after ingestion of 6.5 , 13 , and 26 g of lactulose ( a nonabsorbable disaccharide ) , h ( 2 ) excretion increased linearly , averaging ( +/-1 sem ) 13+/-3.5 , 23+/-7.2 , and 49+/-7 ml per 2 hr .
C0022957
lactulose
C0012611
disaccharide