Chris Kresser: Lactulose, I don’t know that you could say it is preferred. I think a lot of clinicians prefer it. Some prefer glucose. But as I mentioned in the SIBO breath testing section, you have to understand the pros and cons of each, and then you have to make a decision based on your sensibility.
With glucose breath testing, you’re going to significantly under-diagnose people with SIBO. You’ll miss a lot of people with SIBO because glucose is absorbed very high up in the small intestine. In the majority of cases of SIBO, the overgrowth occurs in the terminal ileum, which is much further down in the small intestine, close to the colon, so glucose will not catch those people. You’ll get a lot of people with SIBO that are showing with false negative results on their glucose breath test.
With lactulose, you have the other problem. Because lactulose is essentially a marker of transit time and because, as I’ve argued and as we’ve seen in the studies that I shared with you, transit time even in normal individuals can be as little as 70 or 80 minutes, if you see a spike in hydrogen at 90 minutes, the labs will mark that as a positive result with lactulose breath tests, but it isn’t necessarily. It could be, but it also could just be that lactulose has reached the colon earlier in that case and it’s not indicative of SIBO. So with lactulose breath testing, you will over-diagnose people with SIBO.
So the question becomes, do you want to under-diagnose or over-diagnose? In my mind, the next issue is, well, that depends on the treatment. If the treatment is dangerous and risky and has a lot of adverse effects and complications, then I would want to err on the side of under-diagnosing or at least finding a different treatment that wasn’t that way. But in the case of SIBO, both the botanical treatment and the antibiotic treatment are pretty safe as treatments go, and so I would rather, especially if a patient has significant gut symptoms or symptoms that could be related to SIBO, I’d rather give them a therapeutic trial based on an equivocal lactulose breath test and help them than diagnose them negatively and not do anything. That’s especially true given the study that I just mentioned earlier in this call that showed that a lot of people with IBS respond to rifaximin, even if they don’t have a positive lactulose breath test. If that’s true with lactulose, it has to be even more true with glucose since glucose under-diagnoses.
I don’t have anything against Genova. Well, that’s not entirely true. I find their customer service to be pretty bad, but as a lab, the reason I haven’t recommended their breath testing is not because I don’t think their lab testing is valid; it’s that they only offer two hours, and I think we went over why that’s not advantageous and why you can’t really get an accurate breath test result with only a two-hour test. If they brought back a three-hour test, I would certainly consider recommending them again. The other problem is their diet instructions are completely incorrect and not based on anything found in the scientific literature. I have no idea where they came up with their diet instructions and why they changed them to be different, but they don’t exclude all vegetable matter. Basically the patient should just be eating white rice and lean meat the day before the test, and a little bit of oil, and that’s not the instructions they get from Genova, which can be confusing. I mean, you can overcome that by giving them your own instructions, but if you start doing this a lot, you’ll see that having that kind of dissonance between the instructions that are sent with the test and then your own instructions can cause a lot of confusion for patients. Anyway, if they fixed their diet instructions and brought back the three-hour test, I think it would be perfectly fine.