Monday Nov 24 2008 (foodconsumer.org) -- Eating red meat and processed meat may increase risk of cancer in the small intestine, according to an observational study published in the current issue of the journal Cancer Research.

During the 8-year study of nearly half a million men and women, Amanda Cross, Ph.D., a National Cancer Institute researcher and the study's lead author, found 60 cases of adenocarcinomas and 80 cases carcinoid tumors of the small intestine were recorded.

There was no clear connection between red and processed meat and these tumors, but Cross and colleagues suggested a noticeably elevated risk for carcinoid tumors in the small intestine in association with saturated fat intake

Evidence also suggests that cancers of the small and large bowel both arise from adenomatous polyp precursor lesions and the large intestine is more susceptible to carcinogenesis.

Cancer of the small intestine is rare, but the incidence has been increasing since 1970s.    People who develop this cancer are more likely than others to also develop a second primary cancer such as colorectal cancer, according to Cross and colleagues.

Another study published in the Nov 2008 issue of Cancer epidemiology, biomarkers & prevention suggested that eating lots of meat may increase colorectal cancer regardless of genotypes of certain genes involved in the metabolism of carcinogens formed in overcooked meat.

The case-control study led by Cotterchio M and colleagues from Cancer Care Ontario in Toronto, Canada found those who ate more than 5 servings of meat per week were 67 percent more likely to develop colorectal cancer than those who ate 2 or less than 2 servings per week.

For the study, the researchers surveyed 1,095 patients age 20 to 74 who were diagnosed with colorectal cancer between 1997 and 2000 and 1,890 age- matched control using epidemiologic and food questionnaires.

Blood samples from 842 cases and 1,252 controls were also analyzed for genetic variants in 15 enzymes involved in the metabolism of cancer-causing agents formed in overcooked meat including cytochrome P450, glutathione S-transferase, UDP-glucuronosyltransferases, SULT, NAT, mEH, and AHR.

The researchers found red meat consumption was associated with a 67 percent increased risk of colorectal cancer while the cancer risk in those who ate more than 2 servings per week was increased by 57 percent compared to those who ate 2 or less than 2 servings per week.

They said CYP2C9 and NAT2 variants were associated with colorectal cancer risk.  And they found red meat intake was associated with elevated colorectal cancer risk regardless of the statuses of their genotypes.  

However, they also found that persons with CYP1B! and SULT1A! Variants were at the highest risk of the cancer. And well-done red meat intake was associated with an elevated risk of colorectal cancer regardless of carcinogen-metabolizing genotype.