The Mediterranean diet reduces the risk of breast cancer by 13%, postmenopausal women benefit the most

The Mediterranean diet reduces the risk of breast cancer by 13%, postmenopausal women benefit the most

A comprehensive global review shows that the Mediterranean diet significantly reduces breast cancer risk in postmenopausal women, with Asian populations having the greatest impact, highlighting the diet's potential as a strategic prevention tool.

In a study recently published in the journalHealth Science ReportsResearchers evaluated the associations between adherence to the Mediterranean diet (MD) and breast cancer risk.

Breast cancer is a significant public health problem and accounts for a significant proportion of cancer diagnoses in women. Therefore, research into effective prevention strategies remains crucial and focuses on lifestyle factors such as diet. MD has attracted significant research interest due to its associations with health benefits. Furthermore, studies suggest an inverse relationship between MD adherence and breast cancer risk, although some inconsistencies exist. 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 for the relationship between MD and breast cancer risk. First, PubMed, Scopus, and Web of Science databases were searched for case-control and cohort studies examining MD adherence and its association with breast cancer risk. They also reported risk estimates using odds, relative, or at-risk ratios.

Studies missing 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), nutritional assessment methods and duration, alcohol intake, and risk estimates. The quality of included studies was assessed using the Newcastle-Ottawa Scale (NOS).

In addition, the meta-analysis was performed by pooling risk estimates comparing the lowest and highest 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 conducted subgroup analyzes by study design, regions, and menopausal status to analyze whether these variables changed risk estimates. The researchers also conducted sensitivity analyzes to assess the robustness of their results and examine the effects of adjusting alcohol consumption, an element of the Mediterranean diet whose role in breast cancer risk is debated.

Results

The comprehensive database search resulted in 2,189 records. After 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 in studies were between 20 and 104 years old.

The quality of included studies was generally high, with case-control and cohort studies scoring 3–9 and 6–9 on the NOS. Overall, the meta-analysis showed a significant association between MD adherence and lower breast cancer risk, with significant heterogeneity across studies. However, for premenopausal women there was no significant risk reduction, with heterogeneity across studies in all cases.

In contrast, in postmenopausal women, there was a significant decrease in breast cancer risk associated with MD adherence, with moderate heterogeneity. Furthermore, cohort studies with less than and more than 20 years of follow-up showed no significant differences in breast cancer risk. Geographically, studies conducted in Asia demonstrated the strongest associations between MD adherence and breast cancer risk.

European studies showed moderate associations, while American studies had insignificant associations. In premenopausal women in cohort studies, MD had no effect on breast cancer risk. Likewise, border association appeared overestimated in case-control studies. Regionally, premenopausal women in Asia, America or Europe had no significant risk reduction.

Among postmenopausal women in cohort studies, the breast cancer risk associated with MD adherence was modest, whereas a stronger protective effect was found in case-control studies. In addition, 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 extent of risk reduction in some subgroups, particularly in postmenopausal women, highlighting the complex and still debated role of alcohol in breast cancer prevention.

A leave-one-out sensitivity analysis revealed no outlier studies supporting the robustness of the results.

restrictions

Limitations of the study include differences in findings between cohort and case-control studies, with case-control studies generally showing stronger association but also having a higher risk of recall bias and other methodological challenges. Additionally, variations in the definition of the Mediterranean diet in different regions – often due to cultural factors – 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 better understand the potential protective role of the Mediterranean diet.

Conclusions

Overall, the results of the meta-analysis indicate a 13% lower risk of breast cancer associated with adherence to MD, particularly 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 MD may be a promising diet to prevent breast cancer, the authors emphasize the need for additional, well-designed studies in different populations and regions and taking into account the complexity of dietary composition and other risk factors.

Sources: