What Are The Dangers Of Selenium?

The trace mineral selenium works in concert with vitamin E to destroy free radicals, substances that can trigger several types of diseases. Higher rates of cancer in certain areas with low levels of selenium in the soil have led to a theory that a deficiency of this nutrient increases cancer risk. Studies on whether supplementing with selenium decreases cancer risk have produced mixed results. Selenium's strong antioxidant properties suggest potential benefit for a range of conditions, but not enough evidence exists to draw any firm conclusions. When taken in appropriate doses, selenium supplements appear safe for most people, but some safety concerns exist regarding large doses or using them in certain circumstances. Talk to your doctor about whether it is appropriate to supplement with selenium.

Dose Considerations

The Beth Israel Deaconess Medical Center notes a tolerable upper intake limit of 400 mcg for anyone age 14 and older. Taking more than this could increase your risk of adverse effects associated with selenium. This maximum intake applies to selenium derived from supplements and your diet, which provides about 100 mcg daily. Studies of selenium for various conditions used doses between 100 mcg and 200 mcg a day; talk to your doctor about the right amount to take.

Increased Risk of Diabetes

The University of Maryland Medical Center notes follow-up of participants who took part in a study testing the effects of selenium on skin cancer recurrence found that individuals taking this supplement were more likely to develop diabetes compared to the placebo group. They took 200 mcg daily for a period of seven years. The findings were published in the August 2007 issue of the ''Annals of Internal Medicine.'' This one study cannot firmly establish causation, but if you have an increased risk of developing diabetes, keep this in mind.

Decreased Thyroid Function

Selenium plays a role in regulating thyroid function, but in certain cases, selenium supplements might negatively affect it. The University of Michigan Health System notes reports of selenium worsening low thyroid function in individuals with iodine deficiency.

Toxicity

The Beth Israel Deaconess Medical Center reports doses of 900 mcg or more can cause selenium toxicity. Symptoms include depression, nervousness, emotional instability, vomiting , vomiting, nausea, the loss of your hair and fingernails, muscle weakness, nerve damage, rash and liver damage.

Interactions

The Memorial Sloan-Kettering Cancer Center reports selenium might inhibit vitamin C absorption. The University of Maryland Medical Center notes several possible medication interactions. Selenium supplements might increase the risk of bleeding when used along with anti-coagulant medications; decrease the effectiveness of cholesterol medications and chemotherapy drugs; and prolong the sedative effects of barbiturates.