Consumption of fast foods and ultra-processed foods and breast cancer risk: a systematic review and meta-analysis

Background The increasing consumption of fast foods (FFs) and ultra-processed foods (UPFs) worldwide has raised concerns due to their association with carcinogenic compounds and potential links to various cancers. However, this evidence about breast cancer risk remains inconsistent. This study aimed to meta-analyze the association between FFs and UPFs consumption and the risk of breast cancer in females. Methods A comprehensive search on online databases was conducted from inception to May 2025, and relevant study data were extracted. The meta-analysis utilized odds ratio (OR) with 95% confidence interval (CI) as effect size measures. Subgroup analyses, heterogeneity assessment, publication bias, and sensitivity analyses were performed to ensure robustness. All statistical analyses were conducted using STATA. Results The pooled analysis of 17 observational studies showed a significant association between the highest FFs and UPFs consumption and increased breast cancer risk (OR 1.25, 95% CI [1.09-1.43], p = 0.001). Subgroup analysis revealed a significant positive association between FFs and UPFs consumption and breast cancer risk in case-control studies, but not in cohort studies or menopausal status and a significant association was observed in studies with sample sizes > 1000 and < 1000. Furthermore, the association was significant in Latin America when BMI adjustment was considered for 'yes' and 'no'. Conclusions This meta-analysis identified a significant association between the consumption of FFs and UPFs and an increased risk of breast cancer, with high intake linked to a 25% greater risk. These findings suggest that diets high in UPFs may play a role in breast cancer development. As UPF consumption continues to rise, public health strategies and regulatory policies targeting food processing, marketing, labeling, and accessibility are essential for cancer risk reduction and prevention.