› Health benefits
Scientists have been testing the effects on selenium supplementation for many different diseases.
Cancer
People who consume a lower amount of selenium have been found to have a higher risk of developing colon, rectal, prostate, lung, bladder, skin, esophagus and stomach cancers. More research needs to be done, as it is not clear whether selenium supplements will reduce the risk of these cancers.
Cognitive decline
Selenium levels in blood decrease with age, and there are studies underway to see whether a low blood level of selenium will contribute to a decline in brain function. Some of these studies have shown that people with lower levels of selenium in the blood are more likely to have poor mental function, but there have also been studies that have shown there is no link between selenium levels and memory. More research is needed.
Thyroid disease
The thyroid gland contains high amounts of selenium. Some studies have shown that those with low levels of selenium in the blood, especially women, may develop problems with the thyroid. More research is needed to confirm a link between the two.
› How much do I need?
The amount of selenium needed daily depends on age. Most people get enough selenium through their diet. If you are undergoing kidney dialysis, have HIV, or eat only local foods grown in soil that is low in selenium, then you may have trouble getting the recommended amount in your diet. People 14 and over need about 55 micrograms daily. Pregnant women need 60 micrograms daily; breastfeeding women, 70 micrograms.
Selenium deficiency is rare but can occur. It can cause Keshan disease, a type of heart disease, and male infertility. It may also cause a type of arthritis known as Kashin-Beck disease.
Selenium can be harmful in high dosages. Symptoms of too much selenium include garlic-smelling breath, nausea, diarrhea, irritability, skin rashes, brittle hair or nails, discolored teeth, loss of hair or nails, nervous system problems, and a metallic taste in the mouth. Severe issues related to ingestion of too much selenium can include difficulty breathing, tremors, kidney failure, heart attack and heart failure. The upper limit for selenium is about 400 micrograms for people ages 14 and older.
Some medications may interact with selenium supplements, and you should consult a doctor.
› In food
Selenium can be found in many foods, and the amount of selenium in plant foods is dependent on the amount of selenium in the soil where the food was grown. Just like in plants, the amount of selenium found in animal products is dependent on the amount of selenium in the foods consumed by the animal.
Foods that contain selenium include seafood, meat, poultry, eggs, dairy products, breads, cereals and other grain products.
› Dietary supplements
Selenium is available in multivitamin supplements and other supplements, and can be present in several forms, such as selenomethionine and sodium selenite.
Source: National Institutes of Health, Office of Dietary Supplements
Please consult your health care provider before making changes to your vitamin/supplement regimen.