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
Selenium occurs most commonly in nature as inorganic sodium selenite. Other,
more absorbable and active forms include selenomethione or selenocysteine and
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
- 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
- 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
|Dosage Ranges and Duration of
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.
Balch JF, Balch 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.
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.
Combs GF, Clark LC. Can dietary selenium modify cancer risk? Nutr Rev.
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.
Garland M, Morris JS, Stampfer MJ, et al. Prospective study of toenail
selenium levels and cancer among women. J Natl Cancer Inst.
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;
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Chronic Disease Risk. Washington, DC: National Academy Press;
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;
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.
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