Fructose Malabsorption, Gut Microbiota and Clinical Consequences: A Narrative Review of the Current Evidence.

Fructose malabsorption is characterized as the incomplete absorption of fructose in the small intestine. Fructose is one of the most common monosaccharides in the human diet. The purpose of this review is to provide an updated overview of insights into the relationship between high-fructose diet, fructose malabsorption, gut microbiota and clinical consequences. Incomplete absorption of fructose causes accumulation in the colon, which leads to fermentation by gut microbiota and abdominal symptoms such as bloating and excessive gas production. Malabsorption may result from exceeding the absorptive capacity of GLUT5 or insufficient upregulation, with incidence increasing with age and higher dietary fructose concentrations. High-fructose diets generally promote an increase in inflammatory bacterial groups such as Desulfovibrio and Deferribacteraceae, while reducing beneficial Bacteroidetes. These microbial alterations may impair intestinal barrier function, modify short-chain fatty acid profiles, and contribute to systemic inflammation, metabolic disorders, and potentially mental health issues. Animal studies using fructose malabsorption models present inconclusive results regarding the impact of fructose on the composition of gut microbiota. Additional research is essential to fully comprehend the complex relationship between diet, fructose malabsorption and gut microbiota, to develop personalized, effective dietary approaches for managing symptoms of fructose malabsorption.