High-throughput 16S ribosomal RNA gene sequencing was used to characterize the fecal microbiota in healthy adults ( 23-55 y old ) of both sexes , before and after 4 wk of daily consumption of a capsule containing at least 24 billion viable Lactobacillus paracasei DG cells , according to a randomized , double-blind , crossover placebo-controlled design .