The Who, What, Where, When and Sometimes, Why.

Selenium

Selenium

What is it?

Selenium is a mineral. It is taken into the body in water and foods. People use it for medicine.

Most of the selenium in the body comes from the diet. The amount of selenium in food depends on where it is grown or raised. Crab, liver, fish, poultry, and wheat are generally good selenium sources. The amount of selenium in soils varies a lot around the world, which means that the foods grown in these soils also have differing selenium levels. In the U.S., the Eastern Coastal Plain and the Pacific Northwest have the lowest selenium levels. People in these regions naturally take in about 60 to 90 mcg of selenium per day from their diet. Although this amount of selenium is adequate, it is below the average daily intake in the U.S., which is 125 mcg.

Selenium is used for diseases of the heart and blood vessels, including stroke and “hardening of the arteries” (atherosclerosis). It is also used for preventing various cancers including cancer of the prostate, stomach, lung, and skin.

Some people use selenium for under-active thyroid, osteoarthritis, rheumatoid arthritis (RA), an eye disease called macular degeneration, hay fever, infertility, cataracts, gray hair, abnormal pap smears, chronic fatigue syndrome (CFS), mood disorders, arsenic poisoning, and preventing miscarriage.

Selenium is also used for preventing serious complications and death from critical illnesses such as head injury and burns. It is also used for preventing bird flu, treating HIV/AIDS, and reducing side effects from cancer chemotherapy.

Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

The Effectiveness ratings for Selenium are as follows:

Likely Effective for…

  • Selenium deficiency. Taking selenium by mouth is effective for preventing selenium deficiency.

Possibly Effective for…

  • Autoimmune thyroiditis (Hashimoto’s thyroiditis). Research shows that taking up to 200 mcg of selenium daily along with thyroid hormone might decrease antibodies in the body that contribute to this condition. Selenium might also help improve mood , general feelings of well-being , and quality of life in people with this condition. Taking selenium doses under 200 mcg daily might not be as effective, and it might be more beneficial in people with more severe cases.
  • Abnormal cholesterol levels. Some research shows that taking 100-200 mcg of selenium daily for 6 months can modestly reduce cholesterol levels. Many people in this study had low levels of selenium in their body before the start of the study. It is not clear if taking extra selenium would have any benefit on cholesterol levels in people with normal selenium levels in the body.
  • Blood infection (sepsis). Research shows that giving selenium along with other nutrients intravenously reduces the risk of death by 11% to 27% in people with a life-threatening blood infection called sepsis. But it does not seem to reduce the recovery time in the hospital or the risk of pneumonia or kidney failure.
  • Bone and joint disease (Kashin-Beck disease). Some research shows that adding salt enriched with selenium to food can prevent Kashin-Beck disease in children. But selenium does not seem to improve joint pain or movement in children with Kashin-Beck disease.
  • A pregnancy complication marked by high blood pressure and protein in the urine (pre-eclampsia). Pregnant women with low levels of selenium in the blood might have a higher chance of developing pre-eclampsia. Pre-eclampsia is a serious complication of pregnancy. Pregnant women taking selenium 60-100 mcg daily for up to 6 months during pregnancy might have a lower chance of having pre-eclampsia.

Possibly Ineffective for…

  • Asthma. There is no link between selenium blood levels and asthma. Taking 100 mcg of selenium daily for up to 24 weeks does not seem to improve quality of life, lung function, asthma symptoms, or inhaler use in people with asthma.
  • Eczema (atopic dermatitis). Taking yeast that is enriched with 600 mcg of selenium daily for 12 weeks, alone or with vitamin E, does not improve the severity of eczema.
  • Bladder cancer. Taking selenium does not appear to prevent bladder cancer.
  • Heart disease. Taking selenium does not appear to reduce the risk of heart disease. In people who already have heart disease, taking 100 mcg of selenium in combination with beta-carotene, vitamin C, and vitamin E does not seem to prevent the condition from becoming worse. Also, taking 200 mcg of selenium daily for almost 8 years does not reduce the chance of developing heart disease.
  • Critical illness (burns, head injury, trauma). Selenium given intravenously (by IV) or by mouth does not seem to reduce the risk of death or infection in critically ill people.
  • Diabetes. Some research shows that people with low selenium levels have a higher chance of developing type 2 diabetes. But other research shows that people with high levels of selenium and older people taking selenium supplements also have an increased risk of type 2 diabetes. Additionally, people who take 200 mcg of selenium daily for about 7.7 years have an increased chance of developing type 2 diabetes. People with diabetes who take selenium for 2-3 months do not have improvements in blood sugar.
  • Hepatitis C. Taking 200 mcg of selenium along with vitamin C and vitamin E for 6 months does not improve liver function or virus levels in people with hepatitis C.
  • Infertility. Taking 100-200 mcg of selenium daily, alone or with vitamin A, vitamin C, and vitamin E, for 3-4 months does not improve sperm function in infertile men.
  • Low birth weight. Selenium does not appear to reduce the chance of death in low birth weight infants. But it might reduce the chance of an infection called sepsis.
  • Lung cancer. Early research showed that taking 200 mcg if selenium daily reduced the risk of lunch cancer by about 46% in people without selenium deficiency. However, a re-evaluation of this study shows that selenium did not reduce lung cancer risk in most people, but it did seem to benefit people with low selenium levels. Other research shows that taking selenium alone or with other nutrients does not reduce lung cancer risk.
  • Prostate cancer. There has been a lot of interest in studying whether taking selenium lowers the chance of getting prostate cancer. The interest was triggered by the finding that prostate cancer seems to be less common in men with higher selenium levels in their bodies. To date, there have been several large, long-term scientific studies. Most of this evidence suggests that selenium does not reduce the chance of getting prostate cancer.
  • Red and irritated skin (psoriasis). Taking yeast enriched with 600 mcg of selenium daily does not seem to reduce the severity of psoriasis.
  • Skin cancer. Taking 200 mcg of selenium does not seem to reduce the risk of getting a certain type of skin cancer called basal cell carcinoma. In fact, some scientific evidence suggests that taking extra selenium might actually increase the risk of getting another type of skin cancer called squamous cell carcinoma.

Insufficient Evidence to Rate Effectiveness for…

  • Arsenic poisoning. Early research shows that taking yeast enriched with selenium seems to decrease how much arsenic the body absorbs in Chinese people exposed to high levels of arsenic in the environment.
  • Cancer. Most research shows that taking selenium does not reduce the risk of cancer or cancer-related death. However, older studies suggest that it might reduce cancer risk by 24% and cancer-related death especially in men.
  • Cataracts. A clinical study shows that taking 200 mcg of selenium daily with or without vitamin E daily for around 5.6 years does not reduce the risk of age-related cataracts in men.
  • Abnormal cells on the surface of the cervix (cervical dysplasia). Early research shows that taking 200 mcg of selenium daily might reduce the amount of abnormal cells on the cervix in women with a specific type of cervical dysplasia called cervical intraepithelial neoplasia or CIN.
  • Colon and rectal cancer. Early research suggests that blood levels of selenium are not linked with the risk of colon and rectal cancer. Also, most research shows that taking selenium does not reduce the risk of colon and rectal cancer. But some research shows that selenium reduces the risk of colon and rectal cancer in some patients. Reasons for the conflicting findings are not clear. Different selenium formulas and type of colon cancer might affect findings. Also, selenium might work better in people with lower blood levels of selenium before treatment. Some early research shows that taking selenium with other antioxidants might protect against recurrence of polyps in the colon. Selenium alone seems to protect against recurrence of only certain type of advanced polyps.
  • Dementia. Early research shows that taking 200 mcg of selenium daily for 4 years does not prevent dementia.
  • Kidney disease in people with diabetes. Research shows that taking selenium reduces insulin resistance but does not improve blood sugar or kidney function in people with kidney disease and diabetes.
  • Esophageal cancer. Taking selenium supplements does not seem to lower the risk of esophageal cancer.
  • HIV/AIDS. There is contradictory evidence about the effect of selenium supplements on HIV. Some evidence shows that taking selenium daily for up to 2 years can slow how quickly HIV spreads and can increase immune function. However, other early research shows that selenium has no effect.
  • High thyroid hormone levels (hyperthyroidism). Research shows that giving selenium with drug therapy does not improve symptoms in people with Grave’s hyperthyroidism.
  • Low thyroid hormone levels (hypothyroidism). Some research shows that taking a selenium supplement might increase the conversion of thyroid hormones in older people. However, other research suggests that it has no benefit. Taking selenium can make hypothyroidism worse in people who are iodine deficient. Taking selenium daily during pregnancy seems to reduce the risk of developing thyroid dysfunction after pregnancy and permanent hypothyroidism.
  • Liver cancer. Early research in China suggests that taking selenium for 2-5 years can reduce the occurrence of liver cancer. It is unclear if taking selenium will reduce the risk of liver cancer in Western countries.
  • Mercury poisoning. Early research shows that taking yeast enriched with selenium seems to decrease how much mercury the body absorbs in Chinese people exposed to high levels of mercury in the environment.
  • Muscular dystrophy. Early research suggests that taking a water-soluble form of selenium daily for 6 months does not benefit people with muscular dystrophy.
  • Osteoarthritis. Low selenium levels seem to be linked with an increased risk of developing osteoarthritis. However, it is not known if selenium supplements can prevent osteoarthritis.
  • Ovarian cancer. Research suggests that there is no link between selenium consumption in the diet and the risk for ovarian cancer.
  • Overall risk of death. Analysis of many studies suggests that taking selenium does not seem to have an effect on overall death risk. However, some research suggests that taking 100 mcg of selenium along with zinc, vitamin C, vitamin E, and beta-carotene daily for 7.5 years might lower the risk of death from any cause in men, but not women. Other research suggests that selenium, taken alone or with other nutrients, does not reduce the risk of death.
  • Cancer of the pancreas. Increased selenium intake has been linked with a reduced risk of cancer of the pancreas.
  • Pancreatitis. Evidence is conflicting about the effect of selenium on pancreatitis. Some research suggests that selenium has no benefit. However, other research suggests that taking a water-soluble form of selenium daily might reduce the risk of death caused by severe pancreatitis.
  • Swelling in the arms and legs after surgery. Early evidence suggests that taking selenium supplements for 15 weeks might prevent bacterial skin infections in women with swelling in the arms and legs after breast cancer surgery.
  • Pregnancy complication associated with high blood pressure (pre-eclampsia). Research shows that women with low blood levels of selenium might be at a higher risk of developing pre-eclampsia, a serious complication of pregnancy associated with high blood pressure and severe leg swelling. Pregnant women taking selenium 60-100 mcg daily for up to 6 months during pregnancy might have a reduced risk of pre-eclampsia.
  • High blood pressure during pregnancy. Early research suggests that taking 100 mcg of selenium liquid daily for 6-8 weeks during pregnancy can reduce the occurrence of high blood pressure.
  • Diarrhea from radiation treatments. Early research suggests that taking 500 mcg of selenium on days of radiation therapy and 300 mcg on days without treatments reduces diarrhea by about 54%.
  • Rheumatoid arthritis (RA). Evidence on the effects of selenium on rheumatoid arthritis is mixed. Some research suggests that taking yeast enriched with 200 mcg of selenium does not improve RA. However, other research suggests that taking 200 mcg of selenium daily for 3 months reduces joint swelling, tenderness, and stiffness in people with RA.
  • Statin-induced myopathy. Early research suggests that taking 200 mcg of selenium daily with or without coenzyme Q10 for 3 months does not improve symptoms of statin-induced myopathy.
  • Abnormal pap smears.
  • Alcohol-related liver disease.
  • Atherosclerosis.
  • Bird flu and swine flu.
  • Burns.
  • Cataracts.
  • Chemotherapy side effects.
  • Chronic fatigue syndrome (CFS).
  • Destruction of the bile ducts in the liver (cirrhosis).
  • Enlarged prostate.
  • Gray hair.
  • Hay fever.
  • Hearing loss caused by the cancer drug cisplatin.
  • Heart failure.
  • Inflammatory bowel disease (ulcerative colitis).
  • Macular degeneration (eye disease).
  • Mood disorders.
  • Preventing miscarriage.
  • Stomach cancer.
  • Toxicity from cancer drugs.
  • Other conditions.

More evidence is needed to rate selenium for these uses.

Selenium is important for making many body processes work correctly. It seems to increase the action of antioxidants.

Selenium is LIKELY SAFE for most people when taken by mouth in doses less than 400 mcg daily, short-term.

Selenium is POSSIBLY UNSAFE when taken by mouth in high doses or for long-term. Taking doses above 400 mcg can increase the risk of developing selenium toxicity. Taking lower doses long-term can increase the risk of developing diabetes. High doses of selenium can cause significant side effects including nausea, vomiting, nail changes, loss of energy, and irritability. Poisoning from long-term use is similar to arsenic poisoning, with symptoms including hair loss, white horizontal streaking on fingernails, nail inflammation, fatigue, irritability, nausea, vomiting, garlic breath odor, and a metallic taste.

Selenium can also cause muscle tenderness, tremor, lightheadedness, facial flushing, blood clotting problems, liver and kidney problems, and other side effects.

Special Precautions & Warnings:

Children: Selenium is POSSIBLY SAFE when taken by mouth appropriately. Selenium seems to be safe when used in the short-term in doses below 45 mcg daily for infants up to age 6 months, 60 mcg daily for infants 7 to 12 months, 90 mcg daily for children 1 to 3 years, 150 mcg daily for children 4 to 8 years, 280 mcg daily for children 9 to 13 years, and 400 mcg daily for children age 14 years and older.

Pregnancy and breast-feeding: Selenium use is POSSIBLY SAFE during pregnancy and breast-feeding when used short-term in amounts that are not above 400 mcg daily. Selenium is POSSIBLY UNSAFE in pregnancy and breastfeeding when taking by mouth in doses above 400 mcg daily, as this might cause toxicity.

Autoimmune diseases: Selenium might stimulate the immune system. In theory, selenium might make autoimmune disease worse by stimulating the activity of the disease. People with autoimmune diseases such as multiple sclerosis, systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and other should avoid taking selenium supplements.

Hemodialysis: Blood levels of selenium can be low in people undergoing hemodialysis. Using a dialysis solution with selenium might increase selenium levels, but selenium supplementation might be needed for some people.

Fertility problems in men: Selenium might decrease the ability of sperm to move, which could reduce fertility. If you are trying to father a child, don’t take selenium supplements.

Skin cancer: Long-term use of selenium supplements might slightly increase the risk of skin cancer recurrence, but this is controversial. Until more is known about the possible increase in skin cancer risk, avoid long-term use of selenium supplements if you have ever had skin cancer.

Under-active thyroid (hypothyroidism): Taking selenium can worsen hypothyroidism especially in people with iodine deficiency. In this case, you should take iodine along with selenium. Check with your healthcare provider.

Surgery: Selenium might increase the risk of bleeding during and after surgery. Stop taking selenium at least 2 weeks before a scheduled surgery.

Birth control pills (Contraceptive drugs)

Interaction Rating = Minor Be watchful with this combination.
Talk with your health provider.

Some research shows that women who take birth control pills might have increased blood levels of selenium. However, other research shows no change in selenium levels in women who take birth control pills. There isn’t enough information to know if there is an important interaction between birth control pills and selenium.

Some birth control pills include ethinyl estradiol and levonorgestrel (Triphasil), ethinyl estradiol and norethindrone (Ortho-Novum 1/35, Ortho-Novum 7/7/7), and others.

Gold salts

Interaction Rating = Minor Be watchful with this combination.
Talk with your health provider.

Gold salts bind to selenium and decrease selenium in parts of the body. This might decrease the normal activity of selenium, possibly resulting in symptoms of selenium deficiency.

Gold salts include aurothioglucose (Solganal), gold sodium thiomalate (Aurolate), and auranofin (Ridaura).

Medications that decrease the immune system (Immunosuppressants)

Interaction Rating = Moderate Be cautious with this combination.
Talk with your health provider.

Selenium might stimulate the immune system. By stimulating the immune system, selenium might decrease the effectiveness of medications that decrease the immune system.

Some medications that decrease the immune system include azathioprine (Imuran), basiliximab (Simulect), cyclosporine (Neoral, Sandimmune), daclizumab (Zenapax), muromonab-CD3 (OKT3, Orthoclone OKT3), mycophenolate (CellCept), tacrolimus (FK506, Prograf), sirolimus (Rapamune), prednisone (Deltasone, Orasone), and other corticosteroids (glucocorticoids).

Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)

Interaction Rating = Moderate Be cautious with this combination.
Talk with your health provider.

Selenium might slow blood clotting. Taking selenium along with medications that also slow blood clotting might increase the chances of bruising and bleeding.

Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, ticlopidine (Ticlid), warfarin (Coumadin), and others.

Medications used for lowering cholesterol (Statins)

Interaction Rating = Moderate Be cautious with this combination.
Talk with your health provider.

Taking selenium, beta-carotene, vitamin C, and vitamin E together might decrease the effectiveness of some medications used for lowering cholesterol. It is not known if selenium alone decreases the effectiveness of medications used for lowering cholesterol.

Some medications used for lowering cholesterol include atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Mevacor), and pravastatin (Pravachol).

Niacin

Interaction Rating = Moderate Be cautious with this combination.
Talk with your health provider.

Taking selenium along with vitamin E, vitamin C, and beta-carotene might decrease some of the beneficial effects of niacin. Niacin can increase levels of good cholesterol. Taking selenium along with these other vitamins might decrease how well niacin works for increasing good cholesterol.

Sedative medications (Barbiturates)

Interaction Rating = Moderate Be cautious with this combination.
Talk with your health provider.

The body breaks down medications to get rid of them. Selenium might slow how fast the body breaks down sedative medications (barbiturates). Taking selenium with these medications might increase the effects and side effects of these medications.

Warfarin (Coumadin)

Interaction Rating = Moderate Be cautious with this combination.
Talk with your health provider.

Selenium might thin the blood. Selenium might also increase the effects of warfarin in the body. Taking selenium along with warfarin might increase the chances of bruising and bleeding.

Astragalus

Some species of astragalus accumulate large amounts of selenium, especially when grown in selenium-rich soils. Taking products made from these plants along with selenium supplements could cause selenium poisoning. However, most astragalus supplements contain Astragalus membranaceus, which is not a selenium accumulator.

Copper

Selenium might increase how quickly the body processes removes copper. In theory, taking selenium might reduce copper levels in the body.

Herbs and supplements that might slow blood clotting

Using selenium with other herbs that can slow blood clotting might increase the risk of bleeding in some people. These other herbs include angelica, clove, danshen, garlic, ginger, ginkgo, Panax ginseng, and others.

Omega-3 fatty acids

Taking selenium with omega-3 fatty acids might reduce how much selenium the body absorbs.

Vitamin C

Taking vitamin C might affect how much selenium the body absorbs from some supplements. However, it is unlikely that this potential interaction is a big concern.

Zinc

Zinc might make it more difficult for the body to absorb selenium from food.

There are no known interactions with foods.

The following doses have been studied in scientific research:

BY MOUTH:

  • Autoimmune thyroiditis (Hashimoto’s thyroiditis): 200 mcg daily.
  • High cholesterol: 100-200 mcg daily of a specific selenium product (SelenoPrecise, Pharma Nord, Denmark).

The daily recommended dietary allowances (RDAs) of selenium are:

  • Children 1-3 years, 20 mcg; children 4-8 years, 30 mcg; children 9-13 years, 40 mcg;
  • People over 13 years, 55 mcg;
  • Pregnant women, 60 mcg; and lactating women, 70 mcg. Due to the demands of the fetus on the mother, the dietary need for selenium increases during pregnancy.
  • The RDA for infants has not been determined. For infants up to 6 months old, 2.1 mcg/kg is adequate intake (AI). The AI for infants 7-12 months is 2.2 mcg/kg per day.

The tolerable upper limit is:

  • Adults, 400 mcg per day for adults and adolescents 14 years and older.
  • The tolerable upper intake level (UL) for infants up to age 6 months is 45 mcg per day;
  • Infants 7 to 12 months, 60 mcg per day;
  • Children 1 to 3 years, 90 mcg per day;
  • Children 4 to 8 years, 150 mcg per day;
  • Children 9 to 13 years, 280 mcg per day.

Atomic number 34, Dioxyde de Sélénium, Ebselen, L-Selenomethionine, L-Sélénométhionine, Levure Sélénisée, Numéro Atomique 34, Se, Selenio, Selenite, Sélénite de Sodium, Sélénium, Selenium Ascorbate, Selenium Dioxide, Selenized Yeast, Selenomethionine, Sélénométhionine, Sodium Selenite.


 

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