Higher dietary glycemic index, but not glycemic load, is associated with increased risk of ulcerative colitis: a prospective cohort study

Background and Aims Total carbohydrate intake has been inconsistently associated with inflammatory bowel disease (IBD) risk in previous epidemiological studies. We aimed to evaluate the effects of glycemic index and glycemic load, 2 main indicators for measuring the quality and quantity of carbohydrates, on the risk of IBD subtypes (ie, Crohn's disease [CD] and ulcerative colitis [UC]).Methods We included 121 148 UK Biobank participants without IBD at baseline, and collected dietary information from a validated web-based 24-hour dietary recall questionnaire. Overall dietary glycemic index and glycemic load were estimated. Cox proportional hazard models were used to calculate multivariable-adjusted hazard ratios (HRs) and 95% CIs. Substitution analyses were conducted to test associations after replacing medium- or high-glycemic-index foods with low-glycemic-index foods.Results During a median follow-up of 10.6 years, 133 incident CD and 335 incident UC cases were identified. Dietary glycemic index was associated with UC but not CD. The HR of UC was 1.13 (95% CI, 1.01-1.27) per 1-SD increment and 1.46 (95% CI, 1.07-1.99) for the highest versus lowest quartile of glycemic index. Replacing medium or medium- and high-glycemic-index foods with low-glycemic-index foods was associated with a lower risk of UC. No significant associations were found between dietary glycemic load with risk of CD and UC.Conclusions A higher dietary glycemic index, but not glycemic load, is associated with an increased risk of UC, underscoring the importance of considering glycemic index in dietary recommendations for UC prevention.