Adherence to Mediterranean Diet and Risk of Type 2 Diabetes: An Updated Systematic Review and Dose-Response Meta-analysis.

BACKGROUND: Given the global rise in type 2 diabetes mellitus (T2D), the Mediterranean diet (MedDiet) has gained attention as a promising preventive dietary pattern. OBJECTIVES: This study aims to update and extend our previous systematic review by synthesizing current evidence from randomized controlled trials (RCTs) and prospective cohort studies on the association between MedDiet adherence and incident T2D in adults, and to evaluate the certainty of evidence. METHODS: We conducted a systematic search in MEDLINE, Cochrane CENTRAL, and Scopus from 2014 to May 2025. Eligible studies were prospective cohorts reporting on the adherence to an a priori-defined MedDiet or, for RCTs, MedDiet intervention compared with any other diet and T2D incidence. Random-effects dose-response meta-analyses were performed to estimate hazard ratios (HRs) for MedDiet adherence score. Risk of bias was assessed using the Cochrane risk of bias tool 2 and the Risk Of Bias In Nonrandomized Studies-of Exposures tool, and the certainty of evidence was rated using the Grading of Recommendations Assessment, Development and Evaluation approach. RESULTS: A total of 24 prospective cohort studies and 1 RCT were included, comprising 991,878 participants and 68,325 T2D cases and a mean follow-up duration of 12.2 y (range: 3.5- 25 y). Higher MedDiet adherence is likely associated with a reduced risk of T2D [HRper 2-point increment: 0.92; 95% confidence interval (CI): 0.90, 0.94; moderate certainty]. The dose-response curve shows a consistent decline in T2D risk with higher adherence to MedDiet. The association remained robust over several subgroup analyses, including age, sex, and MedDiet score. The included RCT confirmed the main findings (HR: 0.75; 95% CI: 0.56, 1.01, low certainty). CONCLUSION: This updated systematic review and meta-analysis provides moderate-certainty evidence that greater adherence to the MedDiet is associated with a lower risk of T2D. These findings reinforce current dietary guidelines recommending MedDiet as a sound strategy for T2D prevention.