Selenium is a trace mineral that works as an antioxidant in the body. Selenium is incorporated into glutathione peroxidase, an antioxidant enzyme that plays a critical role in reducing free-radicals and oxidation in the body. Free-radicals are unstable oxygen molecules that are a byproduct of metabolism. Diet and lifestyle also impact the amount of free-radicals generated by the body.
Selenium and vitamin E are synergistic antioxidants which means they work better together than separately. Selenium can support the activity of vitamin E in limiting the oxidation of fats. Selenium also works with vitamin C, glutathione and vitamin B3 (niacin) to prevent oxygen molecules from becoming too reactive.
Low levels of selenium are linked to a higher risk for cardiovascular disease, stroke, cataracts and aging, all of which are associated with free-radical damage. In heart disease, oxidative stress damages blood vessels. Selenium may help by preventing the oxidation of LDL or “bad” cholesterol.
A great deal of evidence indicates a strong inverse relationship between selenium intake and cancer incidence. For example, the incidence of non-melanoma skin cancer is significantly higher in areas of the country where the selenium content of the soil is low. Selenium can affect cancer risk by protecting the body from free-radicals and preventing tumor growth. Observational studies have shown that individuals with higher selenium levels have a lower rate of death from cancer including lung, colorectal and prostate. Selenium’s anti-cancer effects are more significant in men than in women.
Selenium and glutathione peroxidase are low in patients with rheumatoid arthritis, eczema, psoriasis and other inflammatory conditions. In rheumatoid arthritis, oxidative stress damages the area around the joints. Selenium is important in reducing the production of inflammatory compounds (prostaglandins).
Selenium is incorporated into proteins that help regulate thyroid function and play a role in the immune system. For example, a selenium deficiency may contribute to hypothyroidism and a weakened immune system. Selenium supplementation stimulates white blood cell and thymus function.
Acts as an antioxidant protecting cells from free-radical damage
Inhibits the oxidation of fats and protects vitamin E
Supports thyroid and immune system function
The level of selenium in a food is directly related to the amount in the soil. Animals that eat grains or plants grown in selenium rich soil have a higher content of this mineral in their meat. Plants grown in selenium depleted soil contain lower amounts of this mineral.
One of the richest sources of selenium is Brazil nuts. Other good sources include finfish and shellfish, meats, eggs and some vegetables including mushrooms, asparagus and spinach.
Recommended Dietary Allowance
The Recommended Dietary Allowance (RDA) for selenium in adults is 55 mcg. The Upper Tolerable Limit for selenium is 400 mcg per day.
If you look on a nutritional supplement facts panel, you’ll notice the Amount Per Serving for selenium and the % Daily Values is at located at the top of the panel. The Amount Per Serving is based on the Reference Daily Intake (RDI) for this nutrient which is considered to be sufficient to meet the requirements of nearly all (97–98%) healthy individuals in each life-stage and sex group. The Reference Daily Intake for selenium is 70 mcg which represents 100% of the Daily Values.
While selenium deficiency is rare in the U.S., individuals with severe gastrointestinal problems like Crohn’s disease which impairs selenium absorption may have depleted levels of this mineral. Glucocorticoids, which are cortisol-based anti-inflammatory drugs, can reduce the body’s supply of selenium.
Energy Support and Bone Support are both formulated with 60 mcg of selenium. Multi-Vitamin & Mineral, which combines both products, provides 120 mcg of selenium. Anti-Aging Formula is formulated with 80 mcg of this mineral. Due to its beneficial effects on inflammatory conditions, both Healthy Skin Formula and Clear Skin Formula contain 48 mcg of selenium.
Last updated July 1, 2018
David H. Rahm, M.D. is the founder and medical director of The Wellness Center, a medical clinic located in Long Beach, CA. Dr. Rahm is also president and medical director of VitaMedica. Dr. Rahm is one of a select group of conventional medical doctors who have education and expertise in functional medicine and nutritional science. Over the past 20 years, Dr. Rahm has published articles in the plastic surgery literature and educated physicians about the importance of good peri-operative nutrition.