DIET AND RISK OF COLORECTAL ADENOMAS - MACRONUTRIENTS, CHOLESTEROL, AND FIBER

Background: Diet is thought to be important in the etiology of colorec tal cancer. Studies suggest that a diet high in red meat and saturated fat and low in dietary fiber and vegetables may increase cancer risk. Diet may also be important in the development of colorectal adenomas that are precursors of most colorectal cancers, but this hypothesis ha s not been well studied. Purpose: This case-control study was designed to examine the effects of dietary consumption of cholesterol, fiber ( vegetables, fruits, beans, and grains), and macronutrients (protein, c arbohydrate, and fat) on risk for colorectal adenomas. Methods: Analys es were based on data from 236 subjects (105 men and 131 women) with h istologically confirmed adenomas (cases) and 409 adenoma-free control subjects (165 men and 244 women), all of whom had had colonoscopy. Cas e and control subjects were similar with respect to gender, body mass, race, marital status, education, and indications for colonoscopy. Usi ng a validated quantitative food-frequency questionnaire, an experienc ed graduate nutritionist interviewed each subject by telephone. Sex-sp ecific analyses were conducted because the ranges of nutrient intake w ere substantially different for men and women. Odds ratios (ORs) were calculated according to quintiles of nutrient intake. Results: Carbohy drate intake was inversely related to adenoma risk in women (P for tre nd = .002). Compared with women in the lowest quintile of carbohydrate consumption, those in the highest quintile were 60% less likely to de velop adenomas (OR = 0.39; 95% confidence interval [CI] = 0.19-0.80). Intake of fruit (P for trend = .028) and intake of fiber derived from vegetables and fruits (P for trend = .012) were also inversely related to adenomas in women. Total fat showed a positive association in wome n (P for trend = .004), with an OR of 2.69 for the highest versus the lowest quintile (95% CI = 1.31-5.50). Results were comparable for satu rated fat (P for trend = .027). The risks in men were generally simila r in direction and magnitude but were not statistically significant. C onclusions: These data support the hypothesis that a diet high in fat and low in carbohydrates, fruits, and fruit and vegetable fiber increa ses risk not only for colorectal cancer but also for precursor colorec tal adenomas. Implications: These results, which are consistent with f indings of other investigators, suggest that environmental factors inf luencing risk for colorectal cancer, such as a high-risk diet, may lea d to development of the precursor adenomas.