Magnesium

Magnesium is one of the most studied minerals in human nutrition, functioning as a cofactor in over 300 enzymatic reactions. Population surveys consistently show a significant proportion of adults in the U.S. consume below the Estimated Average Requirement (EAR) for magnesium, suggesting inadequate dietary intake is common. The strongest evidence for magnesium supplementation relates to sleep quality. A randomized trial (Abbasi et al., 2020, n=46) in older adults found 500 mg/day for 8 weeks significantly improved sleep efficiency, sleep time, and early morning awakening as measured by validated scales. An earlier small RCT (Held et al., 2002, n=12) found magnesium reduced cortisol, ACTH, and improved slow-wave sleep in elderly subjects. Notably, most sleep studies have focused on older adults or those with suspected deficiency — benefits in younger, replete populations are less established. Evidence for anxiety and depression is moderate and growing. A 2017 RCT (Tarleton et al., n=126) found magnesium chloride (248 mg elemental/day) reduced PHQ-9 depression and anxiety scores significantly compared to an active control over 6 weeks. Effect sizes were comparable to antidepressants in this mild-to-moderate population. However, the open-label design (no blinding) limits confidence in these findings. Mechanistically, magnesium modulates NMDA receptors and may influence GABA-A receptor function — pathways relevant to anxiety and mood — though translation from mechanism to clinical effect requires cautious interpretation. For athletic performance, evidence is mixed. Magnesium requirements increase with physical activity, and deficiency is associated with impaired muscle function and recovery. Supplementation in deficient athletes may improve performance, but effects in already-replete individuals are less clear. The specific advantages of different magnesium forms (glycinate, threonate, malate, citrate) have limited head-to-head RCT comparison. Safety profile is generally favorable at doses up to the Tolerable Upper Intake Level (UL) of 350 mg/day from supplements (additional dietary magnesium is not included in this UL). The most common side effect is diarrhea/GI upset, particularly with oxide and citrate forms. Individuals with kidney disease should consult a healthcare provider before supplementing.