Magnesium Supplementation and Blood Pressure

A Cochrane review 1 [Abstract] included 12 studies with a total of 545 subjects with raised systolic blood pressure (SBP) HASH(0x2f82cc8)140 mmHg or diastolic blood pressure (DBP) HASH(0x2f82cc8)85 mmHg. Combining all trials, participants receiving magnesium supplements as compared to control did not significantly reduce SBP (MD -1.3 mmHg, 95% CI -4.0 to 1.5, I² =67%), but reduced statistically significantly DBP (MD -2.2 mmHg, 95% CI -3.4 to -0.9, I² =47%).

A meta-analysis 2 included 22 studies with a total of 1 173 subjects. Supplemented elemental magnesium range was 120-973 mg (mean dose 410 mg=16.9 mmol), and the duration of treatment with magnesium ranged from 3 to 24 weeks, with a mean duration of 11.3 weeks. Effect size was calculated using Hedges G. Combining all data, an overall effect of 0.36 (95% CI 0.27 to 0.44) for DBP and 0.32 (95% CI 0.23 to 0.41) for SBP was observed. These effect sizes translate to an actual reduction of 2-3 mm Hg for DBP and 3-4 mm Hg for SBP. When a subanalysis for dosage was carried out (<370 mg Mg and HASH(0x2f82cc8)370 mg Mg/day), results for both SBP and DBP showed greater efficacy at the higher dose (effect size for DBP 0.66, 95% CI 0.51 to 0.82 and for SBP 0.70, 95% CI 0.56 to 0.89).

Comment: The quality of evidence is downgraded by inconsistency (variability in results).

References

• Dickinson HO, Nicolson DJ, Campbell F, Cook JV, Beyer FR, Ford GA, Mason J. Magnesium supplementation for the management of essential hypertension in adults. Cochrane Database Syst Rev 2006 Jul 19;3:CD004640. [PubMed]
• Kass L, Weekes J, Carpenter L. Effect of magnesium supplementation on blood pressure: a meta-analysis. Eur J Clin Nutr 2012;66(4):411-8. [PubMed]