Almost all foods contain sodium. Most of the sodium in our diets is added during food processing, during cooking, and at mealtimes. The American Heart Association recommends that all people limit their sodium intake to no more than 2.4 grams per day. (The Upper Level set by the Food and Nutrition Board is 2300 milligrams per day.) Still, sodium is essential to maintenance of normal fluid balance throughout the body and to normal nerve impulse conduction. If sodium intake is inadequate, muscle weakness, headache, irritability, and confusion will occur.
The mineral selenium is a cofactor for the activity of the enzyme glutathione peroxidase. This enzyme participates in a system that metabolizes peroxides into less toxic alcohol derivatives and water. Peroxides tend to become free radicals, which in turn can attack and break down cell membranes, causing cell damage. Selenium is considered to be important in protecting heart cells and other cells against oxidative damage. In addition, because it reduces the amount of free radical damage to cells, selenium may be important in protecting against cancer.
