Magnesium

Magnesium (Mg2+) is the second most abundant intracellular cation, the fourth most abundant cation in the human body, and an essential cofactor in more than 600 enzymatic reactions encompassing DNA and RNA synthesis, protein synthesis, cellular energy metabolism, ion channel regulation, and neuromuscular function. Total body magnesium in the adult human is approximately 24 to 29 grams, of which approximately 60 percent resides in bone mineral, 39 percent in intracellular soft tissue compartments, and less than 1 percent in extracellular fluid and plasma. Serum magnesium concentration in healthy adults is maintained within a narrow physiological range of 0.75 to 0.95 millimoles per liter through coordinated intestinal absorption, renal reabsorption, and osseous exchange, with the transient receptor potential melastatin channels TRPM6 and TRPM7 serving as the principal apical magnesium entry pathways in intestinal and renal epithelial cells. The molecular pharmacology of magnesium is anchored by its voltage-dependent block of the N-methyl-D-aspartate (NMDA) receptor ion channel, a mechanism through which extracellular Mg2+ occupies a binding site within the channel pore at resting membrane potential and is expelled upon postsynaptic depolarization, thereby gating calcium influx and serving as a coincidence detector for synaptic plasticity. This NMDA receptor interaction, together with magnesium's roles as a physiological calcium antagonist, a modulator of potassium and sodium channel conductance, and a required cofactor for ATP-dependent kinase and phosphatase reactions, underlies the broad clinical pharmacology of the element across neurological, cardiovascular, musculoskeletal, and metabolic systems. Subclinical magnesium deficiency is increasingly recognized as a prevalent and underdiagnosed condition, with epidemiological surveys indicating that approximately 50 to 80 percent of adults in industrialized nations consume less than the estimated average requirement. The clinical consequences of chronic marginal magnesium status include increased risk of hypertension, type 2 diabetes mellitus, metabolic syndrome, coronary artery disease, stroke, migraine, depression, and osteoporosis. The tolerable upper intake level for supplemental magnesium from nonfood sources is set at 350 milligrams per day for adults by the United States Institute of Medicine, though this threshold is under active re-evaluation in light of accumulating evidence that higher supplemental intakes are well tolerated in individuals with normal renal function. Magnesium is available in numerous supplemental salt forms that differ substantially in elemental magnesium content, solubility, bioavailability, and tissue distribution. Organic salts (citrate, glycinate, taurate, malate, threonate) demonstrate superior bioavailability compared to inorganic forms (oxide, hydroxide, carbonate, sulfate) in human pharmacokinetic studies. Magnesium L-threonate has attracted particular research interest for its capacity to elevate brain magnesium concentrations through blood-brain barrier penetration via glucose transporters, with randomized controlled trials demonstrating significant improvements in cognitive performance and working memory. This monograph documents the chemical identity, discovery history, molecular pharmacology, pharmacokinetics across supplemental forms, preclinical and clinical evidence base, sourcing and quality verification, reconstitution and handling, stack interactions, adverse event profile, and a comparative assessment of five magnesium salt forms against five competency standards. The compound is generally recognized as safe at recommended supplemental doses in individuals with normal renal function; dose adjustment or avoidance is indicated in moderate to severe renal impairment.