Doctors classify selenium as a trace mineral because, although your body needs selenium to function, it needs only small amounts. Your body incorporates selenium into proteins, producing selenoproteins. Some selenoproteins function as antioxidants, protecting cells from damage caused by negatively charged particles produced during chemical reactions in the body, while others regulate thyroid function.
Thyroid Function
The thyroid, a gland located in your neck, produces two hormones that regulate the conversion of oxygen and calories into energy -- a process known as metabolism. The chemical reactions to produce thyroid hormones also produce hydrogen peroxide, which can damage the cells in the thyroid gland. Selenium in your diet promotes the formation of selenoproteins that protect the thyroid cells from damage. This makes selenium important for maintaining normal thyroid function.
Hyperthyroidism
Research published in the journal "BMC Endocrine Disorders" states that patients with hyperthyroidism, a condition in which the thyroid gland produces too much thyroid hormone, show low levels of selenium in the blood. Hyperthyroidism, which affects approximately 1 percent of the population in the United States, occurs when the cells in the thyroid become inflamed, which may occur when the thyroid cells become damaged, according to the National Endocrine and Metabolic Diseases Information Service.
Recommended Intake
To avoid sustaining damage to your thyroid, you should consume at least 55 mg of selenium per day -- the intake recommended by the Institute of Medicine. In addition to impairing thyroid functions, a selenium deficiency can also weaken the immune system and promote the development of heart disease, as described by the National Institutes of Health Office of Dietary Supplements.
Sources
To increase your intake of selenium, doctors suggest you consume foods that contain high levels of selenium. Brazil nuts contain the highest level of selenium, with a 1 ounce serving providing 544 mg of selenium. Although the amount of selenium in the food depends upon the amount of selenium available in the soil where the food grows, other good sources of selenium include grains like oats, rice and wheat. Tuna, enriched noodles, eggs and cottage cheese also contain selenium. Consult your doctor before deciding to take selenium supplements, because too much selenium can cause intestinal upset, fatigue, irritability and hair loss.
References
- "BMC Endocrine Disorders"; The Role of Selenium, Vitamin C, and Zinc in Benign Thyroid Diseases and of Selenium in Malignant Thyroid Diseases: Low Selenium Levels Are Found in Subacute and Silent Thyroiditis and in Papillary and Follicular Carcinoma; Moncayo, R. et al.; January 2008
- National Institutes of Health Office of Dietary Supplements: Selenium; November 2009
- National Endocrine and Metabolic Diseases Information Service: Hyperthyroidism; April 2008
- Institute of Medicine: Dietary Reference Intakes; 2004
