Dietary glycemic index, glycemic load, and risk of breast cancer: meta-analysis of prospective cohort studies

Consumption diets of high glycemic index (GI) and glycemic load (GL) may increase the risk of breast cancer. We aimed to conduct a meta-analysis of prospective cohort studies to evaluate the associations between dietary GI and GL and risk of breast cancer. We searched the PubMed database for relevant studies through November 2010, with no restrictions. We included prospective cohort studies that reported relative risk (RR) with 95% confidence intervals (CIs) for the associations of dietary GI and GL with breast cancer risk. Summary RRs were calculated using both fixed- and random-effects models. We identified 10 prospective cohort studies eligible for analysis, involving 15,839 cases and 577,538 participants. The summary RR of breast cancer for the highest GI intake compared with the lowest was 1.08 (95% CI: 1.02-1.14), with no evidence of heterogeneity (P = 0.72, I (2) = 0%). For GL, the summary RR was 1.04 (95% CI: 0.95-1.15), and substantial heterogeneity was observed (P = 0.02, I (2) = 55.6%). The GI and GL and breast cancer associations did not significantly modified by geographic region, length of follow-up, number of cases, or menopausal status at baseline. Dose-response analysis was not performed due to limited number of eligible studies. There was no evidence of publication bias. In summary, the present meta-analysis of prospective cohort studies suggests that high dietary GI is associated with a significantly increased risk of breast cancer. However, there is no significant association between dietary GL and breast cancer risk.