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In late 2018, a respected scientific journal published two papers on probiotics that left scientists scratching their heads. In a nutshell, they claimed that probiotics were pretty much useless in the face of antibiotics. Some global media extrapolated further, reporting that the journal had said probiotics were not only useless, but harmful.
Let’s take a dive into one of the studies.
Suez et al. (2018) researched 21 participants, with only eight included in the probiotic group. (A small and unreliable sample size by clinical standards.)
Participants were given antibiotics to wipe out their gut microbiome and later took probiotics. The study reported that participants’ microbiota had not recovered after five months. Whether they drank, smoked or ate junk food before, during and after the trial is unknown, which is important, because these lifestyle factors can have a big influence on the gut.
Participants were given a random product found on shelf containing 11 ‘species’ of bacteria. ‘Species’ are a broader classification of bacterial ‘strains’ and are generally not studied for such specific health outcomes. So why test a very general product that suggested from the outset that it might not prove effective?
Putting this aside, the instructions on pack stated: “Should be taken two hours after taking antibiotics,” yet participants were instructed to take the probiotics seven days after the completion of antibiotics.
A 2017 review (Shen et al.) of 19 trials including 6,261 patients suggests that giving probiotics within a maximum of two days of antibiotic use is far more effective than starting later. The earlier the better.
In the only study of the 19 trials that gave probiotics seven days after antibiotics, the researchers found the longer than recommended delay would have blunted any effects of the probiotics. Equally, the studies that required earlier administration found significantly greater efficacy.
While we support original thinking in science, two peer-reviewed papers do not represent the balance of available evidence and should not nullify the large volume of research that has come before them.
It’s important to remember that it’s the positive balance of evidence, and not one or two cherry-picked studies, that will conclude the effectiveness of probiotics.