Association between dietary patterns and the risk of breast cancer in South Asian countries: a protocol for a systematic review and meta-analysis of observational studies

Introduction To date, breast cancer is the fourth leading cause of mortality globally, while Asian women have the highest mortality reporting ∼47.3%. Epidemiological evidence suggests that the association of dietary pattern is closely linked to the risk of breast cancer. A comprehensive analysis of underlying mechanisms could help to identify modifiable risk factors, ultimately reducing a significant disease burden. The review protocol aims to explore the critical association across subtypes and narratively synthesise the possible mechanism between dietary patterns and breast cancer development among South Asian adult women (≥18 years). Methods and analysis The research team will search the MEDLINE (PubMed), Scopus, Web of Sciences, Embase and Google Scholar databases from inception to 30 November 2025 using truncated and phrase-searched keywords and relevant subject headings. Observational studies published in English language, and reporting the association between dietary patterns, cancer subtypes and breast cancer risk among adult women in South Asia using validated assessment tools, will be included. Two reviewers will screen the retrieved papers independently, while any disagreements between them will be resolved by a third reviewer. Demographics, breast cancer type and dietary patterns, along with their associations, will be extracted for meta-analysis and the findings will be summarised furthermore. Forest plots will be constructed in R (V.4.3.2), with heterogeneity assessed using I ² statistic, complemented by publication bias assessment (funnel plot) and sensitivity analysis. The included studies will be critically assessed using the Joanna Briggs Institute’s critical appraisal tools. A quantitative synthesis will also be conducted if the included studies are sufficiently homogeneous using a random-effects model and risk factors will be narratively synthesised. In addition, meta-analysis will be completed by subgroups and sensitivity analysis. Ethics and dissemination The review will synthesise evidence extracted from published studies. As the review will not involve the collection of primary data, ethical approval will not be required. Findings will be disseminated through a peer-reviewed publication. PROSPERO registration number CRD42025644702.