Probiotics are live bacteria that boost the immune system and prevent disease by colonizing the good bacteria found naturally along the digestive tract. They are also widely prescribed to compensate for the undesirable effects of antibiotics (digestive discomfort, diarrhoea, etc.). But new research suggests they may not be as effective as expected. Researchers from the Weizmann Institute of Science in Israel recently conducted a study published in Cell to determine their effectiveness.
“People have been very supportive of probiotics, even though the literature behind their understandings is very controversial, Explain in a Science Daily article Eran Elinav, lead author of the study. We wanted to determine if probiotics such as the ones you buy [en pharmacie en France, ndlr] colonize the gastrointestinal tract as they are expected to, and whether these probiotics impact the human host. »
Probiotics adapted to each individual
In order to assess the effects, the researchers examined the intestines of 25 volunteers through endoscopies of the digestive system and colonoscopies. They were thus able to sample their basic microbiome, that is to say the environment in which all the many organisms found inside their body live, called microbiota. Fifteen of these volunteers were then divided into two groups: one consumed multi-strain probiotics and another ingested a placebo. Three weeks later, both groups performed endoscopy and colonoscopy again to assess their internal response. They were then followed for two months.
Results: Probiotics successfully colonized the gastrointestinal tracts of some people, called the “persistent”, while the gut microbiomes of the “resistant” expelled them. “Amazingly, we saw that many healthy volunteers were actually resistant to the extent that probiotics could not colonize their gastrointestinal tracts, develops Eran Elinav. This suggests that probiotics should not be universally given as the “only” supplement. Instead, they could be tailored to each individual’s needs. »
Probiotics and Antibiotics
For the second part of the trial, the scientists investigated whether probiotics were able to counter the adverse effects of antibiotics. In theory, probiotics are supposed to repopulate the intestinal microbiota weakened by the treatment. The researchers thus observed the intestines of 21 volunteers who had received antibiotics, also with endoscopies of the digestive system and colonoscopies.
These volunteers were then randomly divided into three groups. The first was a monitoring group that let its microbiome recover on its own. The second group received the same probiotics used in the first part of the study. The third group was treated with an autologous fecal microbiome transplant (aFMT). This involves collecting their own stools before the administration of antibiotics, to reinject them into the intestines. They contain the bacteria present in the intestinal flora before its alteration, and can thus rebalance the latter.
“A bad side effect”
After the antibiotics disappeared from the body, the research team found that the probiotics easily colonized the gut of all members of the second group. But to their surprise, this probiotic colonization prevented the host’s gut microbiome from returning to its normal state for months. In contrast, with aFMT, the native gut microbiome of the third group returned to normal within days.
“Contrary to the current dogma that probiotics are harmless and beneficial to everyone, these findings reveal a potentially alarming adverse side effect of using probiotics with antibiotics that may even have long-term consequences”, warns the main author of the study. The researchers therefore underline the need to develop personalized approaches to the prescription of probiotics, to protect the intestinal mucosa without compromising the recolonization of the microbiome disrupted by antibiotics.
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