Selenium is a mineral that is important for good health. However, it’s only needed in small amounts. Most adults need 55 micrograms of selenium a day; pregnant and breastfeeding women need slightly more. Taking high doses of selenium supplements may increase the risk of some diseases. Selenium supplements can also have side effects and may interfere with medicines you may take.
Some research shows people with low levels of selenium may have a higher risk of developing non-melanoma skin cancer. Deaths from some cancers, including lung, colon and prostate cancers, have also been associated with low levels of selenium. But taking selenium supplements to lower your risk of cancer is controversial. Some research suggests taking selenium might increase the risk of a type of skin cancer called squamous cell carcinoma. Additionally, taking 200 micrograms of selenium doesn’t seem to reduce the risk of developing another non-melanoma skin cancer called basal cell carcinoma.
Diabetes and Other Conditions
Taking 200 micrograms of selenium a day for a long time could increase your risk of diabetes, reports the University of Maryland Medical Center. When researchers examined the possible effect of selenium on skin cancer, they found something surprising: People who took 200 micrograms per day for more than seven years had a significantly higher risk of developing type 2 diabetes. Additionally, high selenium intake can worsen hypothyroidism, or underactive thyroid, especially in people with iodine deficiency, according to MedlinePlus.
Side Effects and Drug Interactions
Over time, high doses of selenium can be toxic, according to UMMC. Side effects may include fingernail loss, skin rash, fatigue, irritability and weight loss. Selenium supplements can also interfere with a number of medicines, including medicines that slow blood clotting, such as aspirin and Plavix, some cholesterol-lowering medicines, certain sedatives and Warfarin, also known as Coumadin. Consult your doctor before taking selenium supplements.
There are no precautions associated with foods containing selenium. Brazil nuts are the best food source -- 1 ounce of Brazil nuts supplies more than seven times your recommended daily allowance for selenium, according to the ODS. Light tuna canned in water is also an excellent source of selenium. Three ounces supplies 97 percent of your daily requirement for the mineral. Other good sources include cod, turkey, chicken breast, beef chuck roast, bagels and sunflower seeds. Eating foods containing selenium is safe, but be cautious about taking selenium supplements.
Jan Sheehan is an award-winning medical and nutrition writer, having entered journalism in 1992. She is a former contributing editor for "Parents" magazine. She has also written nutrition articles for "Self," "Fitness," "Ladies' Home Journal," "Health" and other magazines. Sheehan has a Bachelor of Arts in journalism from Purdue University.