The Effect of the Mediterranean Diet on Hypertension: A Systematic Review and Meta-Analysis

Abstract

Objective: The adoption of a Mediterranean diet (MD) pattern of eating is often described as a strategy to help prevent or manage hypertension. However, this dietary regimen has not been reviewed systematically for its efficacy against hypertension. Therefore, the purpose of this study was to analyze the effect of interventions of at least 1 year duration on blood pressure (BP) values through a systematic review and meta-analysis. The focus was on interventions comparing an MD with a low-fat diet.Design: The authors accessed and searched PubMed and Scopus databases up to March, 2015. Randomized control trials comparing MD vs low-fat diet were included. The researchers assessed the methodological quality, extracted the valid data, and conducted the meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines.Results: Six trials (more than 7,000 individuals) were identified. Meta-analysis showed that interventions aiming at adopting an MD pattern for at least 1 year reduced both the systolic BP and diastolic BP levels in individuals with normal BP or mild hypertension. The effect was higher for the systolic BP (-1.44 mm Hg) but also consistent for the diastolic BP (-0.70 mm Hg). However, the results have to be interpreted with caution owing to the reduced number of studies eligible for inclusion in this meta-analysis. This situation limited the statistical power of the analyses. Furthermore, in all analyses, the pooled effect estimation showed a high evidence of heterogeneity, which compromises the validity of the pooled estimates.Conclusions and Implications: A positive and significant association was found between the MD and BP in adults. However, in all cases the magnitude of the effect was small. Based on this limited group of studies and their heterogeneity, the authors found insufficient convincing evidence to suggest that the MD decreased BP. Further standardized research is urgently needed to reach evidence-based conclusions to clarify the role of MD in BP management, particularly in Europe and other societies where prevalence of cardiovascular diseases is increasing.