This is a longer cut than I usually like to take, but for those who deal with this issue, it is very informative. Point one - FODMAPs and gluten overlap to create IBS symptoms. Two - human science is hard to do well. Three - can you believe folks are actually testing this kind of thing, finally?
So the first one was a study about the gluten-free diet and how it improves irritable bowel syndrome, diarrhea-predominant irritable bowel syndrome. There are two different types of irritable bowel syndrome. There’s constipation predominant and diarrhea predominant. In this study, they took a bunch of people with diarrhea-predominant IBS, and they didn’t select them on the basis of prior self-reported gluten intolerance, which is good because some studies have done that and it kind of biases the results. So it was just a random sample of patients with diarrhea-predominant IBS, and they put them on a gluten-free diet. And they found that the people who followed a gluten-free diet had decreased stool frequency, so their diarrhea improved. And they also had less gut permeability, so their guts weren’t as leaky. And they had increased expression of tight-junction proteins that regulate the intestinal barrier, so again that’s another way of saying that the gut barrier integrity improved. And these effects were greater in people with the HLA-DQ2 and DQ8, which is the genotype that is associated with gluten intolerance and celiac disease. That’s not the first study that showed that, but it was another study that showed that a gluten-free diet can improve IBS.
This other study, though, showed that a gluten-free diet, while it does help with IBS, it doesn’t help IBS patients that are already on a low-FODMAP diet. They took a bunch of patients, put them on a low-FODMAP diet, which we’ve talked about before. FODMAP stands for “Fermentable Oligosaccharide, Disaccharide, Monosaccharide, And Polyols,” and they’re basically specific types of carbohydrates or sugars that are not well absorbed in the digestive tract, and then they can linger around and become food for pathogenic gut bacteria, and if SIBO is present, small intestine bacterial overgrowth, which is one of the causes of FODMAP intolerance, eating a lot of FODMAPs can make it worse, and then studies have shown that removing or greatly restricting FODMAP intake can have a profound effect on IBS. In fact, I think some studies have shown up to 75% to 80% of patients improve, which is way, way better than any drug treatment for IBS.
So they were randomly assigned to groups, and they were all on a low-FODMAP diet. But then there was one group that was placed on a high-gluten diet with 16 grams of gluten per day. And there was another group that was on a low-gluten diet, and that was 2 grams of gluten per day and 14 grams of whey protein a day. And then there was another group on a control diet with 16 grams of whey protein a day. And then they assessed different markers of intestinal inflammation and immune activation and then different ways of measuring fatigue. And this was a crossover study, so 22 of the patients then crossed over and ended up in a different group, so the patients that were on the low-gluten group went into the high-gluten group and vice versa. And that’s a good way of doing a study like this. It just strengthens the results. If you find, for example, that patients in each case that were on the low-gluten diet did better rather than just one group of patients, it strengthens the results.
As suspected, the low-FODMAP diet universally reduced symptoms in everybody, regardless of whether they were eating gluten or not eating gluten. But reintroducing gluten once FODMAPs were already really restricted didn’t cause any problems in this particular study group. So there was no difference in symptoms in people on a low-FODMAP diet who were taking supplemental gluten and people that were on a low-FODMAP diet and weren’t taking gluten.
This is certainly interesting. I mean, does this mean that we should eat gluten? I don’t think so – you may not be surprised to hear me say that – for a few reasons: Number one, these results actually directly contradict a previous study that the same researchers did. It was a placebo-controlled study where they gave patients capsules, some with gluten and some with a placebo powder that didn’t have any gluten in it. And these patients were also already on a fairly low-FODMAP diet, and they did that to kind of reduce any background noise because these researchers knew that FODMAPs can trigger or exacerbate IBS symptoms. And in that study, the patients who did receive gluten had more symptoms and were worse off than the patients who didn’t. So there are two completely different results there.
Steve Wright: I haven’t seen this study, but do you think that in this new study they just measured the wrong variables or they measured the wrong things?
Chris Kresser: I don’t know. I mean, one thing that’s interesting is that they used whey as a control. And certainly some patients with IBS would be sensitive to whey, in my experience.