A large meta-analysis has pooled the evidence on magnesium supplements. Published in Nutrients, the review combined 78 randomized controlled trials testing magnesium (Mg) against cardiometabolic risk factors — the cluster of measurements (weight, blood pressure, blood sugar, cholesterol, inflammation) that together predict heart disease and type 2 diabetes risk. Most of the trials used doses of 300 mg per day or more (79.5% of studies), and two-thirds ran for 12 weeks or longer.
The pooled results moved in a favorable direction across the board, but by small amounts. Compared with control groups, magnesium supplementation was linked to reductions in:
- Body weight: -0.70 kg (95% CI: -1.30 to -0.09)
- Systolic blood pressure: -2.50 mmHg (95% CI: -4.08 to -0.91)
- Diastolic blood pressure: -1.58 mmHg (95% CI: -2.50 to -0.65)
- Fasting blood glucose: -3.60 mg/dL (95% CI: -6.13 to -1.06)
- HbA1c (long-term blood sugar control): -0.15% (95% CI: -0.26 to -0.03)
- LDL ("bad") cholesterol: -3.21 mg/dL (95% CI: -5.27 to -1.15)
- Triglycerides: -9.24 mg/dL (95% CI: -16.87 to -1.61)
- Interleukin-6, a marker of inflammation: -1.10 pg/mL (95% CI: -1.93 to -0.27)
- Insulin resistance (HOMA-IR): -0.48 (95% CI: -0.79 to -0.18)
HDL ("good") cholesterol rose slightly, by 1.45 mg/dL (95% CI: 0.37 to 2.54).
Several markers did not move. The review found no significant effect on hip or waist circumference, body fat percentage, body mass index, total cholesterol, fasting insulin, liver enzymes, creatinine, or C-reactive protein. Magnesium, in other words, nudged several metabolic numbers without reshaping body composition.
Every number here is small on its own. A 2.5 mmHg drop in systolic blood pressure or half a kilogram of weight loss will not be something most people notice day to day. The authors themselves describe the clinical relevance of these changes as uncertain even though the statistical evidence for them is solid. The value of a meta-analysis like this is in ruling large effects in or out across a large pooled sample — not in promising a dramatic personal result.
A caveat on the evidence itself. Data on higher doses (500 mg/day and above) and longer interventions (25 weeks or more) remained limited, so it is not yet clear whether taking more, or taking it longer, would produce larger benefits or simply plateau.
Bottom line. In adults, 300 mg/day or more of magnesium for 12 weeks or longer was associated with small, statistically real improvements in blood pressure, blood sugar, cholesterol, and inflammation markers — worth knowing if you are already considering a magnesium supplement, but not a substitute for the larger effects of diet, exercise, and, where needed, medication.
Medical note. This article is for general educational purposes and should not be considered personal medical advice.