A good food source of magnesium contains a substantial amount of magnesium in relation to its calorie content and contributes at least 10 percent of the U.S. Recommended Dietary Allowance (U.S. RDA) for magnesium in a selected serving size. The U.S. RDA for magnesium is 400 milligrams per day. (The U.S. RDA given is for adults, except pregnant or lactating women, and children over 4 years of age.) The U.S. RDA for magnesium is the amount of the mineral used as a standard in nutrition labeling of foods. This allowance is based on the 1968 Recommended Dietary Allowances (RDA) for 24 sex-age categories set by the Food and Nutrition Board of the National Academy of Sciences. The 1989 RDA has been set at 280 milligrams per day for women 19 to 50 years of age and 350 milligrams for men 19 to 50 years of age Magnesium (Mg) is a trace mineral that is known to be required for several hundred different functions in the body. A significant portion of the symptoms of many chronic disorders are identical to symptoms of magnesium deficiency. Studies show many people in the U.S. today do not consume the daily recommended amounts of Mg. A lack of this important nutrient may be a major factor in many common health problems in industrialized countries. Common conditions such as mitral valve prolapse, migraines, attention deficit disorder, fibromyalgia, asthma and allergies have all been linked to a Mg deficiency. Perhaps, not coincidentally, these conditions also tend to occur in clusters together within the same individual. A magnesium deficiency as a root cause would provide a logical explanation of why some people suffer from a constellation of these types of problems.