Purpose: The aim of this study was for the first time to assess the association between glycemic index (GI), glycemic load (GL), and colorectal cancer using a prospective Japanese population-based cohort.
Methods: In our study participants aged 40-69 at baseline of the Japan Public Health Center-based prospective Study (JPHC Study) in 10 prefectural public health centers (PHC) were included. Subjects responding to the five-year follow-up survey (1995-1999) without previous history of cancer and missing data were included in the current analysis n = 73,501 (men n = 34,560 and women n = 38,941). We reported results as hazard ratios (HR) and 95% confidence intervals (CI) by Cox proportional hazards modeling.
Results: The average follow-up time was 12.5 years (919,276 person-years). A total of 1,468 colorectal cancer cases were detected. Overall, no significant results were observed; however, GL was inversely nonsignificantly associated with colon cancer in men HR = 0.74 (95% CI 0.51-1.09) and rectal cancer in women 0.52 (95% CI 0.24-1.14). The GL tended to be inversely associated with proximal colon cancer among men 0.62 (95% CI 0.36-1.08), while a positive association with the GI was observed among women 1.37 (95% CI 0.88-2.14). Sensitivity analyses excluding the first three years of observation showed similar results. Results stratified by diabetes status, BMI, smoking and red meat were nonsignificant.
Conclusions: In conclusion, the prospective JPHC Study suggests that the GI and GL do not have a substantial impact on the risk of colorectal cancer in Japanese adults.
Keywords: Cohort study; Colorectal cancer; Glycemic index; Glycemic load; Japan.