Dietary patterns and colorectal cancer risk: the Singapore Chinese Health Study

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BACKGROUND. A greater influence of Western diet and lifestyle factors have been observed among Singapore Chinese and may contribute to the population’s rise in colorectal cancer incidence. Using prospective data from the Singapore Chinese Health Study, we previously reported that saturated fat was positively associated with early-stage colorectal cancer among women, with no association among men. Identifying overall patterns of diet that reflect actual eating habits can place individual nutrient findings into context, and can better inform public health dietary recommendations. METHODS. We analyzed the relation between dietary intake at baseline and colorectal cancer incidence in a population-based cohort of 63,257 men and women of Chinese ethnicity initiated in Singapore between 1993 and 1998. As of December 31, 2005, 961 incident colorectal cancer cases had been diagnosed. Food intake patterns were identified by principal components analysis. Component scores representing the level of intake of each pattern were used in Cox regression with adjustment for age at baseline, interview year, dialect group, education, diabetes, total energy intake, smoking, alcohol use, body mass index, physical activity and family history of colorectal cancer. RESULTS. Two distinct food patterns were identified: a “meat-dim sum” pattern characterized by pork and chicken dim sum foods, and a “vegetable-fruit-soy” pattern characterized by vegetables, fruit and tofu items. Total dietary fat was similarly correlated with each pattern, but correlations among fat subtypes varied. For example, the omega-3 and omega-6 fatty acids were moderately correlated with the vegetable-fruit-soy pattern, but not with the meat-dim sum pattern, whereas saturated fat intake was moderately associated with the meat-dim sum pattern, but not with the vegetable-fruit-soy pattern. There was no association with the vegetable-fruit-soy pattern for colorectal cancer, regardless of gender. The meat-dim sum pattern was associated with colorectal cancer among women, especially for localized disease. A U-shaped trend was observed, with the strongest association for third versus first quartile of intake [RR=1.84, 95% confidence interval (CI)=1.22-2.77]. Stratified analyses revealed a stronger association with shorter duration of follow-up (RR=2.00, 95% CI=1.03-3.89 with <5 years; RR=2.16, 95% CI=1.16-4.02 with 5-10 years; RR=1.09 95% CI=0.41-2.88 with >10 years). No association was observed among men. CONCLUSIONS. A diet high in meats, sodium, and refined carbohydrates may increase risk of colorectal cancer, particularly among women in this Singapore Chinese cohort. Identification of a dietary pattern associated with colorectal cancer is useful in providing a context for our individual nutrient findings that may be more meaningful for prevention strategies.