Bread Consumption and Cancer Risk: Systematic Review and Meta-Analysis of Prospective Cohort Studies

Because bread can contain potential carcinogens such as acrylamide, and is widely consumed, we conducted a systematic review and meta-analysis to determine whether bread consumption is associated with increased cancer risk. PubMed and Medline databases were searched up to 1 March 2024, for studies that provided hazard ratios (HRs) (or similar) for bread consumption and cancer incidence or mortality. Only prospective cohort studies were included. We used the Preferred Reporting Items of Systematic reviews and Meta-Analyses checklist. Meta-analysis was performed with Cochrane's RevMan 5.4.1 software using a DerSimonian-Laird random-effects model. Heterogeneity was assessed with Cochrane's Q (χ²) and I ² statistics, and publication bias was assessed with Egger's test. Twenty-four publications met inclusion criteria, including 1,887,074 adults, and were included in the systematic review. Ten publications that provided HRs were included in the meta-analysis for highest compared with lowest intakes, and an additional 7 publications that provided mortality or incident rate ratios or relative risks were included in supplemental meta-analyses. Of 108 reported HRs (or similar), 97 (79%) were either not statistically significant (n = 86) or indicated lower cancer risk (n = 11) associated with the highest intakes of bread. The meta-analysis indicated that bread intake was not associated with site-specific cancer risk [HR: 1.01; 95% confidence interval (CI): 0.89, 1.14; P = 0.92; 8 publications] or total cancer mortality (HR: 0.90; 95% CI: 0.73, 1.11; P = 0.32; 2 publications). Supplemental meta-analyses using all risk estimates in addition to HRs confirmed these findings. Whole-grain bread was associated with a lower site-specific cancer risk, mainly because of reduced colorectal cancer risk. Results of the systematic review and meta-analysis indicate that bread consumption is not associated with increased site-specific cancer risk, whereas high whole-grain/nonwhite bread consumption is associated with lower total cancer mortality and colorectal cancer risk. This study was registered at Clinical Trials Registry of PROSPERO as registration number CRD42023414156.