Researchers find biological links between red meat and colorectal cancer
- Detective work -The strength of this approach is that the people documenting their diet had no way of knowing of their future cancer diagnosis, rather than asking people to recall their eating habits after they became ill. The analysis revealed a distinct mutational signature -- a pattern that had never before been identified but was indicative of a type of DNA damage called "alkylation." Not all cells that contain these mutations will necessarily become cancerous, and the signature was present in some healthy colon samples too. The mutation signature was significantly associated with intake of red meat, both processed and unprocessed, prior to the patient's diagnosis of cancer, but not with the intake of poultry, fish or other lifetsyle factors that were examined. "With red meat, there are chemicals that can cause alkylation," explained Giannakis. The specific compounds are nitroso compounds that can be made from heme, which is plentiful in red meat, as well as nitrates, often found in processed meat.
- Moderation urged -In this case, the suspicious mutation signature has a lot to answer for: patients whose tumors had the highest levels of alkylation damage had a 47 percent greater risk of colorectal cancer-specific death, compared to patients with lower levels of damage. But Giannakis, also a practicing doctor, said it was important to focus on how the research can be used to help patients. Future work might help physicians identify which patients are genetically predisposed to accumulating alkylation damage, then counsel them to limit their red meat intake. Identifying patients who have already started to accrue the mutational signature could help identify who's at greater risk of developing cancer, or catch the disease at an earlier stage. And because the amount of alkylation damage appears to be a biomarker of patient survival, it could possibly be used to tell patients about their prognosis. Finally, understanding the biological pathway through which colorectal cancer occurs paves the way for medicines that interrupt or reverse the process, preventing the disease. Giannakis stressed the takeaway message is not that people should totally abstain from red meat: "My recommendation would be that moderation and a balanced diet is key." High levels of tumor alkylation damage were only seen among patients eating on average more than 150 grams (five ounces) a day, roughly equal to two or more servings.
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