The Health Benefits of Selenium

Selenium is a trace mineral, which means that your body only needs a small amount of it. Selenium combines with proteins in the body to form antioxidants called selenoproteins, which help protect the cells in your body from free radical damage. Selenium is also essential for normal thyroid function, reproduction, and DNA synthesis.

Health Benefits

Selenium has been recommended as an antioxidant supplement for prevention of cancer and heart disease. However, a 2018 review of previous studies found that taking selenium had no impact on any type of cancer risk.

A 2015 review that focused on selenium and heart disease risk found an inverse correlation with selenium intake and heart disease. However, when they looked at previous studies that looked at selenium supplements, they didn't find clear evidence that selenium supplements actually prevented heart disease.

Possible Side Effects

Selenosis (having too much selenium in your body) results in gastrointestinal symptoms, hair loss, white blotchy nails, garlic breath odor, fatigue, irritability, and mild nerve damage. The National Academy of Sciences set a tolerable upper dietary intake level for selenium at 400 micrograms per day for adults.

Selenium toxicity usually occurs from industrial exposure to selenium and not by taking dietary supplements, but it is possible to ingest too much selenium if you regularly take large doses.

Speak with your doctor before taking large doses of any dietary supplement, including selenium, and follow the directions on the product label.

Dosage and Preparation

The National Academies of Sciences, Engineering, and Medicine, Health and Medicine Division sets the Dietary Reference Intakes (DRIs) for vitamins and minerals. The DRIs for selenium are based on age, plus women who are pregnant or breastfeeding need a little more. 

These DRIs reflect the amount of selenium needed by a person in good health. If you have any medical conditions, you might want to speak to your healthcare provider about your dietary needs, including selenium.

Dietary Reference Intakes for Selenium

• 1 to 3 years: 20 micrograms per day
• 4 to 8 years: 30 micrograms per day
• 9 to 13 years: 40 micrograms per day
• 14+ years: 55 micrograms per day
• Women who are pregnant: 60 micrograms per day
• Women who are breastfeeding: 70 micrograms per day

Selenium deficiency is rare in developed countries because it's easily obtained from foods. People with some kidney diseases that require hemodialysis and AIDs may be at a higher risk for deficiency.

What to Look For

Selenium is found in many plant-based foods, such as whole grains and nuts, as well as most animal-based foods. Seafood and organ meats are the richest sources, followed by meats, cereal, and dairy. Eggs, fish, and poultry contribute a significant amount to the average diet as well.

You can also purchase selenium supplements at your local vitamin shop or pharmacy. You'll see often the supplement in the forms of selenomethionine, selenium-enriched yeast, or sodium selenite. Selenium is also often included in multivitamins.

It is unclear, however, how well the body absorbs selenium in supplement form.

When purchasing any supplement, the National Institutes of Health recommends that consumers examine the Supplement Facts label before purchasing to make sure that they are getting the proper amount of the vitamin or mineral. The label will tell you how much of the micronutrient is contained in each serving and also if there are any added ingredients.

Lastly, NIH suggests that you look for a product that contains a seal of approval from a third party organization that provides quality testing. These organizations include U.S. Pharmacopeia, ConsumerLab.com, and NSF International. A seal of approval from one of these organizations does not guarantee the product's safety or effectiveness but it does provide assurance that the product was properly manufactured, contains the ingredients listed on the label, and does not contain harmful levels of contaminants.