Baseline microbiota activity and initial bifidobacteria counts influence responses to prebiotic dosing in healthy subjects

Summary Background Dietary intervention with prebiotics can cause changes in the colonic microbiota and their metabolic activities. Aim To investigate whether the response to prebiotic dosing is influenced by the baseline metabolic activity of the colonic flora and bifidobacteria counts. Methods The 4‐week effect of lactulose (10 g bid.; n = 29) and oligofructose‐enriched inulin (10 g bid.; n = 19) was evaluated in healthy human volunteers. Lactose‐[15N, 15N]‐ureide was used to study the colonic NH3‐metabolism. Urine (48 h) and faeces (72 h) were collected and analysed for p‐cresol and 15N‐content by gas chromatography–mass spectrometry and isotope ratio mass spectrometer, respectively. Faecal bifidobacteria were quantified by real‐time polymerase chain reaction. Results After the 4‐week prebiotic administration period, the urinary excretion of p‐cresol and 15N was significantly decreased in both groups (P