Magnesium is a mineral that is needed by every cell of the body. Magnesium is needed for bone, protein, and fatty acid formation, making new cells, activating B vitamins, relaxing muscles, clotting blood, and forming ATP - the muscle's energy source.
About half of the body's magnesium stores are found inside cells of body tissues and organs, and half are combined with calcium and phosphorus in bone. Only 1 percent of the magnesium in the body is found in blood. Dietary sources of magnesium include green vegetables such as spinach, as well as nuts, seeds, and some whole grains.
The magnesium content of refined foods is usually low. Whole-wheat bread, for example, has twice as much magnesium as white bread because the magnesium-rich germ and bran are removed when white flour is processed.
Interestingly, calcium and magnesium compete for absorption and too much calcium in the diet blocks magnesium absorption. For this reason, combined calcium / magnesium supplements should contain approx. a 2:1 calcium / magnesium ratio for the greatest effectiveness. As magnesium can have strong laxative effects (and is a common ingredient in laxative products), it is often used to remedy constipation.
Magnesium supplements are available in capsules and tablets, and are commonly used to improve sleep and to relieve anxiety.