Magnesium Depletion During Prolonged Fasting of Obese Males

Abstract

Prolonged fasting is associated with a continued magnesium excretion. After 2 months of fasting the actual deficit may reach 20% of the total body magnesium content in some subjects. Most of the loss occurs via the kidney but in some subjects the intestine functions as an additional excretory organ for magnesium throughout fasting. The magnesium content of muscle after fasting may be 20% below normal, but the over-all magnesium deficit was greater in some subjects than could be accounted for by lean tissue depletion alone. Despite evident muscle depletion, the concentration of magnesium in plasma remained unchanged. The excess acid load presented for excretion in the urine and the absence of carbohydrate intake might be factors contributing to the persistent loss of magnesium. The magnitude of magnesium excretion parallels the severity of the acidosis and ingestion of glucose brings about a decrease of magnesium loss. No definite evidence could be obtained that magnesium depletion precipitates tetanic muscle spasm occasionally observed in prolonged fasting.