Dietary glycemic index and glycemic load in relation to risk of breast cancer.

OBJECTIVE Previous studies on the association between glycemic index (GI) and load (GL) in relation to breast cancer risk are contradictory. The aim of this study was to examine the association between dietary GI and GL and risk of breast cancer in Iranian women. DESIGN Population-based case-control. Dietary GI and GL were assessed using a validated Willett-format 106-item semi-quantitative food frequency questionnaire. SETTING Isfahan, Iran. PARTICIPANTS Cases were 350 patients with newly diagnosed stage I-IV breast cancer, for whom the status of breast cancer was confirmed by physical examination and mammography. Controls were 700 age-matched apparently healthy individuals who were randomly selected from general population. RESULTS After controlling for potential confounders, individuals in the highest tertile of dietary GI had 47% higher odds of breast cancer than women in the lowest tertile (OR: 1.47; 95% CI: 1.02-2.12). Stratified analysis by menopausal status showed such association among postmenopausal women (OR: 1.51; 95% CI: 1.02-2.23). We found no significant association between dietary GL and odds of breast cancer either before (OR: 1.35; 95% CI: 0.99-1.84) or after adjustment for potential confounders (OR: 1.24; 95% CI: 0.86-1.79). In addition, stratified analysis by menopausal status revealed no significant association between dietary GL and odds of breast cancer. CONCLUSIONS Our findings showed a significant positive association between dietary GI and odds of breast cancer. However, we observed no significant association between dietary GL and odds of breast cancer.