Urinary 1-methylhistidine and 3-methylhistidine, meat intake, and colorectal adenoma risk.

Self-reported red and processed meat intake has been positively associated with colorectal adenoma and cancer; however, measurement error in self-reported data can attenuate risk estimates, increasing the need for improved exposure assessment methods to better understand this association. A controlled feeding study revealed that urinary 1-methylhistidine and 3-methylhistidine levels were dose-dependently associated with meat intake; our aim was to examine these analytes in relation to colorectal adenoma. Individuals undergoing routine cancer screening by sigmoidoscopy or colonoscopy were recruited for a colorectal adenoma case-control study; participants completed a food frequency questionnaire and a meat questionnaire, and donated urine. Urinary 1-methylhistidine and 3-methylhistidine levels were measured in 131 case-control pairs (age, sex, and smoking matched); odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by logistic regression. Although the mean self-reported red meat intake was higher in cases (59 g/day) than in controls (48 g/day), the mean urinary 1-methylhistidine and 3-methylhistidine levels did not differ by case status (P=0.72). Neither urinary 1-methylhistidine nor urinary 3-methylhistidine was associated with colorectal adenoma (OR continuous=0.90, 95% CI: 0.53-1.54; OR continuous=0.90, 95% CI: 0.69-1.17, respectively). A variable combining self-reported red meat intake with urinary 1-methylhistidine and 3-methylhistidine levels was not associated with colorectal adenoma. Analyzing urine samples from multiple days from 17 individuals revealed intraclass correlations of 0.52 and 0.49 for 1-methylhistidine and 3-methylhistidine, respectively; this variability could result in attenuated risks. Urinary 1-methylhistidine and 3-methylhistidine levels, measured in one sample, were not associated with colorectal adenoma.