Selenium is a trace mineral that is essential for good health but required only in small amounts. It is incorporated into many proteins (selenoproteins) and enzymes which serve important functions in the body. It is required to make superoxide dismutase and glutathione, both of which are important antioxidant enzymes, while selenoproteins also help regulate thyroid function and play a role in the immune system.
The recommended daily amount is 55 mircog/day. Serum levels are optimal between 1.0–1.9 micromols/L.
Health benefits of selenium
There is no doubt that maintaining adequate selenium levels will have long term benefits for health and immunity. The Linxian area of China has particularly low levels of selenium and is renowned for its high cancer incidence. Fortunately, an interventional trial involving 29,584 adults, showed that mineral and vitamin supplements which included selenium reduced the risk of cancer over a five-year period.
A French RCT which tested a supplement of low dose ascorbic acid (120mg), vitamin E (30 mg), beta-carotene (6 mg), selenium (100 μg), and zinc (20 mg), found a reduction in cancer after seven and a half years in men but not women. On the other hand, the Selenium and Vitamin E Cancer Prevention Trial (SELECT) randomised 43,887 men to receive either; selenium supplementation alone, vitamin E supplementation alone, a supplementation containing both, or a placebo, and revealed a significantly increased risk of prostate cancer among those who had taken either vitamin E or selenium supplement. If you are concerned about having too little or too much selenium in your diet +/- body, consider a serum micronutrient test.
What foods provide dietary selenium?
Plant foods and nuts are the major dietary sources of selenium. The content of selenium depends on the selenium content of the soil where plants are grown or animals raised. Soils in the high plains of northern USA have high levels of selenium, whereas those in Asia, central Europe and China are very low in selenium. Selenium can also be found in some meats and seafood. Animals that eat grains or plants grown in selenium-rich soil have higher levels of selenium in their muscle.
Examples of food sources of selenium – Micrograms – DV %
- Brazil nuts, dried, unblanched, 1 ounce – 544 – 780
- Tuna, light, canned in oil, drained, 3 ounces – 63 – 95
- Beef, cooked, 3½ ounces 35 – 50
- Spaghetti w/ meat sauce, frozen entrée, 1 serving 34 – 50
- Cod, cooked, 3 ounces 32 – 45
- Turkey, light meat, roasted, 3½ ounces 32 – 45
- Beef chuck roast, lean only, roasted, 3 ounces 23 – 35
- Chicken Breast, meat only, roasted, 3½ ounces 20 – 30
- Noodles, enriched, boiled, 1/2 cup 17 – 25
- Egg, whole, 1 medium 14 – 20
- Cottage cheese, low fat 2%, 1/2 cup 12 – 15
- Oatmeal, instant, fortified, cooked, 1 cup 12 – 15
- Rice, white, enriched, long-grain, cooked, 1/2 cup 12 15
- Walnuts, black, dried, 1 ounce 5 – 8
- Bread, enriched, white, commercially prepared, 1 slice 4 – 6
- Cheddar cheese, 1 ounce 4 – 6