The association of carbohydrate intake, glycemic load, glycemic index, and selected rice foods with breast cancer risk: a case-control study in South Korea.

Despite carbohydrate hypothesis related to breast cancer development, the inter-relationships of carbohydrate measures with risk of breast cancer are unclear. We evaluated the association between the risk of breast cancer and total carbohydrate intake, glycemic load, and glycemic index, and types of rice in a hospital-based case-control study. Cases were 362 women aged 30-65 years old who were histologically confirmed to have breast cancer. Controls visiting the same hospital were matched to cases according to their age (+/-2 years) and menopausal status. Food intake was estimated by a quantitative food frequency questionnaire (FFQ) with 121 items. Conditional and unconditional logistic regression analysis was used to obtain the odds ratios (ORs) and corresponding 95% confidence intervals. There were no associations between risk of breast cancer and carbohydrate intake and glycemic load. A positive association with white rice (OR=1.19 per 100g/d increment, 95% confidence interval (CI)=1.01-1.40), no association with mixed white rice (OR=0.95 per 100g/d increment, 95% CI=0.80-1.13), and an inverse association with mixed brown rice (OR=0.76 per 100g/d increment of mixed brown rice, 95% CI=0.61-0.95) was found. Additional analysis showed a positive association for white rice and an inverse association f mixed brown rice with breast cancer risk among overweight, postmenopausal women. These results do not support an association between breast cancer and diets high in carbohydrate, glycemic index, or glycemic load. However, a higher consumption of mixed brown rice may be associated with a decreased risk of breast cancer, especially in overweight, postmenopausal women.