Thirty-one published papers carried out in 29 different populations. Two papers reported findings from the same data-set and are combined in the results. Three studies were prospective, 24 cross-sectional, of which 4 also included a longitudinal component, and two were from baseline data in a trial. Sample size of each study ranged from 40 to 58 218, and the total number of subjects examined by the studies was 118265.
Twelve papers reported some comparison between magnesium intake and BP subgroups without a regression or correlation estimate. Seven of these 12 studies reported a negative association between magnesium intake and BP and five reported no association.
A total of 46 subgroup analyses from 18 studies reported either a regression or a Pearson-r correlation co-efficient of magnesium intake to BP. A negative association between magnesium intake and BP was reported from simple regression-correlation analysis in 15 or 16 subgroups for systolic BP (SBP)and in 14 out of 17 for diastolic BP (DBP), and significant negative association were found in 4 and 6 studies respectively. In studies that adjusted for confounding factors, a negative association was reported in 18 of 26 sub-groups for SBP and 16 of 24 for DBP, this association was significant in 9 and 8 studies respectively. One positive association was reported for SBP and 3 for DBP on simple regression correlation analysis and 8 for SBP and 8 for DBP on multiple regression correlation analysis. One significant positive association was reported.