Effects of dietary interventions on cardiovascular outcomes: a network meta-analysis

Context: Next to a large body of epidemiological observational studies showing that the Mediterranean diet (MD) is an important lifestyle determinant of cardiovascular risk, there is less relevant evidence from well-conducted randomized controlled trials (RCTs) with hard cardiovascular outcomes.Objective: The objective of the study was to identify the most effective dietary intervention for reducing cardiovascular morbidity and mortality.Data Sources: A systematic approach following PRISMA network meta-analyses reporting guidelines was applied to a search of electronic databases (MEDLINE, Cochrane Central Register of Controlled Trials, and Embase) without language restrictions, supplemented by scanning through bibliographies of studies and meetings' abstract material. Inclusion criteria were RCTs conducted in an adult population, investigating the effects of different type of diets or dietary patterns on all-cause mortality and cardiovascular outcomes of interest.Data Extraction: Data extraction for each study was conducted by 2 independent reviewers.Data Analysis: A frequentist network meta-analysis using a random-effects model was conducted. Death from any cardiovascular cause was defined as the primary outcome. A total of 17 trials incorporating 83 280 participants were included in the systematic review. Twelve articles (n = 80 550 participants) contributed to the network meta-analysis for the primary outcome. When compared with the control diet, only the MD showed a reduction in cardiovascular deaths (risk ratio = 0.59; 95% confidence interval, 0.42-0.82). Additionally, MD was the sole dietary strategy that decreased the risk of major cardiovascular events, myocardial infarction, angina, and all-cause mortality.Conclusions: MD may play a protective role against cardiovascular disease and death for primary and also secondary prevention.