Specific malabsorption of carbohydrate is related to the lack or decrease in enzymatic activity needed for its hydrolysis; seldom, it is related to the lack or overloading in transport mechanism of monosaccharide. Ingestion of unabsorbed carbohydrate may induce digestive symptoms due to its colonic fermentation (borborygmus, bloating, pain, and flatus) or its osmotic activity (diarrhoea). In a patient consuming at least a bowl of milk per day and suffering of functional digestive symptoms, intolerance to lactose must be ruled out because its treatment is easy and efficient, i.e. to put fermented dairy products in place of milk.