A sweeping global review shows that the Mediterranean diet significantly reduces breast cancer risk in postmenopausal women, with Asian populations seeing the strongest effects, highlighting the diet’s potential as a strategic prevention tool. Review: Adherence to Mediterranean Diet and Breast Cancer Risk: A Meta-Analysis of Prospective Observational Studies. Image Credit: Sea Wave / Shutterstock In a recent study published in the journal Health Science Reports, researchers evaluated the associations between adherence to the Mediterranean diet (MD) and breast cancer risk. Breast cancer is a significant public health concern, accounting for a substantial proportion of cancer diagnoses among women. As such, exploring effective prevention strategies remains crucial, focusing on lifestyle factors, such as diet. The MD has drawn substantial research interest due to its associations with health benefits. Moreover, studies suggest an inverse relationship between adherence to the MD and breast cancer risk, albeit some inconsistencies remain. The mechanisms underlying this relationship may include the anti-inflammatory and antioxidant properties of the diet, as well as hormonal factors, particularly in postmenopausal women. About the study In the present study, researchers examined the evidence on the relationship between the MD and breast cancer risk. First, PubMed, Scopus, and Web of Science databases were searched for case-control and cohort studies examining adherence to the MD and its association with breast cancer risk. They also reported risk estimates using odds, relative, or hazard ratios. Studies that lacked quantitative data, non-original studies (e.g., reviews), and those involving other dietary patterns were excluded. Next, relevant data from studies were extracted; these included sample size, participant characteristics (age, menopausal status), dietary assessment methods and duration, alcohol intake, and risk estimates. The quality of the included studies was assessed using the Newcastle-Ottawa Scale (NOS). Further, the meta-analysis was performed by pooling risk estimates comparing the lowest and highest levels of MD adherence. Heterogeneity was assessed using the I-squared statistic, and publication bias was examined using Funnel plots and Begg’s test. In addition, the team performed subgroup analyses by study design, regions, and menopausal status to analyze whether these variables modified risk estimates. The researchers also conducted sensitivity analyses to assess the robustness of their findings and examined the impact of adjusting for alcohol consumption, an element of the Mediterranean diet whose role in breast cancer risk is debated. Findings The comprehensive database search yielded 2,189 records. Following deduplication and title/abstract screening, full texts of 43 studies were reviewed, resulting in the inclusion of 31 studies. These included 19 case-control and 12 cohort studies published between 2006 and 2023. Participants were aged 20–104 years across studies. The quality of included studies was generally high, with case-control and cohort studies scoring 3–9 and 6–9 on the NOS, respectively. The meta-analysis indicated a significant association between MD adherence and lower breast cancer risk overall, with substantial heterogeneity across studies. However, for premenopausal women, there was no significant risk reduction, with some heterogeneity across studies. By contrast, for postmenopausal women, there was a significant decrease in breast cancer risk associated with adherence to the MD, with moderate heterogeneity. Further, cohort studies with less than and over 20 years of follow-up showed no significant differences in breast cancer risk. By geographical region, studies performed in Asia showed the strongest associations between MD adherence and breast cancer risk. European studies showed moderate associations, while American studies had insignificant associations. For premenopausal women in cohort studies, the MD had no effect on breast cancer risk; likewise, the marginal association in case-control studies appeared overestimated. By region, premenopausal women had no significant risk reduction across Asia, the Americas, or Europe. For postmenopausal women in cohort studies, there was a modest decrease in breast cancer risk associated with MD adherence, while a stronger protective effect was noted in case-control studies. Moreover, there was a moderate risk reduction in Europeans, a weaker, insignificant reduction in Americans, and a stronger association in Asians. The analysis also found that including or excluding alcohol as a component of the Mediterranean diet influenced the magnitude of risk reduction in some subgroups, especially among postmenopausal women, highlighting the complex and still-debated role of alcohol in breast cancer prevention. A leave-one-out sensitivity analysis found no outlier studies, supporting the robustness of the findings. Limitations Limitations of the study include differences in findings between cohort and case-control studies, with case-control studies generally showing a stronger association but also having a higher risk of recall bias and other methodological challenges. Additionally, variations in how the Mediterranean diet is defined and implemented across different regions—often due to cultural factors—may have contributed to inconsistent results. The authors note that further research should consider breast cancer subtypes, hormone receptor status, genetic predispositions, and lifestyle factors to more fully understand the potential protective role of the Mediterranean diet. Conclusions In sum, the findings of the meta-analysis indicate a 13% lower risk of breast cancer associated with adherence to the MD, especially in postmenopausal women. There were no significant effects for premenopausal women. Geographically, Asian populations had the strongest protective effects, with moderate associations in Europeans and Americans. While these results suggest that the MD may be a promising diet to prevent breast cancer, the authors emphasize the need for additional, well-designed studies across diverse populations and regions, and taking into account the complexity of diet composition and other risk factors.