Study Title:

Effect of Magnesium Supplementation on Blood Pressure

Study Abstract

To date, there has been inconclusive evidence regarding the effect of magnesium supplements on blood pressure (BP). This meta-analysis was conducted to assess the effect of magnesium supplementation on BP and to establish the characteristics of trials showing the largest effect size. Primary outcome measures were systolic blood pressure (SBP) and diastolic blood pressure (DBP) at the end of the follow-up period. One hundred and forty-one papers were identified, of which 22 trials with 23 sets of data (n=1173), with 3 to 24 weeks of follow-up met the inclusion criteria, with a supplemented elemental magnesium range of 120-973 mg (mean dose 410 mg). 95% confidence intervals (CI) were calculated using DerSimonian and Laird's random-effects model, with effect size calculated using Hedges G. Combining all data, an overall effect of 0.36 and 0.32 for DBP and SBP, respectively, was observed (95% CI 0.27-0.44 for DBP and 0.23-0.41 for SBP), with a greater effect being seen for the intervention in crossover trials (DBP 0.47, SBP 0.51). Effect size increased in line with increased dosage. Although not all individual trials showed significance in BP reduction, combining all trials did show a decrease in SBP of 3-4 mm Hg and DBP of 2-3 mm Hg, which further increased with crossover designed trials and intake >370 mg/day. To conclude, magnesium supplementation appears to achieve a small but clinically significant reduction in BP, an effect worthy of future prospective large randomised trials using solid methodology.

From press release:

Researchers from the University of Hertfordshire have found that magnesium supplements may offer small but clinically significant reductions in blood pressure. In a paper published in the European Journal of Clinical Nutrition, the researchers also discovered that the size of the effect increased in line with increased dosage.

Cardiovascular diseases cause almost fifty per cent of deaths in Europe and contribute significantly to escalating healthcare costs. Elevated blood pressure or hypertension is a major risk factor for mortality from cardiovascular and renal disease. Causes of hypertension include (but are not limited to) smoking, sedentary lifestyle, a diet high in sodium and an inadequate intake of other minerals such as potassium, calcium and magnesium.

"Until now, there's been inconclusive evidence regarding the effect of magnesium supplements on blood pressure," said Lindsy Kass, Senior Lecturer and registered nutritionist at the University of Hertfordshire. "So we conducted a meta-analysis by analysing data from twenty-two trials involving 1,173 people to assess the effect of magnesium on blood pressure."

In the trials, the magnesium supplementation doses ranged from 120 to 973 mg with between 3 to 24 weeks of follow-up. Although not all individual trials showed significance in blood pressure reduction, by combining the trials, the overall data indicated that magnesium supplementation reduced both systolic and diastolic blood pressure. With the best results observed at the higher dosages.

"The clinical significance in the reductions found from this meta-analysis may be important in helping to prevent hypertension and associated risks around cardiovascular disease," said Lindsy. "And is worthy of future trials using solid methodology."

Study Information

Kass L, Weekes J, Carpenter L.
Effect of magnesium supplementation on blood pressure: a meta-analysis.
Eur J Clin Nutr.
2012 April
School of Life Sciences, University of Hertfordshire, Hatfield, UK.

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