Is Carbohydrate Intolerance Associated With Carbohydrate Malabsorption in Disorders of Gut-Brain Interaction?

Introduction: We aimed to explore the prevalence of carbohydrate (lactose and fructose) intolerance in patients with disorders of gut-brain interaction (DGBI) and to characterize those patients regarding gastrointestinal and nongastrointestinal symptoms.

Methods: Patients with DGBI who were referred to the physiology unit of our hospital between May 2022 and December 2023 for lactose (25 g) and fructose (25 g) breath tests were prospectively included. Patients were required to have a negative glucose breath test, before lactose and fructose breath tests, and to have completed the adult carbohydrate perception questionnaire during each breath test. Intolerance was defined as an increase of ≥20 mm in the Visual Analog Scale score from baseline in at least 1 of the 5 symptoms (pain, nausea, bloating, flatulence, and diarrhea) assessed with the adult Carbohydrate Perception Questionnaire.

Results: Among the 301 patients with DGBI included in our analysis, 178 (59.1%) had carbohydrate intolerance. Carbohydrate-intolerant patients were significantly more likely to be female ( P value < 0.001), to have 2 or more DGBI ( P value = 0.001), to have lactose maldigestion ( P value< 0.001) and fructose malabsorption ( P value = 0.023), higher irritable bowel syndrome and somatic symptom severity, and lower quality of life ( P value < 0.001) compared with patients without carbohydrate intolerance. The binary logistic regression showed that lactose maldigestion ( P value = 0.001), as well as somatic symptoms ( P value = 0.025), were independently associated with carbohydrate intolerance (Nagelkerke R Square = 0.206).

Discussion: Carbohydrate intolerance affects a substantial group of patients with DGBI, affecting their quality of life and symptom severity. Further research is needed to explore the underlying mechanisms in patients who do not have carbohydrate malabsorption/maldigestion.