A recent study published in Current Developments in Nutrition sheds light on the complex relationship between bread consumption and cancer risk, revealing that whole-grain bread may offer protective benefits against colorectal cancer, while white bread could pose potential risks.
Bread is a staple food consumed globally, known for its nutrient density. However, its processing can lead to the formation of harmful compounds like acrylamide, which the International Agency for Research on Cancer (IARC) classified as “probably carcinogenic to humans” in 1994. Despite this classification, the link between acrylamide and cancer risk remains inconclusive, with many studies producing inconsistent findings. Additionally, many types of bread have a moderate to high glycemic index (GI), which has also been associated with cancer risk, albeit with low and inconsistent estimates.
Colorectal cancer represents the third most common cancer worldwide, accounting for about 10% of all cancer cases and serving as the second leading cause of cancer-related deaths globally. This study aimed to assess whether bread intake is associated with cancer risk by reviewing prospective cohort studies.
Researchers conducted a comprehensive search of the MEDLINE and PubMed databases, focusing on studies that reported incidence or mortality rates specifically linked to bread consumption. A total of 29 studies were evaluated, with 10 included in the meta-analysis. The studies encompassed more than 1.88 million adults, predominantly from Europe, with 63.2% being female.
Bread types varied widely and included classifications such as dark, whole-grain, non-white, and white bread. Most studies focused on colorectal cancer, with some examining breast and prostate cancer.
From the analysis, it was found that the highest quartile of non-white bread intake was associated with a 21% reduction in cancer mortality among males. Furthermore, increasing the consumption of whole-grain or non-white bread by one slice per day correlated with a 4% to 12% decrease in colorectal cancer incidence. Conversely, higher white bread consumption was linked to increased risks of rectal and colon cancers.
Interestingly, in a Japanese cohort, high bread intake did not correlate with colorectal cancer risk. However, the highest tertile of white bread consumption was associated with a 35% increase in rectal cancer incidence and a 22% increase in colon cancer incidence. For breast cancer, while some studies showed a reduction in risk with high-fiber bread, others indicated an increased risk associated with daily rye bread consumption.
No significant associations were found between bread intake and cancers of the endometrium, stomach, lung, or ovary. Additionally, a meta-analysis of studies examining total cancer mortality revealed no links to whole-grain bread consumption. However, supplemental analyses indicated a 10% reduction in total cancer mortality associated with non-white or wholemeal bread.
The study notes that while whole-grain bread may contain higher levels of acrylamide compared to white bread, its antioxidants, fiber, and bioactive compounds likely outweigh potential risks. The researchers acknowledged limitations such as overlapping cohorts and possible publication bias, but emphasized the robustness of their findings due to consistent results across multiple datasets.
Conclusion
Overall, the findings suggest that bread consumption is not associated with increased cancer incidence or mortality, with nearly 90% of outcomes showing no significant links or reductions in risk with higher bread intake. Notably, high consumption of whole-grain bread was linked to a lower risk of colorectal cancer and total cancer mortality, challenging the notion that bread is inherently harmful in the context of cancer risk. This research underscores the importance of considering bread type in dietary choices and its potential implications for cancer prevention.
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