High glycemic index and glycemic load are associated with moderately increased cancer risk

Scope: To obtain an up-to-date quantification of the association between dietary glycemic index (GI) and glycemic load (GL) and the risk of cancer. Methods and results: We conducted a systematic review and meta-analysis of observational studies updated to January 2015. Summary relative risks (RRs) were derived using random effects models. Seventy-five reports were evaluated in the systematic review (147 090 cases), and 72 were included in the meta-analyses by cancer site. Considering hormone-related cancers, summary RRs comparing the highest versus the lowest GI and GL intake were, respectively, 1.05 and 1.07 for breast, 1.13 and 1.17 for endometrial, 1.11 and 1.19 for ovarian, and 1.06 and 1.04 for prostate cancers. Considering digestive-tract cancers, summary RRs for GI and GL were, respectively, 1.46 and 1.25 for esophageal (squamous cell carcinoma), 1.17 and 1.10 for stomach, 1.16 (significant) and 1.10 for colorectal, 1.11 and 1.14 for liver, and 1.10 and 1.01 for pancreatic cancers. In most of these meta-analyses, significant heterogeneity among studies was observed. In subgroup analyses, case-control studies and studies from Europe tended to estimate higher RRs. Conclusion: High-GI and high-GL diets are related to moderately increased risk of cancer at several common sites.