['Many lactose maldigesters tolerate more lactose in experimental studies than in everyday life, in which their symptoms may result from other carbohydrates as well.', 'The question of whether the symptoms caused by large quantities of carbohydrates are more severe in lactose maldigesters than in control lactose digesters or in lactose digesters who report milk to be the cause of their gastrointestinal symptoms (pseudohypolactasic subjects) was studied in a randomized, double-blind, crossover study. Comparisons between commonly used diagnostic methods for lactose maldigestion were also made.', 'The subjects were 40 women aged 20-63 y from 3 groups: lactose maldigesters (n = 12), pseudohypolactasic subjects (n = 15), and control lactose digesters (n = 13). The subjects were given either 50 g lactose, 50 g sucrose, 25 g lactulose, or 25 g fructooligosaccharides. After carbohydrate ingestion, urine was collected and the breath-hydrogen concentration was measured every 30 min for 3 h. Blood glucose was measured every 20 min for 1 h and subjective gastrointestinal symptoms were monitored for 8 h with a questionnaire.', 'When lactulose and fructooligosaccharides were ingested, the lactose maldigesters (P = 0.04 and 0.09, respectively) and the pseudohypolactasic subjects (P = 0.006 and 0.01, respectively) reported more symptoms than did the control lactose digesters. Sucrose caused more symptoms in the lactose maldigesters than in the control lactose digesters (P = 0.05).'] Do fructooligosaccharides and lactulose cause more symptoms in lactose maldigesters and subjects with pseudohypolactasia than in control lactose digesters?