Dr. Amy Nett: PHGG and soluble fiber. There’s certainly been some research that PHGG does increase the levels of beneficial bacteria like Bifidobacterium and Lactobacillus, so to some extent, it does seem to preferentially increase the numbers of beneficial bacteria, but I don’t think it’s selective. There’s still a lot we’re learning, and that’s one of the reasons why we tend to recommend a variety of prebiotics. The more variety in prebiotics you can bring in, I think it’s probably better, and I think we need more research to know for sure.
Similarly, does sugar in our diet feed the pathogenic bacteria? Well, it probably doesn’t selectively feed the pathogenic bacteria, but at the same time, if someone has a high-sugar diet, I’m guessing that looks a little bit more like a Standard American Diet, and it’s probably more what’s lacking in the diet that’s leading to dysbiosis. So if it’s a high-sugar diet, it’s probably a low-broccoli, low-kale diet as well, or a low-onion and low-resistant-starch kind of diet.
I think the more variety in terms of prebiotics and those healthy types of fiber that you’re getting in there, like the various types of soluble fiber. You mentioned PHGG, but remember there’s also larch arabinogalactan, inulin, and fructooligosaccharide. I think it does feed some of the pathogenic organisms, as well. The reason I think that is because when you give a patient who has SIBO or dysbiosis soluble fiber, when they have low levels of beneficial bacteria and a lot of pathogens, they have pretty bad reactions. So I think it’s probably reasonable to think that those fibers do feed both beneficial and pathogenic bacteria, but it seems that there’s overall more benefit in terms of selectively feeding or nourishing the beneficial strains. More research needs to be done, I think. And remember, too, when someone is feeling like they’re developing a SIBO recurrence, I think about doing a low-FODMAP diet or one low in microbial-accessible carbohydrates, the carbohydrates that we’re not fermenting, that they’re getting, because you want to starve out the bad bacteria.