Relationship between lactose digestion, gastrointestinal transit time and symptoms in lactose malabsorbers after dairy consumption

Background: The relationship of symptoms with objective measurements, as well as some of the mechanisms involved in lactose tolerance after yoghurt consumption, remain unclear. Methods: The trial had a double-blind design in which 22 lactose malabsorbers received 25 g daily lactose in fresh (living bacteria > 10(8) cfu/g) yoghurt or heated (< 10(2) cfu/g) yoghurt for 15 days, followed by a cross-over (15 days) after a wash-out period (14 days). The lactose digestion was determined by the breath H-2 test, the gastric emptying (GE) with a C-13-acetate breath test and the revealed transit time (OCTT) by N-15-lactose-ureide test, Subjects reported their gastrointestinal symptoms (GIS) in a validated questionnaire. Results: Breath H-2 test indicated more effective lactose digestion after fresh yoghurt intake. The OCTT was shorter after heated yoghurt ingestion as compared with the fresh. There was lower severity of GIS (P < 0.05) after fresh yoghurt intake, and this showed an inverse correlation with OCTT (P < 0.05). Conclusions: Delayed orocoecal transit time was associated with fewer gastrointestinal symptoms. The improved lactose digestion and tolerance of fresh yoghurt should be mainly attributed to the presence of living bacteria.