Selenium is an essential nutrient that your body uses in minute quantities known as micrograms. Selenium plays an important role as an antioxidant and also contributes to thyroid function. Selenium deficiency is rare; however, toxicity can occur from ingesting foods grown in soil with particularly high levels of selenium, or through over-supplementation. Consult with a qualified health-care professional before supplementing with selenium.
Cancer
Selenium may protect against lung cancer, according to a study published in the 2011 issue of the "Chinese Journal of Lung Cancer." Researchers tested selenium levels in female residents of an area of China with a particularly high incidence of lung cancer and found that women with lung cancer had significantly lower levels of selenium than a lung cancer-free control group. The researchers concluded that selenium levels may be a risk factor for lung cancer.
Thyroid
Your thyroid gland functions optimally with the help of selenium and selenium status influences thyroid function. When selenium levels are low, particularly during serious illness, thyroid function suffers and thyroid hormone levels fall out of balance. In a study published in the September 2010 issue of the journal "PLoS One," scientists found that laboratory mice with hypothyroidism also had low selenium levels. Conversely, mice with hyperthyroidism had increased selenium levels. The researchers concluded that selenium and thyroid function share a feedback system that accounts for the hypothyroid condition that occurs in some seriously ill patients.
Immune Function
Immune function gets a boost from selenium. In a study published in the February 2011 issue of the "Journal of Immunology," researchers found that low selenium levels made laboratory mice more susceptible to West Nile virus and adequate selenium levels were more able to fend off the virus. The researchers concluded that dietary selenium significantly enhances immune response.
Toxicity
From its discovery in the early 1800's until the 1950's, when it was classified as an essential nutrient, selenium was regarded as poisonous, according to the University of California Berkeley Wellness Letter, December 2005. More recently, selenium has garnered considerable attention for its beneficial role in preventing or treating certain health conditions, notably some forms of cancer. The recommended daily allowance of selenium is a mere 55 micrograms. In the United States, the soil generally contains adequate levels and most people consume adequate amounts of selenium through diet. Selenium toxicity can occur from over-consumption over a long period of time. Characteristics include brittle hair and nails, fatigue, nerve-related symptoms and digestive disorders. The current upper limit for selenium intake set by the Institute of Medicine is 400 micrograms per day.
References
- "Chinese Journal of Lung Cancer"; [Serum and lung tissue selenium measurements in subjects with lung cancer from Xuanwei, China]. [Article in Chinese] Zhou L, et al.; 2011
- "PLoS One"; Thyroid hormones regulate selenoprotein expression and selenium status in mice. Mittag J, et al.; 2010
- "Journal of Immunology"; Selenoprotein k knockout mice exhibit deficient calcium flux in immune cells and impaired immune responses. Verma S, et al.; 2011
- U.C. Berkeley Wellness Letter: Selenium
- Linus Pauling Institute: Selenium
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