Abstract
The effect of dietary supplementation with lactulose (3 g/d for 2 wk) on the faecal flora and faecal bacterial metabolism was studied in eight healthy volunteers. During the intake of lactulose, the number of bifidobacteria increased significantly (P<0.01), whereas the numbers of lecithinase-positive clostridia, including Clostridium perfringens, and Bacteroidaceae decreased (P<0.05) compared to values before and after the intake. Faecal indole, skatol and phenols, and faecal β-glucuronidase, nitroreductase and azoreductase activities were decreased significantly (P<0.05) after 7–14 d of treatment. Mean faecal pH decreased from 70 to 6.4, and water content increased 3.5–5.3 per cent during lactulose ingestion.