The prebiotic properties of oligofructose at low intake levels

Oligofructose and inulin, which are increasingly used in human food preparations, are now recognised as important prebiotic agents influencing the microbial composition of the gastrointestinal tract of the host. The specific objective of this study was to investigate the effect of ingesting a low dose of oligofructose (5 g/day) by healthy human subjects on the faecal microflora, especially bifidobacteria, and to compare it with the ingestion of a placebo (sucrose). In a placebo-controlled study design, faecal samples were collected in the morning from 8 healthy human subjects, who were not on any medication, and immediately enumerated for bifidobacteria, Bacteroides, coliforms, total anaerobes and total aerobes. Subjects first took sucrose (placebo) daily (5 g) for 3 weeks with their normal diet except for known sources of oligofructose and inulin and subsequently were administered oligofructose (5 g) daily for 3 weeks. Faecal samples were collected after 11 days and after 3 weeks. At 2 weeks post ingestion of oligofructose, another set of faecal samples was taken. All samples were subjected to immediate microbial enumeration. Ingestion of sucrose (5 g/day) was without effect on all faecal bacteria enumerated, whereas consumption of oligofructose (5 g/day) for 11 days resulted in close to one log cycle increase in bifidobacteria numbers. No further increase was observed after the next 10 days. At 2 weeks after termination of oligofructose ingestion, bifidobacteria numbers had decreased to almost that of the period before treatment. Increases in numbers of Bacteroides and total anaerobic bacteria but not in aerobic bacteria also occurred. (C) 2001 Elsevier Science Inc. All rights reserved.