Frequent red and processed meat consumption leaves a specific pattern of DNA damage in colorectal cells that contributes to the formation of tumors, researchers reported in study findings published in Cancer Discovery.

Diets high in red and processed meats have long been identified as carcinogenic, but until now researchers have not understood the mechanisms of why. For the current study, the researchers conducted whole-exome sequencing on healthy and tumor tissue samples from 900 patients with colorectal cancer who were part of the Nurses’ Health Studies I and II and the Health Professionals Follow-Up Study.

The researchers identified several mutational signatures in the tumor tissue, including an alkylating signature that was associated with red meat consumption. They found that those with the highest red meat consumption (i.e., > 150 g [two servings] per day) had the highest levels of an alkylating DNA damage signature. The signature was not linked to diets high in chicken or fish or other lifestyle risk factors for cancer (e.g., smoking, high body mass index, high alcohol consumption).

Additionally, more cells in the distal colon had the alkylating signature, where most colorectal cancers tend to develop, and tumors with the highest levels of the signature were associated with worse outcomes. The researchers also found that tumors with the signature were more likely to have KRAS and PIK3CA genetic variants.

“These results link for the first time a colorectal mutational signature to a component of diet, and further implicate the role of red meat in colorectal cancer initiation and progression,” the researchers concluded.