A double-blind placebo-controlled study to establish the bifidogenic dose of inulin in healthy humans.

OBJECTIVE

To evaluate the bifidogenic efficacy of two inulin doses in healthy human adults.

DESIGN

A double-blind, placebo-controlled, crossover human study.

SETTING

Food Microbial Sciences Unit, The University of Reading, Reading, UK.

SUBJECTS

Thirty healthy volunteers, 15 men, 15 women (age range 19-35).

INTERVENTIONS

Subjects consumed a chocolate drink containing placebo (maltodextrin, 8 g/day), 5 g/day inulin and 8 g/day inulin for a 2-week treatment period. Each treatment was followed by a 1-week washout at the end of which volunteers progressed to the next treatment. Faecal samples were obtained at the start of the study (baseline) and at the end of each treatment and washout period. Fluorescent in situ hybridization was used to monitor populations of Bifidobacterium genus, Bacteroides - Prevotella, Lactobacillus - Enterococcus and Clostridium perfringens - histolyticum subgroup.

RESULTS

Bifidobacterial levels increased significantly upon ingestion of both the low (9.78+/-0.29 log(10) cells/g faeces, P<0.05) and the high inulin dose (9.79+/-0.38 log(10) cells/g faeces, P=0.05) compared to placebo (9.64+/-0.23 log(10) cells/g faeces).

CONCLUSIONS

Both inulin doses exhibited a bifidogenic effect but a higher volunteer percentage responded to the high dose. A dose response effect was not observed but the magnitude of increase in bifidobacteria levels depended on their initial numbers. The higher the initial concentrations the smaller was the increase upon ingestion of the active treatments.