It is undoubtedly required for growth and maintenance but little is known about the quantitative need in man. Diets containing 0.25 to 0.3 mg. of magnesium daily, have maintained adults in balance (71). The body contains over 20 gm. of magnesium of which more than half is found in bone in combination with calcium and phosphorus. The remainder is present in soft tissues largely within the cells where it functions as a catalyst in a number of enzymatic reactions.

Magnesium deficiency has been observed in several species of animals, neuromuscular abnormalities and renal damage being prominent findings. Deficiency in man is not clearly defined although low levels of serum magnesium have been reported in many pathological conditions. Low magnesium concentration has been found in association with muscle twitching and convulsions but may be present without any characteristic symptoms. The normal value for serum magnesium varies with the method of determination. Flink (71) reports a mean value of 1.91 -!- 0.2 mEq/1 by the molybdivanadate method and 2.27 -1- 0.26 mEq/1 by the titan yellow method. Serum magnesium does not always reflect body stores of this substance just as serum potassium concentration may not be indicative of body content.

Depletion of body magnesium has been demonstrated in diabetic acidosis. Flink and associates reported magnesium deficiency in chronic alcoholism and in certain other chronic debilitating illnesses. Gross muscle tremor and delirium were common findings; muscular twitching, choreiform and athetoid movements and convulsions were encountered at times. Serum magnesium concentration was low in most instances. Administration of a magnesium salt appeared beneficial in a number of subjects who had the above findings. Response was dramatic in some instances but required several days in others.

The authors believe that the major manifestations of magnesium deficiency are related to cellular deficit. The pathogenesis of magnesium deficiency needs clarification although deficient intake during prolonged periods of parenteral feeding or in the course of prolonged alcoholic episodes are important factors. Aldosterone may have an influence as hypomagnesemia and negative magnesium balance has been found in primary aldosteronism.