Carbohydrate, glycemic index, and glycemic load and colorectal adenomas in the Prostate, Lung, Colorectal, and Ovarian Screening Study.

BACKGROUND It is possible that high-glycemic-load diets, through their hyperinsulinemic effects, can increase the risk of colorectal cancer. OBJECTIVE We analyzed data from a cancer screening study to determine whether persons with high-glycemic-load diets would be at an increased risk of distal adenomas. DESIGN We included subjects with no prior adenoma or cancer from the Prostate, Lung, Colorectal, and Ovarian screening trial and whose results from flexible sigmoidoscopy exams indicated either no lesions (n = 34 817) or >/=1 distal adenoma (n = 3696). We used a 137-item food-frequency questionnaire to assess usual dietary intake over the preceding 12 mo. Using logistic regression analysis, we calculated, separately for men and women, prevalence odds ratios (ORs) and 95% CIs of sigmoidoscopy-detected, distal adenomas for quintiles of energy-adjusted dietary carbohydrate, glycemic index, and glycemic load. RESULTS ORs decreased with increasing intakes of carbohydrate for both the men and the women in unadjusted models, but these associations were attenuated in multivariate-adjusted models. Among the men, the association remained significant after adjustment (OR: 0.71; 95% CI 0.60, 0.84; P for trend < 0.0001), but in the women it did not (OR: 0.89; 95% CI: 0.73, 1.10; P for trend = 0.30). The results for glycemic index showed no associations in either men or women. Results for glycemic load closely mirrored those for carbohydrate. CONCLUSION Despite expectations that increasing glycemic load and glycemic index would increase the risk of adenoma, we observed no association in women and even an inverse association in men.