Professor Arizona State University Phoenix, Arizona, United States
Objectives: Because bread contains potential carcinogens, and is widely consumed, the purpose of this investigation was to determine whether bread consumption is associated with increased cancer risk, based on data from prospective cohort studies. In view of the broader findings on total grain intake and cancer risk, it was hypothesized that bread consumption would not be associated with increased cancer risk.
Methods: To assess the association between bread consumption and cancer risk, Pubmed and Scopus databases were searched for relevant prospective cohort studies that provided risk ratios for bread consumption and cancer incidence or mortality. Meta-analysis was performed according to the Meta-analysis of Observational Studies in Epidemiology (MOOSE) reporting guideline using Cochrane’s RevMan 5.4.1 software, applying inverse variance risk ratios in random effects models. Heterogeneity was assessed with Cochrane’s Q (Chi2) and I2 statistics.
Results: Eighteen studies were identified that met inclusion criteria. Overall, bread consumption was not associated with higher cancer risk, with >93% of 75 reported risk ratios indicating either no association or a significantly lower risk associated with the highest intake group. In most studies, bread was defined as either whole grain or wholemeal. In a categorical meta-analysis (highest vs. lowest intakes), the group with the highest intake of bread (whole grain, wholemeal, non-white) had an 11% lower risk of cancer mortality (hazard ratio (HR) = 0.89; 95% confidence interval (CI), 0.81-0.97; Chi2=4.3; I2=7%; 5 studies). Highest intake of bread (total, whole grain, wholemeal) was also associated with a 10% lower risk of colorectal cancer incidence (HR = 0.90; 95% CI, 0.81-1.00; Chi2=5; I2=0%; 7 studies). High intake of bread was not associated with breast cancer risk (HR = 1.06; 95% CI, 0.82-1.38; Chi2=12.6; I2=60%; 6 studies). Insufficient numbers of studies were available to determine risk for other site-specific cancers.
Conclusions: The results of this meta-analysis indicate that bread consumption is not associated with increased cancer risk. Indeed, meta-analyses revealed that bread consumption is associated with lower risk of total cancer mortality and colorectal cancer incidence.
