Meat consumption and the risk of incident distal colon and rectal adenoma

BACKGROUND: Most studies of meat and colorectal adenoma have investigated prevalent events from a single screening, thus limiting our understanding of the role of meat and meat-related exposures in early colorectal carcinogenesis. METHODS: Among participants in the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial who underwent baseline and follow-up sigmoidoscopy (n = 17 072), we identified 1008 individuals with incident distal colorectal adenoma. We calculated odds ratios (ORs) and 95% confidence intervals (95% CIs) for associations between meat and meat-related components and incident distal colorectal adenoma using multivariate logistic regression. RESULTS: We observed suggestive positive associations for red meat, processed meat, haeme iron, and nitrate/nitrite with distal colorectal adenoma. Grilled meat (OR = 1.56, 95% CI = 1.04-2.36), well or very well-done meat (OR = 1.59, 95% CI = 1.05-2.43), 2-amino-1-methyl-6-phenyl-imidazo[4,5-b] pyridine (PhIP) (OR = 1.75, 95% CI = 1.17-2.64), benzo[a] pyrene (OR = 1.53, 95% CI = 1.06-2.20), and total mutagenic activity (OR = 1.57, 95% CI = 1.03-2.40) were positively associated with rectal adenoma. Total iron (diet and supplements) (OR = 0.69, 95% CI = 0.56-0.86) and iron from supplements (OR = 0.65, 95% CI = 0.44-0.97) were inversely associated with any distal colorectal adenoma. CONCLUSION: Our findings indicate that several meat-related components may be most relevant to early neoplasia in the rectum. In contrast, total iron and iron from supplements were inversely associated with any distal colorectal adenoma. British Journal of Cancer (2012) 106, 608-616. doi: 10.1038/bjc.2011.549 www.bjcancer.com Published online 13 December 2011 (C) 2012 Cancer Research UK