Magnesium
Summary
An essential mineral involved in ATP metabolism, muscle function, and nerve signaling. Deficiency correction is well supported; evidence for sleep and cardiovascular benefits from supplementation is preliminary and largely observational.
Mechanism
Magnesium is a cofactor for over 300 enzymatic reactions, central to ATP metabolism, muscle contraction and relaxation, nerve transmission, and vascular tone. Mg2+ is a physiological NMDA-receptor blocker and supports GABA signaling, which links it to neuromuscular calm and sleep physiology.
Reported effects
Ratings are relative to peers in the same category, not absolute claims.
Studied dosing — research context
Most supplementation trials use 200-400 mg of elemental magnesium per day; 500 mg/day was used in the insomnia RCT. Different salt forms (citrate, glycinate, oxide) differ in elemental content and tolerability. These are doses used in research, not guidance.
Research context only. This is not a recommendation.
Safety
Diarrhea and loose stools occur at higher doses (an osmotic effect). People with impaired kidney function are at risk of hypermagnesemia because they cannot excrete excess magnesium efficiently.
Limitations
Serum magnesium reflects roughly 1% of total body magnesium and is a poor status marker, so deficiency is often clinically invisible. Most chronic-disease evidence is observational, and the sleep evidence rests largely on one small 2012 RCT — a later systematic review judged the evidence quality substandard for firm conclusions.