Adherence to Mediterranean Diet and Breast Cancer Risk: A Meta-Analysis of Prospective Observational Studies

The Mediterranean diet (MD) is widely recognized for its health benefits and potential protective effects against various chronic diseases such as cardiovascular conditions and cancer. This meta-analysis evaluates the association between MD adherence and breast cancer risk in women.

A comprehensive search of major databases was conducted until November 2024 to identify cohort or case-control studies. The meta-analysis employed a random-effects model to pool multivariable-adjusted effect sizes, reporting them as hazard ratios (HR) while evaluating heterogeneity using the I² statistic and assessing publication bias.

The pooled analysis of 31 studies indicated a significant association between adherence to the MD and a 13% risk reduction in risk of breast cancer (HR: 0.87, 95% CI: 0.82-0.92; I ² = 70%). Specifically, postmenopausal women exhibited a 12% significant reduction in the risk of breast cancer (HR: 0.88; 95% CI: 0.84, 0.92), while premenopausal women showed no significant effect (HR: 0.98, 95% CI: 0.90, 1.06). Geographically, the effect was most pronounced in Asia (OR: 0.59, 95% CI: 0.50, 0.68), while from America (OR: 0.92, 95% CI: 0.82, 1.02) and Europe (OR: 0.90, 95% CI: 0.83, 0.97) showed moderate associations. Subgroup analysis suggested a stronger significant association in case-control studies (HR: 0.77, 95% CI: 0.70, 0.85), whereas no significant association was observed in cohort studies (HR: 0.96, 95% CI: 0.90, 1.02).

Adherence to the Mediterranean diet is associated with a significant reduction in breast cancer risk, particularly among postmenopausal women and in regions such as Asia. These findings suggest that the Mediterranean diet may be an important dietary factor in reducing breast cancer risk, especially in certain populations. However, further research is needed to confirm its impact in different study designs and geographical areas.