Selenium is an essential trace mineral, required for proper functioning of the immune system and thyroid gland.

The selenium content of foods depends upon the amount of selenium in the soil in which it was produced. In the United States, the high plains of northern Nebraska and the Dakotas have selenium-rich soil. China and Russia are known to have very low amounts of selenium in their soil and deficiencies are more common in those regions.

Selenium deficiency can cause serious health conditions, including an enlarged heart, a form of hypothyroidism that can lead to mental retardation, and an impaired immune system. A deficiency can also worsen symptoms of arthritis.

Selenium toxicity from food is very rare, because most foods have low levels of selenium. Brazil nuts are an exception, containing nearly 8 times the recommended daily allowance in just 6 nuts. Eating just a few Brazil nuts on a daily basis, or eating large quantities at one time, can cause toxicity symptoms. These symptoms include garlic breath odor, hair loss, white blotchy nails, irritability, fatigue, nausea, vomiting, and nerve damage.

US Recommended Daily Allowance: 70 mcg

Health Benefits of Selenium

Fertility A deficiency can cause low sperm count and sterility in men, and infertility in women.
Heart Lowers incidence of cardiovascular diseases by inhibiting LDL cholesterol oxidation.
Immune System - General A deficiency can impair the immune system.
Pancreas May help relieve pancreatic insufficiency.
Prostate Prevents cancer, especially prostate cancer.
Thyroid Helps combat autoimmune thyroid disease, such as Hashimoto's disease.

Food Sources of Selenium

Brazil Nuts 542 mcg 774% Because Brazil nuts are so high in selenium, eating too many at one time, or eating just a few nuts daily, for a prolonged period of time, can lead to selenium poisoning.
Sunflower Seeds 14.8 mcg 21%
Buckwheat 7 mcg 10%