Selenium is a trace mineral that is essential to good health but required only in small amounts. It is incorporated into many proteins (selenoproteins) and enzymes which have important functions for the body. It is required to make, superoxide dismutase and glutathione which are important antioxidant enzymes. Reducing free radicals are natural by-products of oxygen metabolism that contribute to the development of chronic diseases such as cancer and heart disease. Other selenoproteins help regulate thyroid function and play a role in the immune system.
The recommended daily amount is 55 mircog/day. Serum levels are optimum 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 a combinations of mineral and vitamin supplements including selenium reduced the risk of cancer after 5 years.
Selenium supplements 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 7.5 years, in men but not women. Further analysis of dietary patterns of men in the trial revealed that many were had deficiencies in these vitamins, which would explain the benefits. On the other hand, the Selenium and Vitamin E Cancer Prevention Trial (SELECT) randomised 43,887 men to selenium supplementation alone; vitamin E supplementation alone; a supplementation containing both, or placebo showed a significantly increased risk of prostate cancer with vitamin E and selenium supplementation after at least 7 years of follow-up. 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 are 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 also can be found in some meats and seafood. Animals that eat grains or plants that were grown in selenium-rich soil have higher levels of selenium in their muscle.
Examples of selected 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