Background: Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death among females. The goal of this scoping review is to map and evaluate available evidence on how research is conducted regarding the state of the art of the effect of omega-3 consumption on breast cancer incidence in premenopausal and postmenopausal women and across ethnicities. This will provide guidance that could be used to inform a future systematic review.  

Objective: This scoping review aims to identify and map available evidence investigating the effect of omega-3 consumption on breast cancer incidence among premenopausal and postmenopausal women.

Methods: Using the PRISMA-ScR approach, we conducted a comprehensive search in Embase, MEDLINE, Clinicaltrials.gov, and medRxiv without date restriction through November 2025. Screening was conducted according to a pre-defined set of criteria, and a final sample of 78 articles was identified.

Results: The results revealed variation in the reporting of Omega-3 fatty acid types, data collection methods, and gaps in study design, menopausal status definitions, and ethnicity inclusion across studies. Most studies were case-control studies (n= 39), prospective cohort studies (n = 24), and nested case-control studies (n = 10), with odds ratios being the most commonly reported effect measure. Studies assessed both premenopausal and postmenopausal women (n=48), postmenopausal women (n=23), and premenopausal women (n=7), with reporting of ethnicity inclusion (n=33). Food frequency questionnaires and biological samples were the most frequently used data collection methods to assess dietary intake measures, n-3 biomarkers, and n-3 supplementation.

Conclusion and future implications: This scoping review provides a comprehensive synthesis of the literature examining omega-3 fatty acids and breast cancer incidence among premenopausal and postmenopausal women, as well as identifies and maps key methodological processes and gaps in the existing evidence. Overall, the literature reveals substantial heterogeneity in study design, omega-3 exposure assessment, definitions of menopausal status, and assessment of effect measures. The evidence from 78 primary studies included in this scoping review suggests the need for addressing identified methodological gaps in future research on this topic, and that the insights gained will help further develop this field of investigation. The findings of this review are hoped to provide a foundation to inform and conduct a future systematic review. 

Omega-3 Fatty Acids Intake and Breast Cancer Incidence among Premenopausal and Postmenopausal Women: A Scoping Review