Selenium is a trace mineral and an important part of the enzyme glutathione peroxidase. It is an effective antioxidant, especially when combined with vitamin E. Working as part of this enzyme, selenium or, more specifically, the organic complex selenocysteine, helps protect intracellular structures by preventing the formation of damaging free radicals. Like other antioxidant supplements, selenium slows chemical aging and helps maintain elasticity of bodily tissues, organs, and the cardiovascular system.

Extreme selenium deficiency can lead to a rare heart disorder known as Keshan disease, which results in congestive heart failure and is most evident in parts of China where soil-selenium levels are low. More commonly, though, selenium deficiency is indicated in high rates of cancer, heart disease, and immunodepression. Selenium is frequently lacking in Western diets, again due to mineral-poor farmland. Typical consumption in the U.S. is estimated at 100 mcg/day. Many of selenium's antioxidant and anticarcinogenic functions require much greater augmentation (>200 mcg/day).

Numerous animal and human studies conclude that fortifying the diet with added selenium, vitamin E, and other vital antioxidants boosts the immune system by stimulating white blood cell development and thymus function. In this way, selenium significantly challenges cancerous tumor incidence and development, and contributes to myriad other immune system benefits. Conversely, research finds low levels of selenium and glutathione peroxidase in cancer patients.

Selenium also plays a crucial role in preventing or managing coronary heart disease, stroke, and cardiovascular disease both before and after heart attacks, especially for patients who smoke, due to its antioxidant mechanisms and its role in lowering LDL cholesterol levels. Selenium also appears to inhibit platelet aggregation, increasing its significance in cardiovascular health.

Other studies have determined that selenium improves liver and metabolic function, even in extreme cases of alcoholic cirrhosis of the liver, and enhances pancreatic function. Additionally, sufficient selenium intake has been indicated in prostate health and sperm motility, plays a prominent role in skin health and elasticity, and protects against cataract formation. Selenium acts as an antagonist to heavy metals.

Brewer's yeast and wheat germ, liver, butter, fish and shellfish, garlic, grains, sunflower seeds, and Brazil nuts are all food sources for naturally occurring selenium. Herbal sources include alfalfa, burdock root, catnip, fennel seed, ginseng, raspberry leaf, and yarrow.

The amount of selenium in foodstuffs corresponds directly to selenium levels in soil. Deficiencies are noted in parts of China and the U.S. where soil-selenium ratios are low.

Food-source selenium is destroyed during processing. Therefore, a varied diet of whole foods is recommended. (Whole foods are those eaten in their original form, rather than canned, frozen, or otherwise commercially processed or prepared.)

Selenium occurs most commonly in nature as inorganic sodium selenite. Other, more absorbable and active forms include selenomethione or selenocysteine and selenium-rich yeast.

Selenium is available as part of many vitamin-mineral supplements, all nutritional antioxidant formulas, and, increasingly, as an independent supplement. Suggested intake is between 50 and 200 mcg per day for adults. Men apparently require more than women, because stores are lost with ejaculation. Selenium should be taken with vitamin E, as the two act synergistically, and without vitamin C, which decreases absorbability and is likely to increase risk of selenium toxicity.

Clinical trials suggest that supplemental selenium well beyond daily dietary intake (>100 mcg) is necessary to support at least some of the following functions. Selenium deficiency is most evident in a positive response to supplemental selenium therapy. Blood and urinary levels are inadequate indicators of selenium intake and tissue levels.

• Cancer. Acts as an anticancer antioxidant, protecting against or reducing the incidence of breast, colon, liver, skin, and respiratory tumors and cancers.
• Heart disease. Prevents and manages coronary heart disease, cardiovascular disease, and stroke by helping to lower LDL cholesterol and reduce platelet aggregation. Reduces post–heart attack mortality. Successful in treatment of Keshan disease.
• Immunodepression. Boosts immune function and white blood cell development. Suggested in the treatment of depressed immune disorders such as lupus. Contributes to the bactericidal action of phagocytes. Counters heavy metal toxicity such as lead, mercury, and cadmium poisoning. Stimulates antibody formation in response to vaccinations.
• Liver disease. Effective against alcohol-induced cirrhosis of the liver and alcoholic cardiomyopathy. Promotes proper liver and metabolic function.
• Skin disorders. Indicated for treatment of acne, eczema, psoriasis, vasculitis, and other skin disorders. Responds to vitamin E deficiencies in combination with vitamin E supplementation. Prevents premature aging.
• Muscular and inflammatory illness. Effective in treating all major symptoms of myotonic dystrophy. Suggested in the treatment of inflammatory conditions such as rheumatoid arthritis.
• Eyesight. Required for the antioxidant protection of the lens; helps prevent cataract formation.
• Reproductive health. May assist in male fertility, prostate function, and sperm motility.
• Promotes healthy fetal development and may help in prevention of SIDS.

A minimum RDA for selenium is as follows.

• 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
• Males 15 to 18 years: 50 mcg
• Males over 19 years: 70 mcg
• Females 11 to 14 years: 45 mcg
• Females 15 to 18 years: 50 mcg
• Females over 19 years: 55 mcg
• Pregnant females: 65 mcg
• Lactating females: 75 mcg
• Usual dosage for children: 30 to 150 mcg or 1.5 mcg per pound of body weight. For adults: 50 to 200 mcg/day.

Long-term ingestion of excessive levels of selenium (>1,000 mcg/day) may produce fatigue, depression, arthritis, hair or fingernail loss, garlicky breath or body odor, gastrointestinal disorders, or irritability. Such high intakes and chronic toxicity are rare.

Studies found high hair selenium levels in children with learning disabilities and behavioral problems. Extremely high doses may cause cumulatively toxic effects over time.

Selenium may reduce side effects from cisplatin without reducing the clinical effectiveness of this medication (Olas and Wachowicz 1997). Administration of sodium selenite (2 mg/kg) one hour before cisplatin treatment greatly reduced the nephrotoxic effects associated with the drug but did not alter antitumor activity (Baldew et al. 1989). The pharmacokinetic parameters of the drug were also not affected by the combination of radiolabeled sodium selenite and cisplatin (Vermeulen et al. 1993).

A clinical trial involving 41 patients with ovarian or metastatic endometrial cancer evaluated the effects of selenium on various cancer treatments (Sundstrom et al. 1989). Patients were treated with cisplatin in combination with either doxorubicin and cyclophosphamide or melphalan. In addition, some patients were supplemented with selenium (200 mcg/day sodium selenate), vitamin E (300 mg/day), or selenium and vitamin E. Selenium supplementation during cisplatin treatment reduced measures of oxidative stress.

Preclinical studies also suggest that selenium supplementation limits doxorubicin-induced cardiotoxicity (Boucher et al. 1995; Dimitrov et al. 1987). Selenium was more effective when given prior to doxorubicin exposure.

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