1. ¹Department of Epidemiology and Disease Control, Yonsei University Graduate School of Health Science and Management, Seoul, South Korea
2. ²Welch Center for Prevention, Epidemiology and Clinical Research Seoul, South Korea
3. ³Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
4. ⁴Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA

Correspondence: Dr. Edgar R. Miller III, Welch Center for Prevention, Epidemiology & Clinical Research, The Johns Hopkins Medical Institutions, 2024 E. Monument Street, Suite 2-600, Baltimore, MD 21205-2223, USA. E-mail: ermiller@welch.jhu.edu

^*This study was supported by a research fellowship grant from the Four Schools Physician–Scientist Program (VKS), grants from the NIH NIDDK (MJK) K24 DK02856 and NHLBI K08 HL03857 (ERM).

Received 26 December 2001; Accepted 26 March 2002.

Abstract

Background An increased intake of magnesium might lower blood pressure (BP), yet evidence from clinical trials is inconsistent, perhaps as a result of small sample size or heterogeneity in study design.

Methods: We performed a meta-analysis of randomized trials that tested the effects of magnesium supplementation on BP. Twenty trials meeting the inclusion criteria were identified. Random effects models and meta-regression methods were used to pool study results and to determine the dose–response relationship of magnesium to BP.

Results: The 20 studies included 14 of hypertensive and 6 of normotensive persons totaling 1220 participants. The doses of magnesium ranged from 10 to 40 mmol/day (median, 15.4 mmol/day). Magnesium supplementation resulted in only a small overall reduction in BP. The pooled net estimates of BP change (95% confidence interval [CI]) were -0.6 (-2.2 to 1.0) mm Hg for systolic BP and -0.8 (-1.9 to 0.4) mm Hg for diastolic BP. However, there was an apparent dose-dependent effect of magnesium, with reductions of 4.3 mm Hg systolic BP (95% CI 6.3 to 2.2; P < .001) and of 2.3 mm Hg diastolic BP (95% CI 4.9 to 0.0; P = .09) for each 10 mmol/day increase in magnesium dose.

Conclusions: Our meta-analysis detected dose-dependent BP reductions from magnesium supplementation. However, adequately powered trials with sufficiently high doses of magnesium supplements need to be performed to confirm this relationship.