Composition and metabolism of the intestinal microbiota in consumers and non-consumers of yogurt.

The objective of the present study was to evaluate the impact of a regular consumption of yogurt on the composition and metabolism of the human intestinal microbiota. Adult subjects were selected on the basis of daily food records and divided into two groups: yogurt consumers (at least 200 g yogurt consumed per d, n 30); non-consumers (no yogurt, it 21). Their faecal microbiota was analysed using molecular methods (in situ hybridisation and PCR amplification combined with separation by denaturing gel electrophoresis) and its metabolic characteristics were assessed by measuring glycosidase, P-glucuronidase and reductase activities and profiling SCFA, neutral sterols and bile acids. The yogurt starter Lactobacillus delbrueckii ssp. bulgaricus (identity confirmed by 16S rRNA sequencing) was detected in 73 % of faecal samples from fermented milk consumers v. 28 % from non-consumers (P= 0.03). In yogurt consumers, the level of Enterobacteriaceae was significantly lower (P= 0.006) and beta-galactosidase activity was significantly increased (P=0.048). In addition, within this group, P-galactosidase activity and the Bifidobacterium population were both positively correlated with the amount of fermented milk ingested (r 0.66, P < 0.0001 and r 0.43, P= 0.018, respectively). Apart from these effects, which can be considered beneficial to the host, no other major differences could be detected regarding the composition and metabolic activity of intestinal microbiota.