Sources: Almost all of our magnesium supplies come from the vegetable kingdom, though seafood has fairly high amounts. As a component of chlorophyll, this mineral is important to plant photosynthesis; therefore, the dark green vegetables are good sources of magnesium. Most nuts, seeds, and legumes have high amounts of magnesium; soy products, especially soy flour and tofu, and nuts such as almonds, pecans, cashews, and brazil nuts are good examples. The whole grains, particularly wheat (especially the bran and germ), millet, and brown rice, and fruits such as avocado and dried apricot are other sources. Hard water can also be a valuable source of magnesium. Dolomite and bonemeal are good sources of magnesium, as they are of calcium.

Many factors affect magnesium availability from foods. One is the amount of magnesium in the soil in which the food is grown. Much magnesium can be lost in the processing and refining of foods and in making oils from the magnesium-rich nuts and seeds. Nearly 85 percent of the magnesium in grains is lost during the milling of flours. Soaking and boiling foods can leach magnesium into the water, so the "pot liquor" from cooking vegetables may be high in magnesium and other minerals. Oxalic acid in vegetables such as spinach and chard and phytic acid in some grains may form insoluble salts with magnesium, causing it to be eliminated rather than absorbed. For these reasons and those previously discussed, many people get insufficient magnesium from their diets.

Functions:Magnesium is considered the "antistress" mineral. It is a natural tranquilizer, as it functions to relax skeletal muscles as well as the smooth muscles of blood vessels and the gastrointestinal tract. (While calcium stimulates muscle contraction, magnesium relaxes them.) Because of its influence on the heart, magnesium is considered important in preventing coronary artery spasm, a significant cause of heart attacks. Spasms of the blood vessels lead to insufficient oxygen supply through them and pain, injury, or death of the muscle tissue that they nourish. To function optimally, magnesium must be balanced in the body with calcium, phosphorus, potassium, and sodium chloride. For example, with low magnesium, more calcium flows into the vascular muscle cells, which contracts them-leading to tighter vessels and higher blood pressure. Adequate magnesium levels prevent this.

Magnesium, like potassium, is primarily an intracellular nutrient. It activates enzymes that are important for protein and carbohydrate metabolism, and it is needed in DNA production and function. Magnesium also modulates the electrical potential across cell membranes, which allows nutrients to pass back and forth. It helps in the release of energy by transferring the key phosphate molecule to adenosine triphosphate (ATP), an energy source generated by the cytochrome system.

In summary, even though it is not as prevalent as the other macrominerals, magnesium has many essential metabolic functions in the body. It is important in the production and transfer of energy, in muscle contraction and relaxation, in nerve conduction, in protein synthesis, and in many biochemical reactions as a cofactor to enzymes. Magnesium is also thought to dilate the blood vessels.

Uses: As time goes on, magnesium is recommended and used in more and more treatments. Prevention or treatment of myocardial infarctions (MIs), prevention of kidney stones, and in treatment of premenstrual syndrome are some important recent uses. Magnesium has been used with some success in relieving certain kinds of angina and reducing the risks of coronary artery spasms, which can lead to angina or, more severely, heart attack. Deficient magnesium levels have been found in the blood and hearts of cardiac victims. Besides preventing heart attacks, magnesium has a mild effect on lowering blood pressure and so is used to treat and prevent hypertension and its effects. Magnesium supplementation can reduce many of the symptoms of mitral valve prolapse, such as palpitations or arrhythmias, and it may help in other cardiac arrythmias such as atrial tachycardia or fibrillation, or those caused by taking excess digitalis, a cardiac drug. It may also reduce the bronchoconstriction in asthma by relaxing the muscle around the bronchial tubes. Intravenous solutions containing magnesium and other nutrients have been used successfully to break acute asthma attacks.