Greatest effects among postmenopausal women
Closely following the Mediterranean Diet (MeDi), which emphasizes fruits, vegetables, whole grains, legumes, limited lean protein, and healthy fats such as olive oil and nuts, has been linked to a reduced risk of chronic diseases, including several forms of cancer. Numerous studies have shown associations between lower breast cancer risk in women and MeDi adherence. To clarify whether the the MeDi exerts a significant effect on breast cancer risk, researchers conducted a systematic review and meta- analysis that compiled and analyzed the existing evidence across a large international group of studies.
Methods: After a comprehensive literature search, 31 high-quality observational studies were selected for the final analysis (12 cohort studies and 19 case-control studies). Studies were published between 2006 and 2023 and conducted in the Americas, Europe, and Asia, with the majority in the United States and Spain. A total of 1,347,446 women were evaluated, grouped as overall, postmenopausal, and premenopausal. Participants’ ages ranged from 20 to 104 years. Follow-up duration varied between 8 and 33 years in cohort studies.
- A cohort study is an observational study with an active group and control group, allowing researchers to calculate the occurrence of a disease in a population over time.
- A case-control study identifies individuals with a specific disease or condition and assigns “matched controls”—people with the same demographic characteristics who are not part of the study—which enables researchers to evaluate the differences between these groups.
Results: The overall pooled analysis found a clinically significant 13% reduction in breast cancer risk in participants who adhered to the MeDi. The effect was greater in postmenopausal women across all studies and in participants of studies conducted in Asia. A subgroup analysis showed that moderate alcohol use (red wine) did not affect breast cancer risk in the overall group, but an additional reduction in breast cancer risk was seen in postmenopausal women.
Discussion: These results indicate that adherence to the MeDi may help prevent breast cancer, especially in postmenopausal women. It has been suggested that the polyphenols in olive oil and moderate amounts of red wine may contribute to the cancer-protective effects of the MeDi. In addition, phytoestrogens from vegetables and fruits may interact with the body’s estrogen production, thus helping to prevent certain types of breast cancer from developing. The sites of hormone production during the postmenopausal period (fat tissue rather than ovaries) may also account for the increased effect of the MeDi in preventing breast cancer in that population.
Conclusion: Adherence to the MeDi significantly reduced women’s breast cancer risk in a large meta-analysis of international observational studies involving more than a million participants. Future research will help identify the specific anti-cancer mechanisms of the MeDi and illuminate its varying effects across life stages and geographic regions.
Reference: Karimi M, Asbaghi O, Hooshmand F, et al. Adherence to Mediterranean Diet and Breast Cancer Risk: A Meta-Analysis of Prospective Observational Studies. Health Sci Rep. 2025;8(4):e70736.