Dietary factors and risk of colon cancer in Shanghai, China

Abstract

Colon cancer incidence rates have risen sharply in Shanghai, China, since the early 1970s, and diet may have contributed to the rising incidence. To clarify the role of dietary factors for colon cancer in Shanghai, we analyzed data from a population-based case-control study of 931 cases (462 males and 469 females) and 1552 controls (851 males and 701 females) ages 30-74 years in Shanghai, China, from 1990-1993. Subjects were interviewed in person for a detailed history of dietary practices and food preferences by using a food-frequency questionnaire. Colon cancer risk was estimated by odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for age, total energy, and other confounding factors. Risk for the highest versus the lowest quartile of intake was elevated for red meat (OR, 1.5; 95% CI, 1.0-2.1 for men and OR, 1.5; 95% CI, 1.0-2.2 for women), fish (OR, 1.7; 95% CI, 1.2-2.4 for men and OR, 1.2; 95% CI, 0.8-1.7 for women), and eggs (OR, 1.4; 95% CI, 1.0-1.9 for men and OR, 1.3; 95% CI, 0.9-1.9 for women), but was reduced for fresh fruit (OR, 0.7; 95% CI, 0.5-1.0 for men and OR, 0.6, 0.4-0.9 for women). High intake of preserved foods, whether animal or plant source, was associated with an excess risk of colon cancer (OR, 2.0; 95% CI, 1.5-2.9 for men and OR, 2.7; 95% CI, 1.9-3.8 for women). For dietary nutrients, risk generally declined with greater consumption of fiber and micronutrients common in fruit and vegetables, including vitamin C, carotene, and vitamin E. Intake of macronutrients in general was not significantly related to risk. Our findings suggest that diets high in fruit and antioxidant vitamins that are common in plant foods reduce the risk of colon cancer, whereas diets high in red meat, eggs, and preserved foods increase the risk.