-IBIS-1.7.6-
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minerals (nutrition)
selenium (Se)
Nutrition
definition
Selenium:
» overview:
An essential mineral found in minute amounts which works closely with vitamin E.
Initially, Selenium was thought to be a toxic element due to diseases which appeared in animals who grazed on land that had high selenium levels. Blind staggers and alkali disease can occur in cattle and sheep.
Scattered findings of selenium deficiencies in humans and animals were reported as far back as 1295 by Marco Polo.
Prior to 1957 symptoms of selenium deficiency were thought to be caused by a vitamin E deficiency.
» metabolism:
Selenium is absorbed fairly easily in the upper GI. Plant sources of selenium may be more bioavailable compared to animal sources. There is some controversy over which form of selenium is more bioavailable. Currently the literature shows that the organic and inorganic forms may have different properties.
Organic forms include selenomethionine, selenocysteine, amino acid chelates, yeast, and kelp bound selenium.
Inorganic forms include sodium selenite and sodium selenate. Some rat studies have shown that the selenite form of selenium raised tissue levels of glutathione peroxidase the most and the organic selenium from tuna was the worst. It seems that certain plant forms of selenium may be the best sources.
Stephen Levine, author of Antioxidant Adaptation: Its role in Free Radical Pathology, recommends using incrementally increasing doses of sodium selenite especially for decreasing sensitivity to environmental toxins. Some people can not tolerate high doses of selenium and this method may work.
Selenocysteine is the form in which selenium is incorporated into the glutathione peroxidase molecule. There is a specific genetic code that requires insertion of selenocysteine into certain proteins used in the synthesis of glutathione peroxidase. Selenium may thus regulate the transcription of glutathione peroxidase. It is known that selenium supplementation will increase glutathione levels in the liver of a person who is deficient in selenium. (Marz, p. 137, 1997)
» Chinese:
Benefits the Yin; restrains Floating Yang; settles and calms the Shen (Spirit); astringes the Jing (Essence); brightens the eyes; removes superficial visual obstruction.
» function:
Selenium is involved in the synthesis of the enzyme glutathione peroxidase. It consists of a 4 subunit enzyme with one selenium per subunit in the form of selenocysteine. This enzyme is responsible for detoxification in the body.
Converts HPETE (hydroperoxyeicosatetraenoic acid) into HETE (hydroxyeicosatetraenoic acid)
HPETE -> glutathione peroxidase -> HETE
Selenium may be an important inhibitor of various types of cancer.
Natural antioxidant
Necessary for production of prostaglandins
With vitamin E helps promote normal growth and development
» requirements:
RDA: 55-70 mcg
Optimal Daily Intake: 200-300 mcg per day, depending upon toxin exposure.
Average intake in the U.S.: 100 mcg per day.
» food sources:
It should be noted that selenium quantities vary in foods depending upon the levels in the soil. Many agricultural areas are extremely deficient in selenium. Grains are generally a good source. Garlic and mushrooms are sometimes quite high in selenium. Asparagus is a good source of selenium, but other fruits and vegetables are poor sources.
Best Food Sources of Selenium:
Food Amount mg.
Brazil nuts 114 cup 380
Snapper, baked 3 oz 148
Halibut, baked 3 oz 113
Salmon 3 oz 70
Scallops, steamed 3 oz 70
Swiss chard 1 cup 57
Clams, steamed 20 52
Oats 3 oz 50
Orange juice 1 cup 50
Oysters 1/4 cup 35
Wheat germ 1/4 cup 35
Molasses, black strap 2 Tbsp 25
Sunflower seeds 25 25
Granola 1 cup 23
Bread, whole wheat 1 slice 20
Rice, brown 1 cup 20
Turnips, cooked 1 cup 18
Barley, uncooked 1 cup 12
Garlic 3 cloves 2~5
(USDA: Composition of Foods. USDA Handbook # 8. Washington DC, ARS, USDA, 1976-1986)
» deficiency:
Keshan disease: Cardiomyopathy develops in children and young women in a certain area of China where soil selenium is deficient. This condition is reversible upon selenium supplementation. It has been postulated that this condition might be due to a viral condition that only manifests itself when there is a deficiency of selenium.
Kashin-Beck disease: This is an arthritis condition that develops also where there are low levels of selenium in the soil.
Duchennes muscular dystrophy is also associated with increased selenium excretion.
There are other diseases in which ceroid pigment granules accumulate in nervous tissue. Other symptoms may include anemia, growth retardation, painful muscles. In Finland there has been shown to be an extreme selenium deficiency in the soil. This may be a link to the high incidence of cardiovascular disease. A double blinded trial of Vitamin E and Selenium in Finland found that higher levels of these two nutrients were associated with improved mental, emotional, and physical parameters of well-being. (Marz, p. 138, 1997)
» therapeutics:
Allergies, Detoxification and Immunity: 200-800 mcg per day. Steven Levine from the Allergy Research Group has a protocol for allergy desensitization. Some studies have shown selenium supplementation of 200mcg may increase levels of white blood cells and thymus activity.
Arthritis and other inflammatory conditions require increased amounts of antioxidant nutrients. Selenium is a major antioxidant.
Cancer prevention: 200-800 mcg per day. Selenium acts to detoxify many bodily toxins via the enzyme glutathione peroxidase. Low levels of soil selenium have been linked to increases in various forms of cancer in the U.S. and Finland. Selenium seems to exert its highest protection against lung and intestinal cancers. Selenium may be used as an adjunct therapy in the treatment of cancer.
Cardiovascular Disease: Like cancer, there is an association with higher incidence of heart disease where there are lower levels of selenium in the soil, although the relationship is not quite as strong. Selenium acts by protecting endothelial cells of the arteries against oxidative damage.
Cataracts and macular degeneration: Studies using both IV or oral selenium supplementation have shown it to be helpful in the treatment of these conditions.
(Swanson A, Truesdale A. Biochem Biophys Res Comm 45, 1488-96, 1971; Karakucuk S, et al. Archiv Ophthamolgy Scand 73, 329-32, 1995)
Cystic Fibrosis: Joel Wallach has pioneered the use of selenium and vitamin E in the treatment of this condition with reported success.
Heavy metal toxicity: Selenium, being involved with glutathione peroxidase, is critical for the protection of the liver.
Hepatitis C: In a small clinical trial based on three cases treated with an anti-oxidant triad of silymarin, alpha lipoic acid and selenium, Berkson reported a significant postive response.
(Berkson BM. Med Klin. 1999 Oct 15;94 Suppl 3:84-89. )
Myotonic dystrophy and other forms of dystrophy.
Osgood-Schlatter and growing pains respond to 200-400 mcg per day selenium and 400-800 IU per day vitamin E.
Viral illness, prevention and treatment of viral illness especially retroviruses.
(Hou, J.C., et al. Chung-Hua-I-Hsueh-Tsa-Chih 73, (11) a645-6, 699, 1993).
Prostate Cancer: One study involving 974 men, with a history of skin cancer, who took 200 mcg daily (in the form of selenium-rich yeast tablets) for 4-5 years found a 63% reduction in their risk of prostate cancer for 6.5 years after they stopped the supplementation.
(Clark LC, et al. Br J Urol 1998 May;81(5):730-734.)
SIDS: It has been found that selenium levels become depleted at the end of pregnancy. This may explain why there is a problem with toxemia toward the end of pregnancy. (Marz, p. 139, 1997)
» drug-related therapeutics:
Chemotherapy protection: Along with other antioxidant nutrients, selenium is a critical nutrient for the protection of cells thoughout the body.
» dosage:
Maintenance dose: 200 mcg per day.
Therapeutic dose: 200-800 mcg per day.
» toxicity:
800 mcg per day is probably the highest long term daily dose that can be taken without the development of toxicity in most people. There are variations in the toxic dose, as with other nutrients, but selenium must be used with caution. Estimates from cattle and other animals show that the toxic long term dose is probably closer to 2.4-3 mg per day. This would lead to symptoms such as liver, skeletal and cardiac muscle damage.
Selenium has a narrow margin of safety.
Toxic signs may also include garlic breath and sweat, metallic taste in mouth, depression, nervousness, emotional instability, nausea, vomiting, weight loss, hair loss, finger nail damage, and digestive irritation.
Signs and symptoms of toxicity include: loss of hair, teeth, nails; dermatitis; lethargy; and paralysis; severe overdose: fever, increased respiratory rate, gastrointestinal distress, myelitis, and if extreme, death.
» interactions:
Selenium generally has a synergistic relationship with the other antioxidant nutrients.
It appears to lose some of its normal function when exposed to lead, mercury, cadmium, and arsenic.
Chronic exposure to environmental toxins, including chemotherapeutic drugs, radiation and other toxic medications, increase its requirement, since selenium is used in the generation of glutathione peroxidase, an enzyme used in the detoxification process.
footnotes
Berkson BM. A conservative triple antioxidant approach to the treatment of hepatitis C. Combination of alpha lipoic acid (thioctic acid), silymarin, and selenium: three case histories. Med Klin. 1999 Oct 15;94 Suppl 3:84-89.
Abstract: BACKGROUND: There has been an increase in the number of adults seeking liver transplantation for hepatitis C in the last few years and the count is going up rapidly. There is no reliable and effective therapy for chronic hepatitis C since interferon and antivirals work no more than 30% of the time, and liver transplant surgery is uncertain and tentative over the long run. This is because, ultimately, residual hepatitis C viremia infects the new liver. Furthermore, liver transplantation can be painful, disabling and extremely costly. TREATMENT PROGRAM: The author describes a low cost and efficacious treatment program in 3 patients with cirrhosis, portal hypertension and esophageal varices secondary to chronic hepatitis C infection. This effective and conservative regimen combines 3 potent antioxidants (alpha-lipoic acid [thioctic acid], silymarin, and selenium) that possess antiviral, free radical quenching and immune boosting qualities. CONCLUSION: There are no remarkably effective treatments for chronic hepatitis C in general use. Interferon and antivirals have less than a 30% response rate and because of the residual viremia, a newly transplanted liver usually becomes infected again. The triple antioxidant combinaton of alpha-lipoic acid, silymarin and selenium was chosen for a conservative treatment of hepatitis C because these substances protect the liver from free radical damage, increase the levels of other fundamental antioxidants, and interfere with viral proliferation. The 3 patients presented in this paper followed the triple antioxidant program and recovered quickly and their laboratory values remarkably improved. Furthermore, liver transplantation was avoided and the patients are back at work, carrying out their normal activities, and feeling healthy. The author offers a more conservative approach to the treatment of hepatitis C, that is exceedingly less expensive. One year of the triple antioxidant therapy described in this paper costs less than $2,000, as compared to more than $300,000 a year for liver transplant surgery. It appears reasonable, that prior to liver transplant surgery evaluation, or during the transplant evaluation process, the conservative triple antioxidant treatment approach should be considered. If these is a significant betterment in the patient's condition, liver transplant surgery may be avoided.
Clark LC, Dalkin B, Krongrad A, Combs GF Jr, Turnbull BW, Slate EH, Witherington R, Herlong JH, Janosko E, Carpenter D, Borosso C, Falk S, Rounder J. Decreased incidence of prostate cancer with selenium supplementation: results of a double-blind cancer prevention trial. Br J Urol 1998 May;81(5):730-734.
Abstract: OBJECTIVE: To test if supplemental dietary selenium is associated with changes in the incidence of prostate cancer. PATIENTS AND METHOD: A total of 974 men with a history of either a basal cell or squamous cell carcinoma were randomized to either a daily supplement of 200 microg of selenium or a placebo. Patients were treated for a mean of 4.5 years and followed for a mean of 6.5 years. RESULTS: Selenium treatment was associated with a significant (63%) reduction in the secondary endpoint of prostate cancer incidence during 1983-93. There were 13 prostate cancer cases in the selenium-treated group and 35 cases in the placebo group (relative risk, RR=0.37, P=0.002). Restricting the analysis to the 843 patients with initially normal levels of prostate-specific antigen (< or = 4 ng/mL), only four cases were diagnosed in the selenium-treated group and 16 cases were diagnosed in the placebo group after a 2 year treatment lag, (RR=0.26 P=0.009). There were significant health benefits also for the other secondary endpoints of total cancer mortality, and the incidence of total, lung and colorectal cancer. There was no significant change in incidence for the primary endpoints of basal and squamous cell carcinoma of the skin. In light of these results, the 'blinded' phase of this trial was stopped early. CONCLUSIONS: Although selenium shows no protective effects against the primary endpoint of squamous and basal cell carcinomas of the skin, the selenium-treated group had substantial reductions in the incidence of prostate cancer, and total cancer incidence and mortality that demand further evaluation in well-controlled prevention trials.
Hou, J.C., et al. Inhibitory effect of selenium on complement activation and its clinical significance. Chung-Hua-I-Hsueh-Tsa-Chih 73, (11) a645-6, 699, 1993.
Abstract: Sodium selenite inhibited hemolysis induced by complement activation in-vivo in mice. 80 patients with epidemic hemorrhagic fever received multiple dosages of 2 mg selenite per day during the 1st 9 days of hospitalization. In fulminant cases mortality fell from 100% in the untreated patients to 36% in those receiving selenium. In severe cases mortality fell from 22% in untreated cases to zero in those receiving selenium.
Karakucuk, S., et al. Selenium concentrations. in serum, lens, and aqueous humour of ptatiens with senile cataract. Archiv Ophthamolgy Scand 73, 329-32, 1995.
Abstract: It was found that there was a 25 times greater concentration of hydrogen peroxide levels compared to normals.
Swanson, A., and Truesdale, A. Elemental analysis in normal and cataract human lens tissue. Biochem Biophys Res Comm 45, 1488-96, 1971.
Abstract: It was found that people who had developed cataracts had 85% less selenium than controls concentration in the lens.