Glycemic index, glycemic load and thyroid cancer risk.

BACKGROUND Risk of thyroid cancer has already been related to refined cereals and starch food, but the association has not been studied in terms of glycemic index (GI) and glycemic load (GL). PATIENTS AND METHODS We analyzed data from a case-control study conducted in Italy from 1986 to 1992 and including 399 histologically confirmed and incident cases of thyroid cancer and 616 control subjects. Information on dietary habits was derived through a food-frequency questionnaire and multivariate odds ratios (ORs) for GI and GL levels were estimated with adjustment for age, education, sex, area of residence, history of diabetes, body mass index, smoking, alcohol consumption, intake of fruit and vegetables, and noncarbohydrate energy intake. RESULTS Compared with the lowest tertile, the ORs in subsequent tertiles were 1.68 and 1.73 for GI, and 1.76 and 2.17 for GL. The OR for highest tertile of GI compared with lowest one was 1.70 for papillary and 1.57 for follicular thyroid cancer. The ORs for GL were 2.17 for papillary and 3.33 for follicular thyroid cancer. CONCLUSION Our study shows that high dietary levels of GI and GL are associated with thyroid cancer risk.