Glycemic index, glycemic load, and colorectal cancer risk stratified by insulin receptor expression: the Japan Public...

Glycemic index (GI) and glycemic load (GL) are markers for postprandial glucose level. Since insulin, a hormone secreted to control hyperglycemia, is likely to promote the progression of tumor cells, the association between GI/GL and risk of colorectal cancer (CRC) has been researched for decades but still remains controversial. This study investigated the association between GI/GL and CRC risk, considering subtypes based on insulin receptor beta (IRβ) expression.

In a large-scale, population-based prospective cohort study involving 18,537 Japanese participants, a total of 415 CRC cases were evaluated for IRβ expression using immunohistochemistry. GI and GL were calculated using a validated food frequency questionnaire. The Cox proportional hazards model was used to assess the hazard ratios (HRs) and 95% confidence intervals (CIs) of the risk of CRC and its specific subtypes. Additionally, we conducted sensitivity analyses to confirm the robustness of the results.

No significant associations were observed between dietary GI, GL and overall CRC risk. Further, no significant associations were detected in IRβ-stratified analyses. The heterogeneities in the associations by IRβ status were also not statistically significant. (GI: p for heterogeneity 0.83 for men and 0.96 for women; GL: p for heterogeneity 0.84 for men and 0.60 for women) Sensitivity analyses yielded robust results.

This study did not observe a significant association between GI/GL and overall CRC or IRβ-defined subtypes. These results, particularly those from the assessment of IRβ status, do not support a possible association between GI/GL and CRC development.