Over the last two weeks or so, there’s been a lot of negative press about probiotics. We’ve been through this before though, you and I…and I’m sure we’ll go through it again. Some study or another makes a controversial claim and the media jumps all over it because it grabs people’s attention. I’ve waffled about covering this whole hoopla but finally decided I should since Biome Buzz readers are always the most up-to-date on all the biome happenings!
So here is a brief overview of the two papers that have caused such an uproar:
A team at the Weizmann Institute in Israel (which, actually, produces some of the best biome research in recent years) did a 4 week study on 15 people – so a tiny sample size, short time frame – and found that in some people probiotics thrive while others seem to be resistant to colonization.[i] They concluded that not everyone may benefit from standard probiotic treatment. Since we all have different gut bacteria already – as individual as our fingerprints – it only makes sense that people will respond differently.
My thoughts upon looking at the study: it was not long. How do we know that other formulations of probiotics, given for longer periods of time, won’t change the results? As the authors state, “Patterns of colonization resistance upon use of other probiotics strains, or by population subsets not included in our studies, such as children, the elderly and individuals with existing medical conditions merit further prospective human studies.”
In a second study researchers looked at whether or not probiotics colonize the gut after antibiotic use.[ii] There were only 21 people in the treatment group of the study, and these were then randomly divided into 3 groups: 7 people allowed their microbiomes to recover on their own; 8 people were given a probiotic for 4 weeks; the final 6 were treated with fecal microbiota transplant (FMT) which was made up of their own bacteria, cultured before the antibiotics were given. They found, not surprisingly, that antibiotics cleared the way for colonization with the probiotics but – in what naturally stoked the media frenzy – they found that this wasn’t beneficial in that, the probiotics seemed to prevent the microbiome from returning to normal for several months afterwards. (Those treated with FMT returned to normal within days.)
The conclusion, that probiotics may keep the gut bacteria from normalizing following antibiotics, is literally based on results in only 8 people. The authors acknowledge that their study has several “important limitations.” For example, they tested only 1 probiotic product. Before any definitive conclusions can be drawn, many more larger and more robust studies would need to be done.
The first thought that occurred to me when I read about this latter study was “And what about clostridia?” FMT is not approved in the USA for anything other than resistant clostridia infection, so suggesting that doctors harvest people’s microbiota before antibiotics and then do a fecal transplant isn’t happening in this country anytime soon. We are left then – along with most of the rest of the world – with a choice of taking a probiotic or not taking a probiotic when given an antibiotic. If you chose to not take one, do you increase your risk for developing a C.diff infection?
I don’t know the answer and these researchers do not address it at all. However, a very quick search led me straight to a Cochrane review study done just last year that summarized the findings of 39 randomized trials covering a total of 9955 participants. “Thirty-one studies (8672 participants) assessed the effectiveness of probiotics for preventing CDAD [C.diff infection] among participants taking antibiotics. Our results suggest that when probiotics are given with antibiotics the risk of developing CDAD is reduced by 60% on average.” It goes on to say, “Side effects were assessed in 32 studies (8305 participants) and our results suggest that taking probiotics does not increase the risk of developing side effects….The short-term use of probiotics appears to be safe and effective…”[iii]
This then, of course, begs the question, not addressed by this Israeli study: what does the lack of “return to normal” of the gut flora actually mean for human health? Does it actually matter? And/or does it matter enough to forsake the protection afforded by probiotics?
Based on what the data suggest as of today then: I’ll risk it and take probiotics if I need to take an antibiotic…call me crazy.
[i] Zmora, N, et. al. Personalized gut mucosal colonization resistance to empiric probiotics is associated with unique host and microbiome features. Cell. 2018. 174L6):1388-1405.
[ii] Suez, J, et. al. Post-antibiotic gut mucosal microbiome reconstitution is impaired by probiotics and improved by autologous FMT. Cell. 2018. 174(6):1406-1423.