Chris Kresser: I want to start by talking a little bit about SIBO and breath testing. This was a question sent in by Angela originally that I had mentioned I would get back to her on. I talked about in the SIBO treatment section that there was an Italian study looking at radioisotope tag of lactulose in transit time that showed that lactulose can hit the colon a lot earlier than the breath testing criteria seem to assume and than many clinicians and researchers assume. I actually just posted something to the ADAPT Facebook group about this, so if you want to get a link to the actual study and some excerpts from that study, you can go check it out there, but I’m just going to go over a few of the key points.
This was a new study. They didn’t actually do any measurements, but it’s the best one-stop-shop review of the previous research looking at lactulose breath testing as a measure of orocecal transit time. It’s important to understand that that’s actually why lactulose breath testing was developed. It wasn’t originally developed as a test for SIBO. It was developed as a test to measure transit time and then only later became adopted as a SIBO breath test because of the problems related to small bowel aspiration. It’s just an unwieldy test that’s not very patient friendly, and it’s invasive, and there are all the problems that we talked about in the SIBO unit.
A couple of the salient points from this review: They were talking about previously conducted research where they did simultaneous hydrogen breath testing and scintigraphic studies of isotope-labeled lactulose, and they found that the average arrival time of lactulose in the cecum, which is the colon, was 73 minutes and that individual arrival times ranged from 30 to 140 minutes. That tells us there’s a huge individual variation in orocecal transit time, which is problematic because we don’t know that when we do a breath test on a patient. We don’t know what their transit time is, and to a certain extent, that’s the whole point of this test.
The other thing is that the average transit time was 73 minutes. That means half the people … or a smaller number of people … it’s not the median, but less people had transit time that was actually less than 73 minutes, and some people, of course, had transit time that was more, but it means that for the most part, if we just talk about it on average, the lactulose is getting to the colon at 73, which is well before the 120-minute cutoff that QuinTron uses as criteria for a positive result on a SIBO breath test. If you see, for example, a single lactulose peak, and the peak starts at 90 minutes or 100 minutes, most of the labs are going to mark that as positive, but we don’t really know that that’s positive because especially if it’s a single peak and if the lactulose is arriving, on average, at 73 minutes, then how do we know, in that case, that lactulose isn’t just getting to the colon and that’s what’s causing that peak?
Along the same lines, a total of almost 70 percent of patients had arrival times that were less than 90 minutes by both hydrogen breath test and scintigraphy. That, again, suggests that not just some patients, but the majority of patients we measure, the lactulose is getting to their colon before 90 minutes.
There was another study that they talked about with patients with IBS who received isotope-labeled lactulose, and their cecal arrival times ranged from 10 minutes on the low end, which is just super fast, and that’s obviously someone who has diarrhea and really fast transit time, to 220 minutes on the long end, so that’s probably someone who’s severely constipated. But again, the average was 71 minutes, very close to the 73 minutes in the previous study.
Another consideration is that lactulose is a laxative, so it actually accelerates small bowel intestinal transit time. We’re giving someone a laxative on an empty stomach, and then we’re measuring the progress of that laxative through the intestine, and of course, that’s going to cast some further doubt on the accuracy of breath testing because even if someone has normal transit time, then they take the lactulose, it gets faster, and let’s say you see a single hydrogen peak at 65 minutes. How do we know that that’s a positive result?
I think the takeaway from this is not that breath testing is completely useless, but that it is problematic, and it’s not as straightforward as the consensus view has made it out to be. You really have to consider this data if you’re using this kind of testing in your practice and look at the test results with a skeptical eye and also not just follow the criteria that QuinTron and the other labs are using to determine whether these tests are positive or negative. For example, I just saw a result come in yesterday for a patient, and both hydrogen and methane were very low until about 85 or 90 minutes, when they started to gradually increase. It was just a single peak, and it went up starting at 80 minutes, 85 minutes. This was with NCNM, and they marked that test as a positive result because that’s their criteria. There was an increase of over 20 parts per million of hydrogen from the lowest preceding value before 120 minutes. But if we take into consideration everything that we’ve just been talking about so far, that’s not enough information, in my mind, to say that that patient has SIBO.
This study actually suggested new criteria, which were a double peak, so they’re using the original criteria that were proposed for SIBO breath testing, not the later, more lenient criteria, of having a double peak, but they’re actually making it even more strict than the original double-peak criteria. They are suggesting that the first peak should happen within the first 60 to 80 minutes because, as they argued, average orocecal transit time is somewhere between 70 and 73 minutes, and 70 percent of patients had arrival times that were less than 90 minutes. So they argued that if you use, like, the first peak occurring before 80 minutes, that’s going to be a lot more specific for SIBO.
I think this is pretty murky, and we desperately need a better diagnostic tool for SIBO. The clinical consequences of this are that if you see patients that continually are testing positive with these late hydrogen peaks and you’re focusing all your energy and attention on treating SIBO, the risk there is that you’re ignoring other potential causes of their symptoms and you’re not actually going to make the progress that both you and the patient would like to make. I’ve seen this happen also with patients, where they get totally obsessed with the idea that they have SIBO and recalcitrant SIBO, and they go to herculean lengths to prevent SIBO recurrence, and they’re on extreme low-FODMAP diets for long periods of time, which have potential consequences that we’ve talked about, and they’re basing that almost entirely on this very lenient criteria for SIBO breath testing that has never really been validated clinically and really can’t be because there’s no gold standard test to validate those breath test results against.
It’s a mess, to be frank, and as clinicians who want to just help our patients, I think the takeaway here is, yes, we can use lactulose breath testing, but it needs to be used with a big grain of salt, and we need to be thinking about these factors as we interpret the results, and we need to also consider individual transit time in our patients and other things that we talked about in the curriculum itself to determine whether SIBO is really present.
OK, I know that took a good chunk of time, but I think it’s really important to cover because I know some people will probably disagree with this, but I think SIBO has become a little bit of a fad diagnosis. I can tell you, having done hundreds of these tests now, it’s pretty rare that we see a negative result, and that alone tells me something. I don’t believe that every single person has SIBO. I don’t think that the research supports that, and generally, I think, we should be wary as clinicians to see any test that always returns positive results. There may be some exceptions there, but in general, that should always raise your eyebrows, in my opinion.