Magnesium is sold as a sleep aid almost everywhere. The truth is more precise: magnesium helps sleep most when your intake is low to begin with.
The mechanism is real
Magnesium is a cofactor in 300+ enzyme systems and contributes to normal functioning of the nervous system. It also binds to GABA receptors indirectly and regulates NMDA activity — plausibly relevant to sleep quality.
The human data
A 2012 double-blind RCT in elderly participants found magnesium supplementation improved subjective sleep time and sleep efficiency (Abbasi et al., J Res Med Sci). A broader 2021 systematic review (Mah et al., BMC Complementary Medicine) concluded that magnesium may improve subjective sleep measures in older adults, but evidence in younger, replete adults is thin.
Who is most likely to benefit
- People with low dietary magnesium: heavy caffeine or alcohol use, low vegetable/nut/whole-grain intake, or prolonged stress.
- Older adults, whose magnesium absorption declines with age.
Dosing notes
Supplemental forms differ: magnesium glycinate and citrate are absorbed reasonably well; oxide is cheap but poorly absorbed. The safe supplemental ceiling is 350 mg/day of elemental magnesium (US IOM) — higher doses can cause loose stools.
Sleep is governed by two systems: circadian rhythm (when you feel alert) and sleep pressure (how tired you feel). When these desynchronize, you get insomnia.