do this by taking a vitamin-mineral supplement, a nutritional antioxidant formula, or a separate supplement. Selenium is also available in nutritional yeast.

For best results, selenium should be taken with vitamin E. Ask your healthcare provider to recommend an appropriate dose.

As with all medicines and supplements, check with a healthcare provider before giving selenium supplements to a child.

The minimum daily recommended dietary allowances for selenium are listed below.

Pediatric

• Neonates to 6 months: 10 mcg
• Infants 6 months to 1 year: 15 mcg
• Children 1 to 6 years: 20 mcg
• Children 7 to 10 years: 30 mcg
• Males 11 to 14 years: 40 mcg
• Females 11 to 14 years: 45 mcg

The usual therapeutic dosage for children is considered to be 30 to 150 mcg, or 1.5 mcg per pound (0.7 mcg per kilogram) of body weight.

Adult

• Males 15 to 18 years: 50 mcg
• Males over 19 years: 70 mcg
• Females 15 to 18 years: 50 mcg
• Females over 19 years: 55 mcg
• Pregnant females: 65 mcg
• Lactating females: 75 mcg

Usual therapeutic dosage for adults is considered to be 50 to 200 mcg/day; but as high as 400 mcg/day may be recommended by a healthcare provider.

Selenium is usually not toxic. However, high doses (more than 1,000 mcg a day) over time may produce fatigue, arthritis, hair or fingernail loss, garlicky breath or body odor, gastrointestinal disorders, or irritability. Researchers have also discovered high levels of selenium in children with behavioral problems.

Selenium may reduce toxic side effects associated with cisplatin and doxorubicin, two forms of chemotherapy.

Belch JF, Belch PA. Prescription for Nutritional Healing. 2nd ed. Garden City Park, NY: Avery Publishing Group; 1997:28.

Baldew GS, van den Hamer CJ, Los G, et al. Selenium-induced protection against cis-diamminedichloroplatinum(II) nephrotoxicity in mice and rats. Cancer Res. 1989;49:3020-3023.

Benton D, Cook R. The impact of selenium supplementation on mood. Biol Psychiatry. 1991;29(11):1092-1098.

Boucher F, Coudray C, Tirard V, et al. Oral selenium supplementation in rats reduces cardiac toxicity of adriamycin during ischemia and reperfusion. Nutr. 1995;11(5 Suppl):708-711.

Clark LC, Combs GF Jr, Turnbull BW, et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. JAMA. 1996;276:1957–1963.

Combs GF, Clark LC. Can dietary selenium modify cancer risk? Nutr Rev. 1985;43:325–331.

Dimitrov NV, Hay MB, Siew S, et al. Abrogation of adriamycin-induced cardiotoxicity by selenium in rabbits. Am J Pathol. 1987;126:376-383.

Dworkin BM. Selenium deficiency in HIV infection and the acquired immunodeficiency syndrome (AIDS). Chem Biol Interact. 1994;91:181–186.

Garland M, Morris JS, Stampfer MJ, et al. Prospective study of toenail selenium levels and cancer among women. J Natl Cancer Inst. 1995;8:497–505.

Haas EM. Staying Healthy with Nutrition: The Complete Guide to Diet and Nutritional Medicine. Berkeley, Calif: Celestial Arts; 1992:211–216.

Murray MT. Encyclopedia of Nutritional Supplements: The Essential Guide for Improving Your Health Naturally. Rocklin, Calif: Prima Publishing; 1996:10–13, 222–228.

National Research Council, Diet and Health. Implications for Reducing Chronic Disease Risk. Washington, DC: National Academy Press; 1989:376–379.

Olas B, Wachowicz B. Selenium in the cytotoxicity of cisplatin. Postepy Hig Med Dosw. 1997;51(1):95-108.

Prasad K, ed. Vitamins, Nutrition and Cancer. New York, NY: Karger; 1984.

Sundstrom H, Korpela H, Sajanti E, et al. Supplementation with selenium, vitamin E and their combination in gynaecological cancer during cytotoxic chemotherapy. Carcinog. 1989;10:273-278.

Vermeulen NP, Baldew GS, Los G, et al. Reduction of cisplatin nephrotoxicity by sodium selenite. Lack of interaction at the pharmacokinetic level of both compounds. Drug Metab Dispos. 1993; 21:30-36.

Walker LP, Hodgson Brown E. The Alternative Pharmacy. Paramus, NJ: Prentice Hall Press; 1998:313.

Wasowicz W. Selenium concentration and glutathione peroxidase activity in blood of children with cancer. J Trace Elem Electrolytes Health Dis. 1994;8:53–57.

Werbach MR. Nutritional Influences on Illness: A Sourcebook of Clinical Research. New Canaan, Conn: Keats Publishing; 1988.

Yang GQ, Xia YM. Studies on human dietary requirements and safe range of dietary intakes of selenium in China and their application in the prevention of related endemic diseases. Biomed Environ Sci. 1995;8:187–201.

Yoshizawa K, Willett WC, Morris SJ, et al. Studies of prediagnostic selenium level in toenails and the risk of advanced prostrate cancer. J Natl Cancer Inst. 1998;90:1219–1224.