Magnesium

Magnesium is the second most abundant cation in the human body. It is essential for several crucial metabolic reactions involving nucleic acid and protein synthesis, regulation of blood pressure, vasomotor tone, cardiac function, insulin regulation, bone metabolism, neuromuscular conduction, and nerve transmission. Magnesium is present largely in green leafy vegetables, nuts, and whole grains and less represented in meat, poultry, and fish. Total body magnesium is around 25 g, mostly in bones, muscles, and soft tissues. Magnesium is absorbed, with absorption influenced by several factors. The renal glomeruli filter magnesium, and most of it is reabsorbed in the tubules, with less than 5% excreted in urine. Magnesium deficiency may result from an inadequate diet, common in older adults; socioeconomic factors additionally increase risk. Several gastrointestinal disorders, renal disorders with magnesium wasting, alcoholism, and medications such as diuretics predispose to deficiency. Magnesium deficiency increases risk for accelerated bone loss, muscle disorders, ataxia, cramps, tetany, seizures, cardiac arrhythmias, tremors, depression, poor glycemic control, and possibly impaired cognition. Correction of deficiency is through a balanced diet and/or supplements while addressing the etiology. Hypermagnesemia does not result from excessive dietary intake. It usually results from excessive magnesium supplements taken in the presence of underlying chronic kidney disease. Hypermagnesemia can cause bradycardia, hypotension, loss of deep tendon reflexes, muscle paralysis, respiratory depression, and cardiac arrest.