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Selenium

 

Natural Standard Monograph, Copyright © 2014 (www.naturalstandard.com). Commercial distribution prohibited. This monograph is intended for informational purposes only, and should not be interpreted as specific medical advice. You should consult with a qualified health care professional before making decisions about therapies and/or health conditions.

Related Terms

  • 5-methylselenocysteine MSC, adrusen zinco, atomic number 34, DL-selenomethionine, benzisoselenazol, ebselen, gamma-glutamyl-selenomethyl-SeCys, high-selenium yeast, L-selenomethionine, methylseleninic acid, methyl selenol, monomethylated Se, Na2SeO3, parselenium, Se, Se-EMP, Sele-Pak, selepen, Se-malt, SeMCYS, Seme, SeMet, Se-methylselenocysteine, SeO3(2-), SeO4(2-), SeS, Se-yeast, selen, selenium dioxide, selenium sulfide, seleno yeast, selenocysteine, selenomethionine, selenate, selenious acid, selenite, selenite-exchangeable metabolic pool, selenium dioxide, selenium disulfide, selenium sulfide, selenium-enriched wheat, selenium-enriched yeast, selenium-rich pea flour, selenium-zinc, selenized yeast, seleno yeast, selenocysteine, selenoenzymes, seleno-L-methionine, selenomethionine, selenomethyl-SeCys, selenoprotein P, selenoproteins, selenous acid, selepen, Selmevit, Semet, se-spirulina, se-yeast, SLM, sodium selenate, sodium selenite, Spirulin-Sochi-Selen, wheat selenium.

Background

  • Selenium is an essential trace mineral found in soil, water, and some foods. Selenium is required for functioning of the body's antioxidant enzymes and for cell growth and survival.
  • The presence of selenium in locally grown food and selenium levels in human populations reflects the selenium levels in local soil. The selenium content in food is influenced by geographical location, seasonal changes, protein content, and food processing. Periodic monitoring of selenium levels in soil and food is necessary. Selenium supplements may benefit people living in regions with very low environmental levels of selenium.
  • Selenium has a strong protective action against the poisonous effects of many heavy metals, some toxic compounds, and fungal toxins.
  • The role of selenium in cancer prevention has been the subject of recent study and debate. Initial evidence from the Nutritional Prevention of Cancer (NPC) trial suggested that selenium supplementation reduced the risk of prostate cancer among men with normal baseline PSA (prostate specific antigen) levels and low selenium blood levels. However, in this study, selenium did not reduce the risk of lung, colorectal, or basal cell carcinoma of the skin and actually increased the risk of squamous cell skin carcinoma.

Evidence

 

Uses based on scientific evidence 

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare professional.

Grade* 

Antioxidant 

Selenium is a component of the enzyme glutathione peroxidase, which has antioxidant properties in humans. Further research is needed.

B 

Keshan disease 

Keshan disease affects heart muscle in people with extremely low selenium status. Preventative administration of sodium selenite, a form of selenium, was shown to reverse heart failure due to selenium deficiency. Although initial results are promising, more high quality studies are needed.

B 

Prostate cancer prevention 

Initial evidence suggested that selenium supplementation may reduce the risk of developing prostate cancer in men with normal baseline PSA (prostate specific antigen) levels and low selenium blood levels. Additional study showed an apparent lack of benefit, however. Further research is required before firm conclusions can be made.

B 

Amyotrophic lateral sclerosis (ALS) 

Studies have consistently reported that antioxidants lack benefit in treating motor neuron diseases such as amyotrophic lateral sclerosis (ALS). High quality research is needed before firm conclusions can be made.

C 

Asthma 

Preliminary research suggests that selenium supplementation, alone or in combination with other vitamins and minerals, may help reduce asthma symptoms. Further research is needed before a conclusion can be made.

C 

Blood disorders 

Selenium supplementation lacked benefit in patients with glucose-6-phosphate dehydrogenase (G-6-PD) deficiency. Selenium supplementation may also affect platelet function and blood clotting.

C 

Cancer prevention 

Initial study suggests that low body levels of selenium may be a risk factor for developing cancer, particularly gastrointestinal, gynecological, lung, colorectal, and esophageal cancer. Studies have shown significantly reduced risk of some (but not all) cancers in people taking selenium supplements. Additional research is needed to determine the precise role of selenium in reducing cancer risk.

C 

Cancer treatment 

Preliminary study suggests that low body levels of selenium may be a risk factor for developing cancer, particularly prostate, gastrointestinal, gynecological, and colorectal cancer. Population studies reported that people with cancer are more likely to have low selenium levels than healthy individuals, but in most cases it is not clear if the low selenium levels are a cause or an effect of the cancer. It remains unclear if selenium is beneficial for treating any type of cancer.

C 

Cardiovascular disease (prevention) 

Studies of the effects of selenium intake and supplementation on cardiovascular disease yield inconsistent findings. Better-designed trials are needed before a conclusion can be made.

C 

Chemotherapy side effects 

Study results of selenium supplementation (usually in combination with other nutrients) during chemotherapy are mixed. Antioxidants may interfere with radiation therapy or some chemotherapy agents, which themselves may depend on oxidative damage to tumor cells for their anti-cancer activity. Further research is needed before a conclusion can be made.

C 

Colitis (inflammation of the large intestine) 

Selenium in combination with fish oil, fructooligosaccharides, gum arabic, vitamin E, and vitamin C has shown some benefit in reducing inflammation associated with ulcerative colitis. Studies testing selenium alone are needed before a conclusion can be made.

C 

Critical illness 

Limited study has tested the effect of selenium on improving health or decreasing mortality in critically ill patients. Results are inconsistent. More research is required before firm conclusions can be made.

C 

Cystic fibrosis 

Preliminary research on the effect of selenium supplementation in cystic fibrosis patients yields indeterminate results. Further research is needed in this area.

C 

Dandruff 

Selenium sulfide may help improve dandruff. Selenium is included in some commercially available shampoos. More research is needed.

C 

Dialysis 

The benefits of selenium supplementation in dialysis patients remain unclear. Some methods of dialysis may lower plasma selenium levels. More well-designed trials are needed before a conclusion can be made.

C 

Eye disorders 

Although people with relatively high dietary intake of selenium have reduced risk of certain eye disorders, the effect of selenium supplements on the risk of developing these disorders is unknown. More research in this area is needed.

C 

Fatigue (associated with primary biliary cirrhosis) 

Antioxidant supplementation, including selenium, has been studied for treating fatigue associated with biliary cirrhosis. Evidence of benefit is inconclusive. More research is needed.

C 

Heavy metal/lead toxicity 

Zinc and selenium have been shown to exert protective effects against mercury toxicity. More research is needed before a conclusion can be drawn.

C 

High blood pressure 

Some studies have reported a possible relationship between low serum selenium levels and increased blood pressure. Additional study is needed in this area.

C 

HIV/AIDS 

Some reports associate low selenium levels in HIV/AIDS patients with complications such as cardiomyopathy. It remains unclear if selenium supplementation is beneficial in patients with HIV, particularly during antiretroviral therapy.

C 

Immune stimulation 

Selenium may help prevent infection by stimulating immune function. Further research is needed before a conclusion can be made.

C 

Infection prevention 

Preliminary research reports that selenium may reduce recurrence of some bacterial infections of the skin or blood, or bacterial pneumonia. Selenium may help prevent infection by stimulating immune function. Further research is needed before a conclusion can be made.

C 

Infertility 

Selenium supplementation has been studied for male infertility and sperm motility with mixed results. Evidence is lacking regarding the potential effects on female infertility. Additional study is needed.

C 

Intracranial pressure symptoms 

Preliminary research shows a decrease in symptoms of elevated intracranial pressure (headaches, nausea, vomiting, vertigo, unsteady gait, speech disorders, and seizures) with selenium supplementation together with other therapies. More research on the effect of selenium alone is needed before a conclusion can be made.

C 

Liver disease 

Selenium supplementation has been studied in various liver disorders, including hepatitis, cirrhosis, and liver cancer, with mixed results. More study is needed.

C 

Longevity/anti-aging 

Because antioxidant supplements are thought to slow aging and prevent disease, it has been proposed that selenium supplementation may help people live longer. However, results from clinical trials are mixed, and it is still unclear whether selenium supplementation can increase lifespan in healthy individuals.

C 

Low birth weight 

Selenium supplementation has been studied in low birth weight infants. Additional study is needed before a clear conclusion can be drawn.

C 

Malabsorption 

Low selenium status has been demonstrated in several malabsorptive syndromes and in some digestive and gastrointestinal allergic conditions. There is some evidence that children with food allergies have a higher risk of selenium deficiency. Further research is needed in this area.

C 

Nutritional support 

Selenium supplementation has been shown to be effective in increasing and maintaining selenium levels in various populations, including breastfeeding mothers and patients with advanced kidney disease. Additional studies are needed before a conclusion can be made.

C 

Pancreatitis 

Selenium together with probiotics and prebiotics may help patients with acute pancreatitis. There is inconclusive evidence regarding the use of selenium alone in pancreatitis. More research is needed.

C 

Physical endurance 

Available evidence suggests that selenium supplementation lacks effect on physical performance or endurance training. Additional studies are needed.

C 

Post-operative recovery 

In limited study, selenium aided postoperative recovery and reduced swelling after surgery. Patients with severe inflammation resulting from surgeries or extensive burns may benefit from selenium therapy. More studies are needed to determine whether selenium is a suitable addition to post-operative therapy and care.

C 

Pregnancy-related complications 

Preliminary study in women with pregnancy-induced high blood pressure reported reduced swelling with selenium supplementation, without a significant impact on birth outcomes. Additional well-designed research is needed.

C 

Quality of life 

Studies of selenium supplementation for mood elevation and quality of life yield mixed results. Further research is needed before a firm conclusion may be reached.

C 

Radiation side effects 

Selenium supplementation has been used as an adjunct therapy to treat radiation side effects. Additional research is necessary before a clear conclusion can be made.

C 

Respiratory tract infections 

Some evidence indicates that selenium may promote recovery from bronchitis and pneumonia caused by respiratory syncytial virus (RSV). Though supplemental selenium may correct selenium deficiency in patients with bronchitis, more studies are needed to examine its effectiveness in treating respiratory infections.

C 

Rheumatoid arthritis 

Selenium supplementation has been studied in rheumatoid arthritis patients with mixed results. Additional research is necessary before a clear conclusion can be made.

C 

Seizures 

It is unclear whether serum selenium levels are related to seizures in patients with epilepsy or brain tumors. More research is needed to examine whether selenium supplementation may affect the frequency or severity of seizures.

C 

Sepsis (severe bacterial infection of the blood) 

Study results of selenium supplementation in septic patients are mixed. Research using selenium alone is needed.

C 

Sunburn prevention 

Sun protection was initially observed in preliminary research using selenium supplementation and other antioxidants, although there is some evidence of ineffectiveness in preventing light-induced skin redness. More studies are needed.

C 

Thyroid conditions 

Thyroid function is thought to depend on selenium, and thyroid problems are common in patients with selenium deficiency. Selenium has been suggested to improve goiter, as well as inflammatory activity in chronic autoimmune thyroiditis or Grave's disease. Further research is needed.

C 

Yeast infections 

Commercially available 1% selenium sulfide shampoo has been reported as equivalent to antifungal therapy for treatment of several types of fungal infections. Further high quality evidence is needed.

C 

Diabetes (prevention) 

Some studies have suggested that selenium supplementation may help prevent type 2 diabetes by improving glucose metabolism. However, other data showed increased rates of type 2 diabetes in people taking selenium supplements. These results indicate a potential risk of selenium supplementation that needs further examination.

D 

Kashin-beck osteoarthropathy 

Kashin-Beck disease is an osteoarthropathy common in selenium- and iodine-deficient areas. Preliminary evidence suggests that selenium supplementation lacks effectiveness.

D 

Muscle and joint disorders 

Selenium and vitamin supplementation has been studied in patients with Duchenne muscular dystrophy (DMD), myotonic dystrophy, and exercise-induced muscle injury. However, selenium does not appear to improve muscle strength or motor performance in patients with myotonic dystrophy. Despite promising early evidence, selenium supplementation does not appear to affect muscle strength or disease progression in muscular dystrophy.

D 

Osteoarthritis 

Selenium-ACE, a formulation containing selenium with three vitamins, has been promoted for the treatment of arthritis. Research has failed to demonstrate significant benefits and there may be more side effects compared to placebo.

D 

Skin cancer (nonmelanoma) prevention 

Results of a large study suggested that selenium supplementation given to individuals at high risk of nonmelanoma skin cancer is ineffective at preventing basal cell carcinoma and actually increases the risk of squamous cell carcinoma and nonmelanoma skin cancer. Therefore, selenium supplementation should be avoided in individuals at risk or with a history of nonmelanoma skin cancer.

D 

Skin disorders 

Taking selenium by mouth has been studied for its effects on psoriasis and lesions induced by arsenic. Selenium has also been used to treat eczema, to increase the rate of burn wound healing, and may be effective for the treatment of dermatitis herpetiformis. Currently available results fail to support a role for selenium in treating these various skin disorders.

D 

 

*Key to grades: 

A: Strong scientific evidence for this use;
B: Good scientific evidence for this use;
C: Unclear scientific evidence for this use;
D: Fair scientific evidence against this use (it may not work);
F: Strong scientific evidence against this use (it likely does not work).

For full grading rationale, click here.

Uses based on tradition or theory 

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified health care professional

Abnormal pap smears, acne, alcoholism, altitude sickness, Alzheimer's disease, arsenic poisoning, atherosclerosis (hardening of the arteries), benign prostatic hypertrophy (BPH), bone density, burns, cardiac arrhythmia (irregular heartbeat), celiac disease, cognitive disorders, cosmetic uses, Crohn's disease, depression, diabetic retinopathy, diarrhea, detoxification from alcohol or toxins, Down's Syndrome, ear infections, eczema, endocrine disorders, epilepsy, fetal development, Graves' disease, growth disorders (growing pains), hay fever, heart attack treatment/prevention/rehabilitation, hyperglycemia (high blood sugar), hyperlipidemia (high blood lipids), infant eye/brain development, inflammation, inflammatory bowel disease, lung disease, lupus erythematosus, lymphedema, menopausal symptoms, metabolic enhancement, miscarriage prevention, mood disorders, multiple organ failure, multiple sclerosis (MS), muscle weakness, neonatal disorders, non-Hodgkin's lymphoma, pain, parasites and worms, partial androgen deficiency, phenylketonuria, pneumonia, poison prophylaxis, radioprotection, Raynaud's phenomenon, sinusitis, skin aging, sleep apnea, stroke, sudden infant death syndrome (SIDS), systemic sclerosis, tuberculosis, vaccine adjunct, vasculitis, weight loss, wound healing.


Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy. Consult a healthcare professional immediately if you experience side effects.

Allergies

  • Selenium is a trace element and hypersensitivity is unlikely. Avoid with known allergy or hypersensitivity to products containing selenium.

Side Effects and Warnings

  • Chronic exposure and high intake of selenium have produced adverse effects, including death. Chronic exposure to organic and inorganic selenium may cause neurotoxicity, particularly motor neuron degeneration leading to an increased risk of amyotrophic lateral sclerosis (ALS). Nausea, vomiting, and liver dysfunction have been reported as a result of high selenium exposure. Excessive amounts of selenium may cause hair and nail loss, dermatitis, impaired endocrine function and neurotoxicity, selenosis (affects the liver, skin, nails, and hair), and dermatitis. Excessive selenium intake has also been associated with garlic odor on breath and a metallic taste.
  • Selenium may reduce serum levels of somatotropin (growth hormone) and insulin-like growth factor-1 (IGF-1), followed by growth retardation. Hypothyroidism, secondary to iodine deficiency, has been reported as a result of selenium intravenous administration. Selenium supplementation may reduce sperm motility.
  • Use cautiously at doses from 27-2,310 milligrams daily.
  • Use cautiously in patients on hemodialysis, as erythropoietin (EPO) and selenium taken together may increase selenium levels in these patients.
  • Use cautiously in patients with iodine deficiency, as hypothyroidism has been reported as a result of selenium supplementation.
  • Use cautiously in patients with high cholesterol, as high serum selenium concentrations have been associated with increased total and LDL cholesterol.
  • Use cautiously in patients with immune disorders or those using immunosuppressants, as selenium has been shown to stimulate the immune system.
  • Use cautiously in patients using corticosteroids, as these agents may lower selenium levels.
  • Use cautiously in patient using antacids, as these agents may reduce the absorption of selenium.
  • Use cautiously in patients using erythropoietin (EPO), as selenium may increase the effects of EPO.
  • Use cautiously in patients using HMG-CoA reductase inhibitors ("statins"), as selenium may reduce the effectiveness of these agents.
  • Use cautiously in patients using oral contraceptives, as these agents may reduce selenium levels.
  • Use cautiously in patients using astragalus, as this herb may cause selenium to accumulate in the body.
  • Use cautiously in patients taking iron supplements, as selenium levels may be affected by iron supplementation.
  • Avoid in patients at high risk of nonmelanoma skin cancer, as selenium supplementation has been shown to increase the risk of squamous cell carcinoma and nonmelanoma skin cancer.
  • Avoid in patients at risk for developing diabetes, as selenium supplementation may increase risk for type 2 diabetes.
  • Avoid in patients with known allergy/hypersensitivity to products containing selenium; however, selenium is a trace element, and hypersensitivity is unlikely.

Pregnancy and Breastfeeding

  • The U.S. recommended dietary allowance (RDA) of selenium for adults is 65 micrograms for pregnant females and 75 micrograms for breast-feeding females.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare professional before starting a new therapy.

Interactions with Drugs

  • Selenium may interact with anticoagulants and antiplatelets. However, available research results are conflicting.
  • Selenium may affect blood sugar levels. Caution is advised when using drugs that may also affect blood sugar. Patients taking drugs for diabetes by mouth or injection should be monitored closely by a qualified healthcare professional. Dosing adjustments may be necessary.
  • Selenium may also interact with anticancer agents, anti-inflammatory agents, barbiturates, cholesterol-lowering drugs, cisplatin, clozapine, corticosteroids, erythropoietin (EPO), estrogens, gastric acid-reducing agents, antiulcer agents, growth hormones, agents that affect the immune system, iron salts, thyroid hormones, or valproic acid.

Interactions with Herbs and Dietary Supplements

  • Selenium may interact with anticoagulants and antiplatelets. However, available research results are conflicting.
  • Selenium may affect blood sugar levels. Caution is advised when using herbs and supplements that may also affect blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.
  • Selenium may also interact with anti-cancer herbs and supplements, anti-inflammatory herbs and supplements, cholesterol-lowering herbs and supplements, antioxidants, astragalus, calcium, chromium, coenzyme Q10, diets high in refined foods, fish, fortified eggs (enriched with vitamin E, lutein, Se, and DHA), garlic, gastric acid reducing herbs and supplements, antiulcer herbs and supplements, herbs and supplements that affect the immune system, ketogenic diet, iodine, iron, omega-3 fatty acids, phytoestrogens, vitamin C, zinc, and a vegetarian diet.

Authors

Selected References

Natural Standard developed the above evidence-based information based on a systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

  1. Arnaud J, Arnault N, Roussel AM, et al. Relationships between selenium, lipids, iron status and hormonal therapy in women of the SU.VI.M.AX cohort. J Trace Elem Med Biol 2007;21 Suppl 1:66-9.
  2. Bardia A, Tleyjeh IM, Cerhan JR, et al. Efficacy of antioxidant supplementation in reducing primary cancer incidence and mortality: systematic review and meta-analysis. Mayo Clin Proc 2008;83(1):23-34.
  3. Bjelakovic G, Nikolova D, Gluud L., et al. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev 2008;(2):CD007176.
  4. Duffield-Lillico AJ, Slate EH, Reid ME, et al. Selenium supplementation and secondary prevention of nonmelanoma skin cancer in a randomized trial. J Natl Cancer Inst 2003;95(19):1477-1481.
  5. Etminan M, FitzGerald JM, Gleave M, et al. Intake of selenium in the prevention of prostate cancer: a systematic review and meta-analysis. Cancer Causes Control 2005;(9):1125-31.
  6. Hurwitz BE, Klaus JR, Llabre MM, et al. Suppression of human immunodeficiency virus type 1 viral load with selenium supplementation: a randomized controlled trial. Arch Intern Med. 2007 Jan 22;167(2):148-54.
  7. Lippman SM, Klein EA, Goodman, P. J., et al. Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). 2009;301(1):39-51.
  8. Rayman M, Thompson A, Warren-Perry M, et al. Impact of selenium on mood and quality of life: a randomized, controlled trial. Biol Psychiatry 2006;59(2):147-54.
  9. Reid ME, Duffield-Lillico AJ, Slate E, et al. The nutritional prevention of cancer: 400 mcg per day selenium treatment. Nutr Cancer 2008;60(2):155-163.
  10. Reid ME, Duffield-Lillico AJ, Sunga A, et al. Selenium supplementation and colorectal adenomas: an analysis of the nutritional prevention of cancer trial. Int J Cancer 2006 Apr 1;118(7):1777-81.
  11. Shaheen SO, Newson RB, Rayman MP, et al. Randomised, double blind, placebo-controlled trial of selenium supplementation in adult asthma. Thorax 2007;62(6):483-90.
  12. Stawicki SP, Lyons M, Aloupis M, et al. Current evidence from phase III clinical trials of selenium supplementation in critically Ill patients: why should we bother? Mini Rev Med Chem 2007;7(7):693-9.
  13. Stranges S, Marshall JR, Natarajan R, et al. Effects of long-term selenium supplementation on the incidence of type 2 diabetes: a randomized trial. Ann Intern Med 2007;21;147(4):217-23.
  14. Stranges S, Marshall JR, Trevisan M, et al. Effects of selenium supplementation on cardiovascular disease incidence and mortality: secondary analyses in a randomized clinical trial. Am J Epidemiol 2006;163(8):694-9.
  15. You WC, Brown LM, Zhang L, et al. Randomized double-blind factorial trial of three treatments to reduce the prevalence of precancerous gastric lesions. J Natl Cancer Inst 2006;98(14):974-83.
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