The adult human contains 20 to 28 grams of total body magnesium. Approximately 60 % is found in bone, 26 % is associated with skeletal muscle and the balance is distributed between various organs and body fluids. Serum levels of Mg range from 1.5 to 2.1 mEq/L; it is second to K as an intracellular cation - half of the Mg, including most that is bound in the bone, is not exchangeable.

Magnesium is required for the production and transfer of energy for protein synthesis, for contractility of muscle and excitability of nerves, and as a cofactor in myriads of enzyme systems. AN EXCESS OF MG WILL INHIBIT BONE CALCIFICATION. Calcium and Mg have antagonistic roles in normal muscle contraction, calcium acting as the stimulator and Mg as the relaxer. An excessive amount of Ca can induce signs of Mg deficiency.

The rate of absorption of Mg ranges from 24 to 85 %. The lesser absorption rate is for metallic sources of Magnesium, the higher levels are associated with plant derived colloidal sources. Vitamin D has no effect on Mg absorption; the presence of fat, phytates and calcium reduces the efficiency of absorption. High performance athletes lose a considerable amount of Mg in sweat.

Deficiency Diseases of Magnesium

- Asthma
- Anorexia
- Menstrual migraines
- Growth failure
- ECG changes
- Neuromuscular problems
- Tetany (Convulsions)
- Depression
- Muscular weakness
- Muscle "Ties"
- Tremors
- Vertigo
- Calcification of small arteries
- Malignant' calcification of soft tissue

The RDA for Mg is 350mg/day for adult males, 300mg/day for adult females and 450 mg/day for pregnant and lactating females. If kidneys are healthy there is no evidence of toxicity at up to 6,000 mg per day.

Deficiencies of Mg result in a wide variety of deficiency diseases and symptoms.

Magnesium a major mineral nutrient. The body contains 20 to 28 g of magnesium; 40% is found in tissues like MUSCLE and 60% occurs in BONE and teeth, where it is combined with phosphate. Among soft tissues the liver and muscles contain the highest levels. Within cells magnesium is the second most prevalent type of positively charged ion (cation) after potassium. Magnesium is required for all major metabolic processes involving ATP, the chemical energy currency of the cell. Magnesium and magnesium-ATP complexes activate more than 300 enzymes. It functions in energy-consuming processes like biosynthesis of protein and of DNA and RNA; sugar breakdown (glycolysis); and ATP-dependent transport of materials into the cell. Magnesium is essential for the transmission of nerve impulses; for electrical potentials of cell membranes; muscle contraction; ATP formation; and maintenance of blood vessels.

Possible Roles in Maintaining Health

Magnesium is essential for normal calcium metabolism. In muscle contraction, magnesium balances the effects of calcium, which stimulates contraction. Thus magnesium regulates calcium uptake by cells to activate functions like heartbeat. Magnesium may also:

• protect against cardiovascular disease. It can help reduce high blood pressure, lower cholesterol as low-density lipoprotein (LDL) and increase HDL (high-density lipoprotein) cholesterol;

   

• protect against lead poisoning;

   

• protect against migraine and depression;

   

• help maintain normal heart function and prevent irregular heartbeat (cardiac dysrythmia); The imbalance
  between calcium and magnesium may increase the risk of
  cardiovascular disease, and magnesium deficiency increases the risk of severe disruptions of cardiac rhythm;

   

• help alleviate premenstrual syndrome, when used with zinc and vitamin B6 in certain cases;

   

• prevent kidney stones;

   

• alleviate preeclampsia and eclampsia, a syndrome in pregnancy characterized by high blood pressure and protein in the urine. In serious cases eclampsia can lead to convulsions and coma.

   

Magnesium Status and Health
Ivor E. Dreosti, PhD., D.Sc.

Nutrition Reviews, Vol. 53, No. 9

Magnesium is found in the body principally in the cells and the skeleton. Many biological processes are dependent on magnesium. Magnesium is involved in the functioning of more than 200 enzymes and the utilization of energy-rich ATP Not surprisingly, magnesium deficiency gives rise to a very broad syndrome, with symptoms including growth failure, pallor, weakness, tremor, muscle and nerve irritability, electromyographic changes, hypocalcemia, and hypokalemia.

Overall, nutritionists believe that the principal physiological functions of magnesium are known and can be met by the current world average Recommended Dietary Intake (RDI) of 4.5 mg/kg body weight per day. Indeed, it would seem that magnesium deficiency rarely occurs for purely dietary reasons. The condition, when it exists, is generally associated with gastrointestinal malabsorption, excessive fluid and electrolyte loss, renal dysfunction, general malnutrition associated with alcoholism, and several iatrogenic causes.

Nevertheless, a large number of research nutritionists strongly believe that many important aspects of magnesium deficiency remain to be recognized and evaluated, and that the condition occurs more widely than is currently recognized. The present review will concentrate on several aspects of these views.

Magnesium and Osteoporosis

In postmenopausal women loss of estrogen and the attendant lack of control of parathyroid hormone are important factors underlying the development of osteoporosis. Estrogen replacement, supplementation with calcium and vitamin D, or both, are widely applied prophylactic strategies with respect to osteoporosis, yet little attention is paid to the important involvement of magnesium in ensuring bone integrity.

Magnesium Status and Osteoporosis

Repeated studies have demonstrated that osteoporotic trabecular bone has significantly lower levels (12%) of magnesium than controls; these levels are similar to those that occur in magnesium deficiency. Dietary magnesium intakes have been reported to be lower (15%) in osteoporotic patients than in normal women, and markedly increased retention of magnesium (up to 90%) has been noted in osteoporotic postmenopausal women following a parenteral magnesium load. Serum magnesium levels are often slightly reduced, but red blood cell magnesium appears to be significantly lower in osteoporotic patients.

Magnesium in the Treatment of Osteoporosis

Several recent studies have reported on magnesium supplements in the treatment of osteoporosis-with favorable results. In a group of postmenopausal women in Israel suffering from osteoporosis who received magnesium supplements in the range 250-750 mg/day for 24 months, either trabecular bone density increased (up to 8%) or bone loss was arrested (in 87%); in some cases both an increase in bone density and arrested bone loss occurred. Untreated controls, on the other hand, lost bone density at an average of I % a year. Similarly, a group of postmenopausal osteoporotic patients in Czechoslovakia who received magnesium at levels ranging from 1500 to 3000 mg of magnesium lactate per day for 2 years. Nearly 65% were classified totally free of pain and with no further deformity of vertebrae, with the condition in the remainder either arrested or slightly improved.

Magnesium and Heart Disease

Much has been written over the last decade in relation to magnesium and heart disease. At pharmacological levels there is some evidence that infusion of magnesium ions may help in the treatment of cardiac arrhythmia, possibly due to its role as a physiological calcium blocker. Several epidemiological studies with humans and experiments with animals suggest a degree of protection associated with replete magnesium status with respect to atherogenesis. In addition, a limited number of experimental studies with humans point to an improved blood lipid profile in patients supplemented with dietary magnesium. Most recently, studies with rats have indicated that dietary magnesium deficiency increases the susceptibility of lipoproteins and tissues to peroxidation, which suggests that the mechanism responsible for the pathology associated with several aspects of magnesium deficiency may involve lipid peroxidation.

Magnesium Requirements

The adult Recommended Dietary Allowance (RDA) for magnesium is 350 mg per day for men and 280 mg for women. The typical American diet provides about 120 mg per 1,000 calories. Thus a person consuming 1,500 calories or less is likely to be magnesium deficient. Factors that increase the need for magnesium due to limited uptake or increased losses include high dietary fiber; too much phosphate (as soft drinks) and alcoholic beverages; high psychological stress; some diuretics (water pills) and regular, strenuous exercise. Excessive calcium in supplements may compete with magnesium. Diseases and conditions that cause magnesium depletion include malabsorption, malnutrition, alcoholism and intravenous feeding using nutrient mixtures that do not contain enough magnesium. Marginal deficiency is very common among teenagers and people who diet; diabetics; pregnant and lactating women; those who drink heavily; elderly persons with poor eating habits; those taking diuretics and digitalis; athletes; women with osteoporosis; and individuals with severe kidney disease and severe diarrhea.

Early symptoms of magnesium deficiency, including a loss of appetite, upset stomach and diarrhea, are vague, making diagnosis of a mild deficiency difficult. Symptoms of long-term deficiency relate to the nervous system: confusion, apathy, depression, irritability, irregular heartbeat, muscle weakness, tremors, convulsions and poor coordination, as well as a lack of appetite, listlessness, nausea and vomiting. Measurement of white blood cell magnesium can be used to help assess the nutritional status of this mineral.

Reference:http://www.dcnutrition.com/minerals/Detail.CFM?RecordNumber=70