Selenium (Se)

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.

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.

evidence table

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 provider.
 
Antioxidant (Grade: B)
Selenium is a component of the enzyme glutathione peroxidase, which has antioxidant properties in humans. Further research is needed.
Keshan disease (Grade: B)
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.
Prostate cancer prevention (Grade: B)
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.
Amyotrophic lateral sclerosis (ALS) (Grade: C)
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.
Asthma (Grade: C)
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.
Blood disorders (Grade: C)
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.
Cancer prevention (Grade: C)
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.
Cancer treatment (Grade: C)
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.
Cardiovascular disease (prevention) (Grade: C)
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.
Chemotherapy side effects (Grade: C)
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.
Colitis (inflammation of the large intestine) (Grade: C)
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.
Critical illness (Grade: C)
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.
Cystic fibrosis (Grade: C)
Preliminary research on the effect of selenium supplementation in cystic fibrosis patients yields indeterminate results. Further research is needed in this area.
Dandruff (Grade: C)
Selenium sulfide may help improve dandruff. Selenium is included in some commercially available shampoos. More research is needed.
Dialysis (Grade: C)
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.
Eye disorders (Grade: C)
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.
Fatigue (associated with primary biliary cirrhosis) (Grade: C)
Antioxidant supplementation, including selenium, has been studied for treating fatigue associated with biliary cirrhosis. Evidence of benefit is inconclusive. More research is needed.
Heavy metal/lead toxicity (Grade: C)
Zinc and selenium have been shown to exert protective effects against mercury toxicity. More research is needed before a conclusion can be drawn.
High blood pressure (Grade: C)
Some studies have reported a possible relationship between low serum selenium levels and increased blood pressure. Additional study is needed in this area.
HIV/AIDS (Grade: C)
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.
Immune stimulation (Grade: C)
Selenium may help prevent infection by stimulating immune function. Further research is needed before a conclusion can be made.
Infection prevention (Grade: C)
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.
Infertility (Grade: C)
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.
Intracranial pressure symptoms (Grade: C)
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.
Liver disease (Grade: C)
Selenium supplementation has been studied in various liver disorders, including hepatitis, cirrhosis, and liver cancer, with mixed results. More study is needed.
Longevity/anti-aging (Grade: C)
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.
Low birth weight (Grade: C)
Selenium supplementation has been studied in low birth weight infants. Additional study is needed before a clear conclusion can be drawn.
Malabsorption (Grade: C)
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.
Nutritional support (Grade: C)
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.
Pancreatitis (Grade: C)
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.
Physical endurance (Grade: C)
Available evidence suggests that selenium supplementation lacks effect on physical performance or endurance training. Additional studies are needed.
Post-operative recovery (Grade: C)
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.
Pregnancy-related complications (Grade: C)
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.
Quality of life (Grade: C)
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.
Radiation side effects (Grade: C)
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.
Respiratory tract infections (Grade: C)
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.
Rheumatoid arthritis (Grade: C)
Selenium supplementation has been studied in rheumatoid arthritis patients with mixed results. Additional research is necessary before a clear conclusion can be made.
Seizures (Grade: C)
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.
Sepsis (severe bacterial infection of the blood) (Grade: C)
Study results of selenium supplementation in septic patients are mixed. Research using selenium alone is needed.
Sunburn prevention (Grade: C)
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.
Thyroid conditions (Grade: C)
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.
Yeast infections (Grade: C)
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.
Diabetes (prevention) (Grade: D)
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.
Kashin-beck osteoarthropathy (Grade: D)
Kashin-Beck disease is an osteoarthropathy common in selenium- and iodine-deficient areas. Preliminary evidence suggests that selenium supplementation lacks effectiveness.
Muscle and joint disorders (Grade: D)
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.
Osteoarthritis (Grade: D)
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.
Skin cancer (nonmelanoma) prevention (Grade: D)
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.
Skin disorders (Grade: D)
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.