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.