The use of probiotics has become almost universally recommended. Two new studies advise caution on the blanket use of probiotics. Probiotics are beneficial in some patients but other patients may, unfortunately, have little response and even show adverse reactions to probiotics.
To summarize what we know:
- Stool samples alone do not provide an accurate picture of the interactions between probiotics and the patient’s pre-existing microbiome and their overall health
- Some patient’s microbiota resists colonization with probiotics while others change in response to probiotic ingestion and often in different ways along different points of the GI tract
- Probiotics after antibiotics can impede the microbiome’s return to baseline flora (significance unknown)
- Characteristics of an individual patient and their microbiome can predict probiotics effects in that person
- Using mice as a model for the human microbiome is not very informative or reliable in understanding the effects of probiotics
Probiotics, for a time now, have been recommended haphazardly and the decision to use them should be a medical decision (scientifically weighing the pros and cons), like the decision to use any medication or treatment. It should be a case-by-case decision, taking into account the long-term dysbiosis induced after taking probiotics after antibiotics and the knowledge that currently true indications for probiotics is limited.
What are needed are independently funded, multi-center, blinded, placebo-controlled studies on probiotics. This is a big divergence from manufacturer/pharma-sponsored studies with the currently held belief that probiotics effects are always positive.
These new studies show there is a lot that we do know about probiotics but also a lot we do not. For example, we know probiotics help when treating C. Difficile infection when given with antibiotics but if a person already has a C. Difficile infection, probiotics probably won’t help much.
In the first study, Zmora et at tested a multi-strain probiotic combination in both humans and mice. In the intervention group, 14 patients took the probiotics and 4 took a placebo and the other group received nothing. The study lasted a month. Stool samples were collected at baseline, daily for a week and then weekly for rest of the month of the study.
The findings show that the mucosal colonization patterns that emerged in the GI tract depended on the strain of the probiotic, the region of the body sampled and factors such as gene expression patterns in the gut and baseline microbiota. Further study of the stool did not describe nor predict the probiotic effect.
In the Suez study, three groups of patients each were studied after a seven-day course of Cipro and Flagyl. After the antibiotic course, one group received probiotics bid for 28 days, six received an autologous fecal transplant (taken before antibiotics) and seven had no further treatment. The study showed the patients on probiotics had a delayed microbiome recovery, the significance of which is currently unknown. Although, a persistent dysbiosis of the type induced by probiotics in the study has been linked to developing obesity, cardiometabolic disease and allergies.
In summary, the blanket use of probiotics for non-studied indications, may help in some patients, may do nothing in some patients and potentially harm others.
Personalized Gut Mucosal Colonization Resistance to Empiric Probiotics Is Associated with Unique Host and Microbiome Features Niv Zmora et al. Cell sept 6, 2018
Post-Antibiotic Gut Mucosal Microbiome Reconstitution Is Impaired by Probiotics and Improved by Autologous FMT Jotham Suez et al. Cell Sept 6, 2018