Unraveling how probiotic yogurt works

No matter what the advertisements are, or are not, allowed to say, it would be good to know if probiotic yogurt, in addition to its nutritional value, has a beneficial effect on the gut. In this issue, McNulty, Gordon and their colleagues describe a parallel series of human and animal studies designed to uncover the effects of probiotic yogurt on the gut microbiota. The intake of yogurt supplemented with five bacterial species, including the probiotic Bifidobacterium animalis, did not appreciably alter the composition of the human or mouse gut microbiota, but it did induce transcriptional and metabolic changes that reflected host bacterial responses to the arrival of the new species. This elegant study provides a strategy to delineate the precise effects exerted by probiotic foods on the human gut.