Abstract
The relationships among meat consumption, smoking habits, and phenotypic cytochrome P450 2A6 variation with respect to colorectal cancer risk remain unclear. In this study, the relationships among colorectal tumour risk, meat consumption by questionnaire, and phenotypic P450 2A6 activity by genotyping in a case-control study (299 cases and 170 controls) were analyzed for never-smokers and ever-smokers. In never-smokers consuming ≥1 serving per day of total meat, a significant odds ratio of 4.42 (95% confidence interval, 1.29 - 15.2), adjusted by logistic regression for age and gender, was observed, compared with the group consuming ≤2 servings per week. Furthermore, in Japanese never-smokers, the susceptibility to colorectal tumours was dependent on the frequency of meat intake (trend test p = 0.011). In never-smokers who were P450 2A6 poor metabolizers and had a high frequency of meat intake, the apparent odds ratio was 3.57 (95% confidence interval, 0.30 - 42.2) compared with the P450 2A6 normal group with a low meat intake frequency. These results suggested that colorectal tumour risk was inversely associated with the phenotypic P450 2A6 activities in Japanese never-smokers with a high meat intake.
Highlights
The consumptions of red meat, processed meat, and high-fat products and smoking have been positively associated with colorectal tumour risk in previous epidemical studies [1] [2] [3] [4] [5]
In never-smokers who were P450 2A6 poor metabolizers and had a high frequency of meat intake, the apparent odds ratio was 3.57 (95% confidence interval, 0.30 - 42.2) compared with the P450 2A6 normal group with a low meat intake frequency. These results suggested that colorectal tumour risk was inversely associated with the phenotypic P450 2A6 activities in Japanese never-smokers with a high meat intake
Because the highest risk of colorectal tumours was previously found in subjects with both high P450 2A6 activity and high cumulative tobacco exposure [8], separate analyses were performed for never-smokers and ever-smokers (Figure 1)
Summary
The consumptions of red meat, processed meat, and high-fat products and smoking have been positively associated with colorectal tumour risk in previous epidemical studies [1] [2] [3] [4] [5]. We previously found that a high risk of colorectal tumours in Japanese subjects was associated with higher P450 2A6 activity and higher cumulative tobacco exposure [8]. Compared with the abundant data from Western countries [1] [2] [3] [4], evidence regarding meat consumption and colorectal cancer is limited in the Japanese population. The relationships among meat consumption, smoking habits, and phenotypic P450 2A6 variation with respect to colorectal cancer risk remain unclear
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