Selenium is an essential micronutrient that plays a role in heart health, immune system function, eye health, and the inflammatory response. Selenium also plays a role in healthy functioning of the thyroid. Selenium is thought to help protect the body from cell damage due to free radicals. Selenium can be found in nuts, cereals, meat, fish, and eggs. Brazil nuts are the best dietary source and kidney, tuna, crab, and lobster also contain significant amounts of selenium. Some more unusual food sources include button mushrooms, shiitake mushrooms, sunflower seeds and mustard seeds.

Exposure to chemicals or the presence of vitamin E deficiency may be associated with selenium deficiency. Selenium interacts with other nutrients such as iodine and vitamin E. Some controversial studies have linked selenium to respiratory health, blood glucose stability, immune system strength and the body’s ability to resist tumor growth.

How much selenium is obtained from food is largely dependent on the level of selenium in the soil where the food is grown. Soils in the United States tend to be fairly high in selenium, but soils in many countries including China, Russia, Australia, New Zealand and Europe may be depleted. Some exceptions in the United States include the Pacific Northwest, parts of the Great Lakes region, parts of New England and parts of the Atlantic coast. People residing in the areas may want to consider selenium supplementation either as a single supplement or in a multivitamin.