Probiotics may not be as beneficial as previously thought

According to a recent study, after the administration of an antibiotic, probiotics would not have the expected beneficial effect on the regeneration of the intestinal flora. On the contrary, they would delay the return of a balanced microbiota, according to new studies.

Indeed, researchers found that not only would probiotics have a very limited effect in a healthy individual, but they could also prevent the natural flora from settling after taking antibiotics. These findings are the result of two recent studies recently published in the journal Cell.

Probiotics are products – often in capsule form – containing millions of live bacteria as well as compounds to help bacteria grow (called prebiotics). Their goal is to colonize the intestines of the consumer to restore the balance of the microbiota (or intestinal flora), undermined by poor nutrition or antibiotics, for example. Some probiotics aim to colonize other areas of the body that have a specific microbiota, such as the vagina or the mouth. Probiotics are increasingly prescribed and consumed, attracting consumers, even healthy ones, to relieve gastrointestinal symptoms, strengthen the immune system, protect against infectious diseases, etc. “However, we still lack evidence of such impacts of probiotics on humans,” write the authors of the publications.

The team of researchers conducted two projects, to evaluate the effect of probiotics in a healthy individual, then in an individual whose intestinal flora was damaged by antibiotics – a major indication of probiotics.

To evaluate the effects, the researchers examined the intestines of 25 volunteers through endoscopies of the digestive system and colonoscopies. They were able to sample their basic microbiome, that is to say the environment in which all of the many organisms found inside their body, called microbiota, live. Fifteen of these volunteers were then divided into two groups: one consumed multi-stem probiotics and another ingested a placebo. Three weeks later, both groups again performed endoscopy and colonoscopy to assess their internal response. They were followed for two months.

Results: Probiotics have successfully colonized the gastrointestinal tract of some people, called the “persistent”, while the intestinal microbiomes of the “resistant” expelled them. “Surprisingly, we saw that many healthy volunteers were actually resistant to the extent that probiotics could not colonize their gastrointestinal tract,” Eran Elinav says. This suggests that probiotics should not be universally given as a “unique” supplement. Instead, they could be adapted to the needs of each individual. ”

For the second part of the trial, scientists looked at whether probiotics were able to counter the adverse effects of antibiotics. In theory, probiotics are supposed to repopulate the gut microbiota weakened by the treatment. The researchers observed the intestines of 21 volunteers who received antibiotics, also with endoscopies of the digestive system and colonoscopies.

These volunteers were then randomly divided into three groups. The first was a surveillance group that allowed its microbiome to 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 faecal microbiome transplant (aFMT). It contain the bacteria present in the intestinal flora before its alteration, and can rebalance the latter.

After the disappearance of antibiotics in the body, the team of researchers found that the probiotics had easily colonized the intestine of all members of the second group. But to their surprise, this probiotic colonization prevented the intestinal microbiome of the host from returning to its normal state for months. In contrast, with the aFMT, the native intestinal microbiome of the third group returned to normal in a few days.

“Contrary to the current dogma that probiotics are harmless and benefit everyone, these results reveal an adverse, potentially alarming side effect of using probiotics with antibiotics, which could even have long-term consequences,” alert the lead author of the study. The researchers stress the need to develop personalized approaches to the prescription of probiotics, to protect the intestinal mucosa without compromising the recolonization of the microbiome disturbed by antibiotics.

Shakes Gilles

Editor of The Talking Democrat. He enjoys bike riding, kayaking and playing soccer. On a slow weekend, you'll find him with a book by the lake.