Just taking probiotics won’t necessarily mean they actually take up residence in your gut.
Through a series of experiments looking inside the human gut, researchers from Israel show that many people’s digestive tracts prevent standard probiotics from successfully colonising them. In a second paper, they found that taking probiotics to counterbalance antibiotics could delay the return of normal gut bacteria to their original state.
The Science Media Centre gathered expert commentary on the paper. Please feel free to use these comments in your reporting.
Dr Olivier Gasser, Translational Immunology Team Leader, Malaghan Institute of Medical Research, comments:
“Antibiotic treatment creates a gaping ‘hole’ in the gut microbiome, an open niche that can very easily be colonised by good or bad bacteria. It is very important to close that hole as fast as possible, and if possible with a healthy set of bacteria. That the research finds probiotics seem to inhibit this process is a very important finding.
“For our work at the Malaghan Institute, a relevant clinical setting for this research is cancer immunotherapy. It is known that antibiotics treatment is detrimental to the efficacy of cancer immunotherapy. However, the same work has identified gut bacteria that boost immunotherapy. In that case, a cancer patient that receives antibiotics to potentially to limit a severe bacterial infection (i.e. clinically indicated), has a hole in their microbiome to be filled; and if not filled with the correct bacterial ecosystem, that patient might not benefit from a very expensive immunotherapy.
“A follow up review discusses the implications that probiotics could very well be, in the future, regulated at the same level as drugs (unlike over-the-counter dietary supplements, as they currently are), because the wrong strain could inflict harm while a beneficial one could have therapeutic effects, depending on the person taking them.
“This could be really the beginning of new legislation around probiotics, because worse case scenario, they’re not just doing nothing (while being expensive), but they may actually cause harm (although it’s important to note that the harm could manifest only later on, based on microbial dysbiosis).”
“It’s going to be interested to see how much effort is being put into recovering the patients’ microbiome after antibiotics treatment. I am not sure all health care providers are fully aware of the effects of antibiotics.
“I am not sure this would get a lot of traction (yet) for adults, but for infants (first 2 years of life), we know that antibiotics can have very significant long term side effects. In that setting, I hope that faecal microbiome transplant could one day be standard practice.
“No clinic is currently set up to harvest faecal matter and process it for faecal microbiome transplant (not via enema and certainly not via freeze/dried pill or capsules). This could open the door for businesses – there are already some on the web that offer that kind of thing.
“We don’t know exactly what constitutes a ‘healthy’ microbiome, so beyond faecal microbiome transplants, more research has to be carried out to determine what ‘healthy’ means. With blood donations, we test for infectious diseases and other blood-borne pathogens, but with faecal matter, we don’t know what proper quality control would look like.”
No conflict of interest.
Professor Gerald Tannock, microbiologist, University of Otago, comments:
“Probiotics, products containing live bacteria that upon consumption are believed to confer a health benefit, have been available commercially for more than a century.
“Despite widespread use of these ‘food supplements’, evidence of universal efficacy of this generic group of products has not been obtained. The misuse of the word ‘colonisation’ (inferring a state of permanent residence) of the bowel in relation to probiotic products is widespread, despite evidence from almost 20 years ago that, for most people, viable probiotic bacteria are only detected in faeces during the period in which the probiotic product is consumed.
“The authors of the Cell article extend research into the reason why probiotic bacteria do not colonise the human bowel by describing the bacterial collections associated with the gut lining in various locations within the digestive tract. They concluded that it is these bacterial collections that direct whether probiotic bacteria persist for longer or shorter periods in the human bowel.
“Their overall conclusion is that, given differences in mucosal bacterial populations between humans, probiotics are unlikely to be universally efficacious and that ‘tailor-made’ probiotics designed for specific diseases and even for specific people (personalised medicine) could be investigated. Whether this latter option could be available to more than an affluent few might be an interesting topic for discussion.
“Concerns about the potential of orally administered, life-saving, broad-spectrum antibiotics to disturb the composition of the normal bacterial community (microbiota) of the human bowel have been expressed. This ‘dysbiosis’ of the microbiota might have long term consequences on human health, especially if occurring in early life when the developing immune system and other aspects of physiology could be influenced by environmental factors.
“The reconstitution of the composition of the microbiota is of interest medically and commercially – especially the use of probiotic products during or after antibiotic treatment. Most antibiotic treatments are for no more than a week or so, but long-term treatment for chronic conditions can lead to the proliferation of toxin-producing bacteria in the bowel that results in serious disease.
The authors of the Cell article investigated the effect of probiotic consumption on recovery of the microbiota after a period of broad-spectrum antibiotic treatment. The experiment was not conducted in a clinical context – the people involved were healthy volunteers given a mixture of antibiotics.
“Surprisingly, the authors report that recovery of the microbiota was impaired by probiotic consumption (only one probiotic product was tested). Unexpected, because bacteria in probiotic products do not belong to the numerically predominant members of the human bowel microbiota and are not expected to persist long-term once administration has ceased. This result therefore needs confirmation in further studies.
“What was expected, and which did occur, was that administration of preparations of the volunteers own stool (faecal microbiota transfer/transplant) hastened the recovery of microbiota composition. The necessity of such procedures needs to be evaluated in the medical context of whether they confer sufficiently convincing benefits on patient well-being while outweighing any potential risks associated with dosing patients with an undefined mixture of faecal bacteria.”
No conflict of interest.