The effectiveness of the Mediterranean Diet for primary and secondary prevention of cardiovascular disease: An umbrella review.

AIMS

This study aimed to review meta-analyses of randomised controlled trials that evaluated the effectiveness of the Mediterranean Diet for the primary and secondary prevention of cardiovascular disease.

METHODS

Five databases (Medline, Embase, Cochrane, CINAHL and ProQuest) were searched from inception to November 2022. Inclusion criteria were: (i) systematic review of randomised controlled studies with metanalysis; (ii) adults ≥18 years from the general population with (secondary prevention) and without (primary prevention) established cardiovascular disease; (iii) Mediterranean Diet compared with another dietary intervention or usual care. Review selection and quality assessment using AMSTAR-2 were completed in duplicate. GRADE was extracted from each review, and results were synthesised narratively.

RESULTS

Eighteen meta-analyses of 238 randomised controlled trials were included, with an 8% overlap of primary studies. Compared to usual care, the Mediterranean Diet was associated with reduced cardiovascular disease mortality (n = 4 reviews, GRADE low certainty; risk ratio range: 0.35 [95% confidence interval: 0.15-0.82] to 0.90 [95% confidence interval: 0.72-1.11]). Non-fatal myocardial infarctions were reduced (n = 4 reviews, risk ratio range: 0.47 [95% confidence interval: 0.28-0.79] to 0.60 [95% confidence interval: 0.44-0.82]) when compared with another active intervention. The methodological quality of most reviews (n = 16/18; 84%) was low or critically low and strength of evidence was generally weak.

CONCLUSIONS

This review showed that the Mediterranean Diet can reduce fatal cardiovascular disease outcome risk by 10%-67% and non-fatal cardiovascular disease outcome risk by 21%-70%. This preventive effect was more significant in studies that included populations with established cardiovascular disease. Better quality reviews are needed.