Magnesium vs Vitamin D
Both are commonly discussed for focus & cognition and mood and inflammation and energy and immune health. Magnesium and Vitamin D both have moderate evidence — Magnesium edges ahead on research volume (20 vs 20 studies referenced).
Evidence last reviewed May 2026
Magnesium recommends stacking with Vitamin D: Magnesium is required as a cofactor for vitamin D metabolism and activation; deficiency in one can blunt the effects of the other
Vitamin D recommends stacking with Magnesium: Magnesium is a cofactor required for vitamin D metabolism and conversion to its active form; deficiency in magnesium may blunt the response to vitamin D supplementation.
Evidence
🟡Moderate Evidence
🟡Moderate Evidence
Research says
Research agrees
Partially supported
Expert mentions
315
4 recommend
245
3 recommend
Studies
20
referenced
20
referenced
Study dose
200–400mg
Studies and expert sources consistently reference 200–400 mg of elemental magnesium daily; the required capsule dose varies significantly by form, as elemental magnesium content differs — for example, magnesium glycinate is roughly 14% elemental magnesium, meaning a 400 mg capsule delivers only ~56 mg elemental magnesium.
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Best timing
EveningWith food
MorningWith food
Who recommends
Caution
Generally safe
Generally safe
Magnesium
Key findings
- ·A strong-quality meta-analysis found oral magnesium supplementation improved sleep outcomes in older adults with insomnia, partially supporting claims about magnesium's role in sleep quality and onset.
- ·A strong-quality meta-analysis found magnesium supplementation positively affected glucose metabolism parameters in people with or at risk of type 2 diabetes, suggesting metabolic benefits in at-risk populations.
- ·Moderate-quality reviews support a role for magnesium in migraine prevention and in cardiovascular and cardiometabolic health, though causality and effect sizes require further confirmation.
Evidence gaps
- ·Most evidence comes from older adults or clinically deficient populations; it remains unclear whether magnesium supplementation benefits healthy individuals with adequate baseline magnesium levels.
- ·Form-specific clinical outcome data (e.g., glycinate, threonate, malate) is largely absent from high-quality trials, making it impossible to definitively recommend one form over another for specific outcomes like sleep or cognition.
Vitamin D
Key findings
- ·A strong-quality meta-analysis supports combined calcium and vitamin D supplementation for reducing osteoporosis risk in postmenopausal women.
- ·A single moderate-quality RCT (D-Health trial) found limited evidence that vitamin D supplementation significantly reduces major cardiovascular events.
- ·One moderate-quality RCT found vitamin D supplementation was associated with higher testosterone levels in men, but this has not been sufficiently replicated.
Evidence gaps
- ·No studies in this review directly tested health outcomes at the specific serum vitamin D range of 60–80 ng/mL, leaving expert claims about optimal target levels unsupported by the current evidence base.
- ·The testosterone finding comes from a single moderate-quality RCT; additional well-powered replication trials are needed before this can be considered an established benefit.