Abstract
CONTEXT: Several prospective cohort studies have investigated the association between glycemic index (GI), glycemic load (GL), dietary sugar, and total dietary fiber intake, with female breast cancer (BC) risk and reported inconsistent results. In the last decade, several large epidemiological studies have investigated these associations, suggesting the need to revisit the current body of evidence. OBJECTIVE: The aim of this study was to update a systematic review and meta-analysis conducted by Schlesinger et al in 2017 using recent scientific evidence published since 2015. DATA SOURCES: Publications indexed in PubMed, Embase, and The Cochrane Library were retrieved from the inception of the database up to January 2024. DATA EXTRACTION: Two reviewers independently extracted data and assessed each study's quality. DATA ANALYSIS: A random-effects model was used to estimate summary risk ratios (RRs) and 95% CIs for a meta-analysis that included 33 publications, with 26 prospective cohort studies cumulatively enrolling 2 212 645 women, among whom 79 777 were diagnosed with incident BC. RESULTS: Dietary GI and GL (highest vs lowest exposure intake) were both associated with 5% higher BC risk-RR (95% CI): 1.05 (1.01-1.09; P = .007) and 1.05 (0.97-1.13; P = .24), respectively. No clear associations were observed for sugar and total dietary fiber intake (highest vs lowest exposure intake)-RR (95% CI): 1.12 (0.95-1.11; P = .16) and 0.93 (0.86-1.00; P = .05), respectively. For the latter, the association was more pronounced among premenopausal women (RR: 0.78; 95% CI: 0.68-0.90; P = .0008). CONCLUSION: This meta-analysis supports a significant positive association between high dietary GI intake and higher risk of BC and a significant inverse association between high dietary fiber intake and lower risk of BC. Interventions promoting a high-fiber and low-sugar diet may be useful components of BC-prevention strategies. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration no. CRD42023463143.