Magnesium Deficiency: A Cause of Heterogenous Disease in Humans

Extract

INTRODUCTION

Magnesium is the most prevalent intracellular divalent cation and the second most prevalent cation in the body.^(1,2) The normal adult body content is ∼25 g and its distribution is approximately equally divided between the skeleton and soft tissues.⁽³⁾ A large proportion (about one‐third) of skeletal magnesium (Mg) resides on the surface of bone. Because this fraction is surface exchangeable and because the skeletal Mg level falls during Mg depletion, it is hypothesized that this component serves as a reservoir to maintain the extracellular Mg concentration.⁽⁴⁾ Extracellular Mg accounts for only 1% of total body Mg. In the plasma, 55% of Mg is ionized, or free, 15% is complexed to anions, and the rest (∼30%) is bound to protein (chiefly albumin).^(2,3) Mg is contained within all intracellular compartments. It is principally bound to ATP (80–90%) and other negatively charged molecules.⁽⁵⁾ Total cellular Mg ranges from 5–20 mM; the greater the metabolic activity of a cell, the greater the Mg content. Intracellular free Mg²⁺ accounts for about 1–5% of total cellular Mg (0.2–1.0 mM).⁽⁶⁾ Mg is actively transported into and out of cells and is influenced by various hormonal and pharmacological factors which perhaps regulate the intracellular Mg²⁺ concentration and hence activity of Mg‐sensitive enzymes.^(6–8) For example, insulin has been shown to increase intracellular Mg in a number of tissues including skeletal and cardiac muscle, uterine smooth muscle, red blood cells, platelets, and lymphocytes (for review see Refs. 9 and 10).