Selenium is a trace mineral that our bodies use to produce glutathione peroxidase. Glutathione peroxidase is part of the body's antioxidant defense system; it works with vitamin E to protect cell membranes from damage caused by dangerous, naturally occurring substances known as free radicals.

China has very low rates of colon cancer, presumably because of the nation's low-fat diet. However, in some parts of China where the soil is depleted of selenium, the incidence of various types of cancer is much higher than in the rest of the country. This fact has given rise to a theory that selenium deficiency is a common cause of cancer, and that selenium supplements can reduce this risk.

As we will see, there is some preliminary evidence that selenium supplements might provide some protection against some types of cancer among people living in the US, but this evidence is far from definitive.

Requirements

The official US and Canadian recommendations for daily intake of selenium are as follows:

  • Infants
    • 0-6 months: 15 mcg
    • 7-12 months: 20 mcg
  • Children
    • 1-3 years: 20 mcg
    • 4-8 years: 30 mcg
    • 9-13 years: 40 mcg
  • Males and Females
    • 14 years and older: 55 mcg
  • Pregnant Women: 60 mcg
  • Nursing Women: 70 mcg
Sources

Selenium content of food varies depending on the selenium content of the soil in which it was grown. Studies suggest that many people in certain developed countries, including New Zealand, Belgium, and Scandinavia, do not get enough selenium in their diets.3-6However, most people in the US and Canada are believed to consume sufficient quantities of selenium.46

Foods containing significant and reliable amounts of selenium include animal products like meat, seafood, and dairy foods, as well as whole grains and other foods grown in selenium-rich soils, especially Brazil nuts. The table below from the Office of Dietary Supplements provides a more complete list of the selenium content in certain foods and the percent daily value.69

Food Serving size Selenium content
(micrograms [mcg])
% Daily Value
Brazil nuts, dried 1 ounce 544 777
Tuna, light, canned in water, drained 3 ounces 68 97
Cod, cooked 3 ounces 32 46
Turkey, roasted 3 ounces 27 39
Bagel 1 27 39
Chicken breast, roasted 3 ounces 24 34
Beef chuck roast, lean, roasted 3 ounces 23 33
Sunflower seed, dry roasted 1 ounce 23 33
Enriched egg noodles, boiled ½ cup 19 27
Enriched macaroni, boiled ½ cup 19 27
Ground beef, broiled 3 ounces 18 26
Hard-boiled egg 1 large 15 21
Fortified instant oatmeal 1 cup 12 17
Low-fat cottage cheese ½ cup 11 16
Whole-wheat bread 1 slice 11 16
Long-grain brown rice ½ cup 10 14
Enriched long-grain white rice ½ cup 6 9
White bread 1 slice 6 9
Black walnuts 1 ounce 5 7
Cheddar cheese 1 ounce 4 6
Selenium Absorption

Certain digestive conditions, such as Crohn’s disease, short-bowel syndrome, and ulcerative colitismay impair selenium absorption.47 In addition, medications that reduce stomach acid such as proton pump inhibitors or H2blockersmay reduce absorption of selenium.12