You guys love the microbiome.  You're not alone.  The sales of products containing yeasts and bacteria that'll colonize your gut and make you stronger and better are legion.  At a recent trip to the NIH,   met a researcher who did actual microbiome work and he didn't seem nearly as convinced as all of you do, but do probiotics work?  That's the topic of this week's Healthcare Triage.

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When I was a kid, back when there were like, five channels on TV and yes, five, it was a nightmare, I remember once watching this show on PBS, which was one of those five channels.  You people have no idea what it was like.  This show used newfangled high powered microscopy to show the strange and frightening creatures that lived on and in our bodies.  I was horrified.  This is what passed for entertainment in the late 70s and early 80s.

We now know that these bacteria, yeasts, et cetera are an important part of our health.  One way they help is by taking up space and preventing other bad germs from colonizing or infecting us.  That's one of the reasons people can develop yeast infections or (?~1:08) infections after taking antibiotics.  You killed the good stuff and the bad stuff moved into your vacant guts.

Probiotics are supposed to help you get more good stuff.  You buy and eat yogurts with live cultures or supplements containing the same and they see your gut and move on in.  So this sounds sane, but it also sounds simplistic.  It's not like everyone has the same microbiome, and it's not like your microbiome is always the same.  After all, people take antibiotics all the time.  They're killing off then changing what lives inside their guts all the time.  It's not like people don't benefit from antibiotics.

Less theory, more evidence.  To the research!  The most obvious area probiotics can make a difference given that we're consuming them orally, is in the gut.  If we know that antibiotics can cause diarrhea, maybe probiotics could prevent it.  There's a systematic review for that.  

JAMA, 2012, "Probiotics for the prevention and treatment of antibiotic associated diarrhea".  Researchers reviewed 82 randomized controlled trials.  Most used lactobacillus, alone or in combination with other cultures.  They managed to get 63 of those trials containing almost 12,000 participants into a meta-analysis.  They found that using probiotics reduced the risk of antibiotic associated diarrhea by 7% and that's not absolute difference, not relative, so the NNT was like 13, and that's pretty good, but that's a really specific kind of diarrhea.  What about regular old infectious diarrhea?  There's a systematic review for that.  

Cochran, 2010, "Probiotics for treating acute infectious diarrhea".  They found 63 studies with more than 8,000 participants.  Most of them looked at infants and kids.  They also found a difference of about one day less of symptoms overall.  They also found it reduced the number of stools had on day 2 and the likelihood of diarrhea lasting at least four days.  

Let's acknowledge that the risks are low in using probiotics.  They're usually not expensive, either, so if you're looking to treat diarrhea, they seem like a pretty good option, but what about constipation?  Well, time to ratchet back the excitement a bit.  There's a systematic review from 2010, but it could only find five trials with fewer than 400 subjects and they weren't very impressed with the results.

There have been some more recent studies but again, we're talking about outcomes like improved constipation after weeks, so it's not like you should use it for your bout of acute constipation.  So what do we have?  Pretty good evidence to use probiotics for antibiotic associated diarrhea and acute infectious diarrhea and, eh, evidence to use them for chronic constipation. 

The problem, as always, is that you want to use probiotics for everything.  There are Cochran entries for the use of probiotics for hepatic encephalopathy, ulcerative colitis, food allergies, bacterial vaginosis, Crohn's disease, upper respiratory airway infections, eczema, gestational diabetes, and even pre-term labor.  If there are Cochran reviews, that means that there have been more than one study on each of those things, and the results are that there's no good data to support probiotics for almost any of those issues.  That hasn't stopped many of you from giving them a go anyway.

Part of the problem with all the research though is that all probiotics are not the same.  As I said, there are many different beasties that fall under the probiotic rubric, and they're not all similar.  Some get good results, some don't.  Some studies aren't even good at reporting what they used.  Further, a lot of probiotics are considered supplements and they aren't regulated.  You can't be sure what you're getting, even if the stuff is alive in yogurt, studies show that doesn't necessarily mean that they get to your gut alive.

For instance, recently, there's been a big push to use probiotics to treat infantile colic.  Some trials found that they made a difference, but those trials were inconsistent in their methods, so a group of researchers performed a better, more generalizable trial and published their findings last year.  They found no significant difference between those who used probiotics and those who didn't.  

The larger question here, though, is what are we doing?  Why do we think that we're so screwed up in what we eat that we need to start manipulating the microbiome and what's living inside of us?  It makes total sense to me to try and fix problems we caused with the use of antibiotics or caused by other germs through infections causing diarrhea, but when we start calling other things disease, well, we've got an episode for that.

Similarly, when we start calling food, medicine, and using it to treat stuff, we wind up going beyond its mandate.  Dr. Billy Bennett, one of my IU colleagues, called probiotics and I'm quoting, "A hammer in search of a nail" in an editorial on that colic study in the BMJ.  He also cited Dr. Beth (?~5:47)'s work, which we featured before.  Beth was my resident back in UW.  Healthcare Triage has its fingers in everything.

Healthcare Triage is supported in part by viewers like you through Patreon.com, a service that allows you to support the show through a monthly donation.  Your support helps us make this bigger and better.  We'd especially like to thank our research associate Cameron Alexaner and our first ever surgeon admiral, Sam.  Thanks Cameron, thanks Sam.  More information can be found at patreon.com/healthcaretriage.  

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