The effect is not great, but magnesium supplements are relatively cheap and safe. Excessive magnesium blood levels are prevented by healthy kidneys. If you have kidney impairment, you might develop magnesium toxicity when you take a supplement. Even if magnesium supplementation reduces average systolic blood pressure by only 2 points, half of supplementers will see a drop over 2 points.
“Magnesium supplementation leads to decreases in blood pressure among both hypertensive and normotensive adults, according to the findings of a meta-analysis.Taking 368-mg magnesium per day for 3 months led to 2.00 mm Hg reductions in systolic blood pressure (95% CI 0.43-3.58) and 1.78 mm Hg reductions in diastolic blood pressure (95% CI 0.73-2.82), Yiqing Song, MD, ScD, of the Indiana University School of Public Health in Indianapolis, and colleagues reported in a meta-analysis of 34 separate trials, published online in Hypertension.
“Our findings indicate a causal effect of magnesium supplementation on lowering blood pressures in adults,” the researchers concluded. “Our findings suggested that oral magnesium supplements can be recommended for the prevention of hypertension or as adjuvant antihypertensive therapy, although future rigorously designed randomized controlled trials with blood pressure assessment as primary outcomes are warranted to yield confirmatory evidence.”