Explain the Magnesium Deficiency and Toxicity?
Deficiency of magnesium is rare for two reasons: frstly, the mineral is widely distributed in the foods, secondly, kidney is able to adjust re-absorption of filtered magnesium to body needs. However, Mg depletion occurs in 'various conditions, which either inlpair its intestinal absorption or increase its urinary excretion. Studies have shown that a decline in urinary magnesium excretion during protein- energy malnutrition (PEM) is accompanied by a reduced intestinal absorption of magnesium. The catch-up growth associated with recovery from PEM is achieved only if magnesium supply is increased substantially. Most of the early pathological consequences of depletion are neurologic or neuromuscular defects, some of which probably reflect the influence of magnesium on potassium flux within tissues. Thus, a decline in magnesium status produces anorexia, nausea, muscular weakness, lethargy, staggering and if deficiency is prolonged, weight loss. Progressively increasing with the severity and duration of depletion are manifestations of hyperirritability, hyperexcitability, muscular spasms, and tetany, leading ultimately to convulsions.
An increased susceptibility to audiogenic shock is common in experimental animals. Cardiac arrhythmia and pulmonary oedema frequently have fatal consequences. It has been suggested that a suboptimal magnesium status may be a factor in the etiology of coronary heart disease and hypertension but additional evidence is needed. Hypomagnesernia associated with deficiency represents a plasma Mg levels of less than 1.5 mg/dl. It leads to impaismeilt in Ca and K homeostatsis. Hypocalcernia and hypokalemia have been observed in both experimentally produced and disease-related Mg deficiency. These disturbances are partially caused by hypomagnesemia induced changes in the production and function of PTH. Reduced serum Mg initially stimulates parathyroid gland to produce more PTH, but as deficiency becomes more severe, the sensitivity of parathyroid gland to slow serum Ca concentration is impaired and level of PTH .is low in relation to degree of hypocalcernia. Decreased Mg status has been suggested as a factor contributing to the pathogenesis of several chronic diseases. Both dysrhythmias and myocardial ischemia have been attributed to low Mg intakes. Hypomagnesemia in diabetes may be one of the risk factors in the development of diabetic retinopathy.