Chronically low dietary selenium is associated with an increased risk for cancer, heart disease, and low immune function. Severe selenium deficiency is associated with a heart disorder called Keshan disease. Prolonged dosages of 900 micrograms or more per day can cause symptoms of selenium toxicity. Symptoms of selenium toxicity include nervousness, depression, nausea and vomiting, emotional instability, a garlic odor of the breath and sweat, and in severe cases, loss of hair and fingernails. The selenium content of food is directly related to the amount of selenium in the soil in which the food was grown.
Some selenium is lost when foods are washed, cooked, or processed.
Refining grains reduces selenium content by 50 to 75 percent, and boiling by 45 percent. Selenium Content of Selected Foods, in Micrograms per 3 oz. Rodale Press, 1996. Hendler, S. The Doctor s Vitamin and Mineral Encyclopedia. Janson, M. The Vitamin Revolution.