Mediterranean diet for the primary prevention of cardiometabolic diseases: evidence from a systematic review and meta-analysis featured in the Italian National Guidelines “La Dieta Mediterranea”

Objectives The Mediterranean diet (MD) is widely recognized for its potential health benefits, yet the extent and certainty of its association with metabolic outcomes remains incompletely understood. The aim of this systematic review and meta-analysis was to evaluate the relationship between adherence to the MD and the risk or prevalence of cardiometabolic disorders in the general population, with a focus on its role in primordial and primary prevention. Methods This review followed PRISMA 2020 and MOOSE guidelines. A systematic search of PubMed/MEDLINE, Scopus, Embase, and the Cochrane Library was conducted through February 28, 2024. Eligible studies examined adherence to the MD in relation to the risk or prevalence of metabolic disorders. Study quality was assessed using the Newcastle–Ottawa Scale, and evidence certainty was rated with the NUTRI-GRADE framework. Pooled effect estimates were calculated using a random-effects model and reported as risk ratios (RR), hazard ratios (HR), or odds ratios (OR), as appropriate. Results Sixty studies comprising over 1.1 million participants were included. Higher MD adherence was consistently associated with a reduced risk of T2DM (RR: 0.96; 95% CI: 0.95–0.97), supported by moderate to high certainty of evidence. Similar inverse associations were observed for overweight (OR: 0.94; 95% CI: 0.91–0.97) and adult obesity (OR: 0.95; 95% CI: 0.93–0.97). The PREDIMED randomized trial further demonstrated a 20% reduction in diabetes incidence with MD intervention. Evidence for metabolic syndrome (RR: 0.98; 95% CI: 0.98–0.99) and hyperuricemia (OR: 0.43; 95% CI: 0.25–0.75) was suggestive of protective effects, though with lower certainty. Associations with hypercholesterolemia and hypertriglyceridemia were inconsistent and inconclusive. Conclusions Adherence to the Mediterranean diet is associated with a lower risk of several metabolic disorders, particularly T2DM and obesity in adults. These findings support the inclusion of the MD in public health strategies for metabolic disease prevention. Further high-quality longitudinal and interventional studies are warranted to clarify its effects on other metabolic outcomes.