Associations of bread and pasta with the risk of cancer of the breast and colorectum.

BACKGROUND: Carbohydrate foods with high glycemic and insulinemic potential may influence cancer risk possibly through the insulin/growth-factor axis. Two staple carbohydrate foods of the Mediterranean diet, bread and pasta, have different glycemic and insulinemic responses and hence may affect cancer risk differently. MATERIALS AND METHODS: We studied the association of bread and pasta with breast and colorectal cancer risk using data from two Italian case-control studies. These studies included 2569 women with histologically confirmed breast cancer and 1953 men and women with colorectal cancer. Controls were 2588 and 4154, respectively, admitted to the same hospitals as cases for acute, non-neoplastic conditions. Multivariate odds ratios (ORs) were obtained after allowance for relevant confounding factors. RESULTS: The ORs of breast cancer for the highest versus the lowest quintile were 1.28 (95% confidence interval, CI: 1.03-1.58, P-trend = 0.0342) for bread and 1.07 (95% CI: 0.88-1.31, P-trend = 0.7072) for pasta. The association with bread remained virtually unchanged with postmenopause and overweight. The ORs of colorectal cancer in women for the highest versus the lowest quintile were 2.02 (95% CI: 1.46-2.80, P-trend = 0.0002) for bread and 1.37 (95% CI: 1.00-1.88, P-trend = 0.0164) for pasta. The associations remained significant only for bread in strata of menopausal status and in women with overweight. No significant associations were seen in men for either bread or pasta. CONCLUSIONS: Overall, these two cancer case-control studies showed stronger positive associations with bread than pasta in women, particularly if overweight, suggesting possible hormonal-related mechanisms.