CHICAGO — High intake of red meat has been linked to increased risk of colorectal cancer in many studies, and a new study has found a possible reason.
NAT2 genotype appears to activate carcinogenic heterocyclic amines produced in cooked red meat and in cigarette smoke, the investigators reported at the annual Digestive Disease Week.
Using data from nearly 33,000 women enrolled in the prospective Nurses' Health Study, Andrew Chan, M.D., and his coauthors examined the risk of incident colorectal cancer according to NAT2 genotypes, meat intake, and smoking. They matched 183 women with colorectal cancer to 443 controls (Int. J. Cancer 2005;115:648–52). They found that the acetylator genotype alone did not significantly increase cancer risk.
However, women with rapid acetylator genotypes had a markedly increased risk of colorectal cancer if they consumed more than half a serving a day of beef, pork, or lamb, he reported. Their risk was three times that of women who ate less red meat; if they also were longtime smokers, they had a nearly 18-fold increased risk. Among slow acetylators, meat intake did not raise the risk of colorectal cancer.
“We definitely found in a large population that women who consumed less red meat decreased their colorectal cancer risk,” Dr. Chan said.
He cautioned, however, that their sample size of 183 patients was too small. The research does suggest that some women may be more genetically predisposed to the higher risk of colorectal cancer associated with meat and smoking, he said.
They plan future studies to analyze data they collected on cooking methods, to determine whether the method and temperature for cooking meat influence the risk of cancer. The Nurses' Health Study is an ongoing set of investigations studying the risk factors of major chronic diseases in women.
High intake of red meat activates the NAT2 genotype, which increases a patient's risk for colorectal cancer. Vivian E. Lee