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Ingredient review

Magnesium

Description

What is it?

Magnesium (Mg) is an element and essential mineral. It is a cofactor in over three hundred enzymatic reactions involved in protein synthesis, muscle contraction, nerve function, blood pressure, glucose regulation, hormone receptor binding, cardiac conduction, transmembrane ion flux, and calcium channel gating. (72) It is required for the production of ATP, (48) and the synthesis of RNA and DNA. (72)

Not to be confused with: Manganese

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Main uses

Cardiovascular disorders
Gastrointestinal distress
Metabolic, endocrine, and hormonal disorders
Musculoskeletal disorders
Neurological disorders
Respiratory disorders
Sleep and fatigue

Formulations

Form
Absorption rate
Magnesium aspartate
~42-45% absorption (54)(64)
Magnesium lactate (90)
~42% absorption (23)(64)
Magnesium citrate (3)(90)
~30% absorption (45)(51)(64)(85)
Magnesium glycinate (81)
~24% absorption (64)(71)(87)
Magnesium chloride (6)(25)
~20% absorption (11)(52)(64)
Magnesium gluconate
~20% absorption (52)(57)(64)
Magnesium hydroxide (13)
~15% absorption (11)(24)(64) (11) (24) (64)
Magnesium sulfate (4)(9)
~4-7% (53)(64)(78)
Magnesium oxide (1)(2)
~4% absorption; ~23% in px with ileal resection (32)(64)(71)
Magnesium fumarate (64)
No absorption data
Magnesium orotate (80)
No absorption data
Magnesium pidolate (17)(29)
No absorption data
Magnesium pyrrolidone carboxylic acid (26)(27)
No absorption data

Dosing & administration

Adverse effects

While Mg is generally well-tolerated, oral supplementation may cause diarrhea, nausea, or vomiting. Intravenous overdose may cause thirst, hypotension, drowsiness, muscle weakness, respiratory depression, headaches, flushing, cardiac arrhythmia, coma, and death. (37)(47) There is no evidence of adverse effects from dietary sources. (43)

Pharmacokinetics

Absorption

  • Occurs in the ileum (56%), jejunum (22%), duodenum (11%), and colon (11%)
  • At low GI concentrations, Mg is uptaken through active transport via the saturable Transient Receptor Potential Channel Melastatin members TRPM6 and TRPM7. (89)
  • At high GI concentrations, Mg is absorbed primarily via passive paracellular transport. (70)

Distribution

  • After absorption, Mg is distributed to bone (53%), muscle (27%), soft tissues (27%), and blood (0.8%). (31)

Metabolism

  • In bone, Mg from the blood substitutes positions with the Mg in bone promoting, chondrocyte column development, osteoblast proliferation, and osteoclast activity. (18)
  • In the brain, Mg inhibits post-synaptic NMDA receptor excitation by increasing chloride uptake by GABA receptor stimulation, and by antagonizing calcium, reducing pre-synaptic glutamate release. (18)
  • In the heart and vascular system, Mg reduces ion channel activity in the myocardium, calcium availability and binding in cardiac muscle, and inflammation in the vascular system. Mg increases vasodilation. (18)
  • In muscle, Mg maintains the level of muscle contractility with calcium. (18)

Excretion

  • If not absorbed, Mg is eliminated in the feces (20-70%). (88)
  • If absorbed, Mg can be eliminated in the urine (5-70%). This can occur in the proximal tubules (10-30% via passive paracellular pathways), or the thick ascending limb (40-70% via claudin proteins, 5-10% via active TRPM6 transport). (89)
  • The half-life of Mg is approximately 1000 hours. (72)

References