Does magnesium help with blood pressure?

Large cross-sectional studies have shown that a higher systolic blood pressure in adults who experience hypertensive crises (sudden and severe rises in blood pressure) is associated with a higher serum magnesium concentration.^[1] However, in healthy children and adults without hypertensive crises, higher blood pressure is associated with a lower serum magnesium concentration.^[2][3][4] Furthermore, children with lower serum magnesium concentrations are more likely to have high blood pressure,^[2][3] and serum magnesium concentrations are lower in adults with high blood pressure (hypertension) compared to healthy adults.^[4]

Other types of observational studies show that a lower systolic blood pressure is associated with a high dietary magnesium intake^[4][5] and that people with a high dietary magnesium intake are less likely to have high blood pressure (hypertension).^[6] However, not all studies confirm this relationship,^[7] and these types of studies have limitations because magnesium intake is estimated from self-reported diet intake surveys. Consequently, they do not reveal whether supplementation with magnesium helps with blood pressure.

Meta-analyses of randomized controlled trials show that supplementation with magnesium can have a small but meaningful effect on lowering blood pressure in people with high blood pressure,^{[8][9][10][11]} prediabetes,^[12] or type 2 diabetes.^[13][14] However, there is large between-trial variability in the effect size, and the efficacy of magnesium on blood pressure appears greatest in people with low serum magnesium concentrations.^[15][9] That said, many randomized controlled trials do not report baseline serum magnesium concentrations, so this relationship requires further exploration.