The capacity of nondigestible carbohydrates to stimulate fecal bifidobacteria in healthy humans:: a double-blind, randomized, placebo-controlled, parallel-group, dose-response relation study

Background: Nondigestible carbohydrates (NDCHs) are fermented in the colon, where they can selectively promote the growth of bifidobacteria. Objective: Our aim was to determine the bifidogenic potential of different NDCHs used in human diets. Design: Two hundred healthy volunteers participated in this double-blind study. During phase 1 (screening), 64 volunteers were randomly assigned to 8 groups of 8 subjects each; for 7 d, they ingested 10 g/d of 1 of the 7 NDCHs tested or of the placebo. During phase 2 (dose-response study), 136 volunteers were randomly assigned to 4 groups of 32 subjects who received 2.5, 5.0, 7.5, or 10 g/d, respectively (8 subjects/dose), of one of the NDCHs that were proven to be bifidogenic during phase 1 and a fifth group of 8 subjects (control subjects) who received the placebo. Stools were recovered before and after NDCH consumption. Results: In phase 1, 4 NDCHs were found to be bifidogenic: short-chain fructooligosaccharides (P = 0.008), soybean oligosaccharides (P = 0.006), galactooligosaccharides (P < 0.0001), and type III resistant starch (P = 0.02); lactulose, long-chain inulin, and isomalto-oligosaccharides were not bifidogenic. In phase 2, the effects of 7-d treatment on bifidobacteria concentrations were found to differ significantly among the 4 NDCHs (P = 0.009 for time x treatment interaction). However, no significant differences were found among doses, and there was no significant dose x time interaction. A low baseline bifidobacteria count was significantly associated with the bifidogenic response to treatment (P < 0.001). Conclusion: This study showed the different bifidogenic properties among the substrates and underlined the importance of taking into account the baseline bifidobacteria counts when evaluating the effect of the treatment.