Dietary glycemic index and glycemic load, and breast cancer risk: A case-control study

Background: Certain types of carbohydrates increase glucose and insulin lev els to a greater extent than others. In turn, insulin may raise levels of i nsulin-like growth factors, which may influence breast cancer risk. We anal yzed the effect of type and amount of carbohydrates on breast cancer risk, using the glycemic index and the glycemic load measures in a large case-con trol study conducted in Italy. Patients and methods: Cases were 2569 women with incident, histologically-c onfirmed breast cancer interviewed between 1991 and 1994. Controls were 258 8 women admitted to the same hospital network for a variety of acute, non-n eoplastic conditions. Average daily glycemic index and glycemic load were c alculated from a validated 78-item food frequency questionnaire. Results: Direct associations with breast cancer risk emerged for glycemic i ndex (odds ratio, OR for highest vs. lowest quintile = 1.4; P for trend <0. 01) and glycemic load (OR = 1.3; P < 0.01). High glycemic index foods, such as white bread, increased the risk of breast cancer (OR = 1.3) while the i ntake of pasta, a medium glycemic index food, seemed to have no influence ( OR = 1.0). Findings were consistent across different strata of menopausal s tatus, alcohol intake, and physical activity level. Conclusions: This study supports the hypothesis of moderate, direct associa tions between glycemic index or glycemic load and breast cancer risk and, c onsequently, a possible role of hyperinsulinemia/insulin resistance in brea st cancer development.