Dietary Meat Intake in Relation to Colorectal Adenoma in Asymptomatic Women

OBJECTIVES: No previous study has concurrently assessed the associations between meat intake, meat-cooking methods and doneness levels, meat mutagens (heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons), heme iron, and nitrite from meat and colorectal adenoma in asymptomatic women undergoing colonoscopy. METHODS: Of the 807 eligible women in a cross-sectional multicenter colonoscopy screening study, 158 prevalent colorectal adenoma cases and 649 controls satisfactorily completed the validated food frequency and meat questionnaires. Using an established meat mutagen database and new heme iron and nitrite databases, we comprehensively investigated the components of meat that may be involved in carcinogenesis. Using logistic regression, we estimated odds ratios (ORs) and 95% confidence intervals (CIs) within quartiles of meat-related variables. RESULTS: Red meat was associated positively with colorectal adenoma (OR fourth vs. first quartile = 2.02; 95% CI = 1.06-3.83; P trend = 0.38). Intake of pan-fried meat (OR = 1.72; 95% CI = 0.96-3.07; P trend = 0.01) and the HCA: 2-amino-3,8-dimethylimidazo[4,5-f] quinoxaline (MeIQx) (OR = 1.90; 95% CI = 1.05-3.42; P trend = 0.07) were also associated with an increased risk of colorectal adenoma. The new databases yielded lower estimates of heme iron and nitrite than previous assessment methods, although the two methods were highly correlated for both exposures. Although not statistically significant, there were positive associations between iron and heme iron from meat and colorectal adenoma. CONCLUSIONS: In asymptomatic women undergoing colonoscopy, colorectal adenomas were associated with high intake of red meat, pan-fried meat, and the HCA MeIQx. Other meat-related exposures require further investigation.