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.