New publications
Probiotic yogurts do not have a positive effect on gut microflora
Last reviewed: 30.06.2025
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
If the bacteria contained in yoghurts have a positive effect on the human intestinal microflora, they do so in a way that is incomprehensible to science. Researchers have failed to detect the slightest shift in the human intestinal microflora after systematic consumption of probiotic yoghurts.
And how advertising is done! "The bacteria contained in the product will help you restore the microflora and normalize the work of the intestines"... The irony is that if the bacteria in yogurt do help, then in some unknown way, about which science knows nothing. Microbiologists from Washington University in St. Louis (USA) came to the conclusion that the bacteria in yogurts do not have any effect on the microflora of the gastrointestinal tract and are certainly not able to replace it.
The researchers recruited seven pairs of identical twins for the study. One twin in each pair, while on the same diet, regularly ate a popular brand of yogurt containing five bacterial strains. Because the twins were genetically identical, the influence of factors other than diet on the gut microbiome was minimized.
After some time, microbiologists conducted a DNA analysis of the intestinal microflora of volunteers. It turned out that lactic acid bacteria from yogurt did not affect the species composition of the "native" bacteria. Jeffrey Gordon, the project manager, said that he was not surprised by the results of the study. The intestines are home to tens of trillions of bacteria, and the several billion that arrive with yogurt are unlikely to somehow affect the established system of human intestinal microflora.
The results were confirmed in animal experiments. The scientists obtained gnotobiotic mice, deprived of their own microflora, and introduced 15 species of microorganisms that live in humans into their intestines. After that, the mice were again fed yogurt bacteria. And again, the yogurt bacteria had no effect on the composition of the animals' established intestinal microflora. However, as the scientists write in the journal Science Translational Medicine, they were able to detect changes in the genetic activity of the resident bacteria: their activity of genes responsible for carbohydrate processing increased. The same increase in activity was observed after entering the intestines of one of the "external" bacteria, Bifidobacterium animalis lactis.
Recently, manufacturers who are engaged in the creation and promotion of "bioactive" products have increasingly come under criticism, demanding confirmation of the usefulness and "bioactivity" of yoghurt products. But the fact is that it is quite difficult to select an adequate experimental system that would evaluate its effect on the same microflora. Gnotobiont animals could serve in this matter, since in this case all the factors that affect their microflora are under the control of the researcher. But, as you can see, you need to be prepared for the fact that not all yoghurts will be equally useful.
So far, objections to the results come down to the fact that too few people took part in the study, and a sufficiently detailed analysis of bacterial DNA was not carried out. As for animal experiments, here they point out that the intestines of mice are still adapted to the habitation of their own, and not imposed (human) microflora. It is possible that bacteria from yogurt do have a positive effect on human well-being, but science knows nothing about this.