Science Friday - What The Small Intestine Can Tell Us About Gut Health

Episode Date: July 17, 2024

The gut microbiome is an important ecosystem of microbes that lives in each one of us, and its strength affects our overall health.However, the small intestine is an underappreciated part of the gut microbiome. Most of the research into our microbiomes has focused on the other end of the gastrointestinal tract, namely, the colon. And poop samples are an easy way to analyze the microbiome in that lower part of the gut.Better understanding microbiome disruptions in the small intestines may allow researchers to better understand disorders like irritable bowel syndrome, and celiac disease. Dr. Christopher Damman, associate professor of gastroenterology at the University of Washington, gives SciFri producer Kathleen Davis a crash course in the microbiome of the small intestine.Transcripts for each segment will be available after the show airs on sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

Why, better understanding the small intestine might be key to improving gut health. The small intestine is really an almost completely different ecosystem from the large intestine. And you could think of it maybe as disparate as a rainforest in a desert. It's Wednesday, July 17th, and you're listening to Science Friday. I'm SciFri producer Shoshana Bucksbaum. The gut microbiome is an important ecosystem of microbes that live inside of all of us. us, and the strength of our gut microbiome impacts our overall health. And an underappreciated part of this gut microbiome is the small intestine. Most of the research into our microbiomes have

revolved around the other end of the gastrointestinal tract, think colon, and sampling, well, poop. But studying the upper gut may allow researchers to better understand disorders like IBS and celiac disease. Here's sci-fri producer Kathleen Davis, with more. Joining me now to give us a crash course in the microbiome of the small intestine is my guest. Dr. Christopher Damon, Associate Professor of Gastroenterology at the University of Washington, based in Seattle. Welcome to Science Friday. Wonderful to be on, Kathleen. Thanks so much for the invite. It's great to have you. So let's start off with just a quick anatomy refresher. So where is the small intestine located in the general gastrointestinal system?

So the small intestine is actually what connects the upper gut to the lower gut. So in other words, all the way from the stomach down to the colon. And there's several parts to it. There's the very first part, which is the duodenum. That's reachable with an upper endoscopy. And if you ever have one, that would be looked at. After the duodenum, there's the jujunum. That starts to get into the territory.

That's very difficult to get to. And then the ilium. There's the last part of the ilium called the terminal ilium that you can reach by colonoscum. at the very end of it. But a lot of the small intestine, because it is in a spot which is hard to get to, is relatively unexplored. So in layman's terms, the small intestine comes right after the stomach, right? Well put. So what role does the small intestine play in the gastrointestinal system? So the small intestine plays a really important role in at least two elements of our body's physiology. One is it helps us absorb our foods. So all the food that you eat, you know,

you start by chewing it, the saliva and the gastric juices help break it down. But that process of digestion is really completed in the small intestine and the small intestine and then absorbs all of those broken down nutrients. It can help build the cells in your body. So that's one really important function. Another is it actually has tons of immune cells in it. There's actually name for it called the gut associated lymphoid tissue or gault. And that plays a really important role in helping the body distinguish between what is friendly and what is unfriendly in terms of antigens. So a lot of the foods that we eat, a lot of the good microbes in our gut are friendly, and the gut plays a role in helping tell the body that. How is the microbiome of the small

intestines different from, say, the microbiome of the colon? So the small intestine is really a almost completely different ecosystem from the large intestine. And you could think of it maybe as disparate as a rainforest in a desert. And there are certainly analogous organisms that are doing very similar things in the two different parts of the intestine. You could think of it, you know, maybe as a little ground bowl versus a monkey in the rainforest. But, the organisms, the species that are present there are actually quite different. Now, as you get closer to the colon and the small intestine, those organisms start to transition a little bit, especially in the very last part of the ilium, the terminal ilium, and there things start to look a little bit more like

the colon. But the upper gut is very, very different. Can you give just a few examples of the microorganisms in the small intestines that are not maybe further down. in this general GI tract. Yeah, absolutely. So some of the organisms might actually sound a little bit scary or like pathogens. So strep species are very, very common. And we usually think of those in terms of strep throat. But there are healthy strep species too, namely strep salivarius.

And that gets its name because it's present in saliva and actually present in the upper gut as well. There's lactobacilli. And that would be familiar to people because those are often considered. probiotics and they're present in yogurts. But then there's lots of weird exotic sounding bugs as well that people wouldn't recognize. But what unifies these species is they tend to be a little bit more tolerant of oxygen than all of the anaerobes or the oxygen-furing or sensitive bugs down in the colon. Are there disorders that are caused by a dysfunction of this microbiome in the small intestine? Absolutely. And one of the biggest conditions,

that's been associated with the upper intestine, would be irritable bowel syndrome, and that was mentioned at the very beginning. And it's cousin, overlapping cousin, small intestinal bacterial overgrowth. In both these conditions, there's believed to be an imbalance in the microbes that are present in the upper gut,

an imbalance that leads to an overzealous microbial population that breaks down fibers in places where it shouldn't normally. And there's some fibers that are more readily broken down like the so-called FODMAPs. And folks that have these conditions, one of the ways that they often will help treat or address the disorder is by avoiding foods that have these types of fibers in them. Okay. Can you remind me what a FODMap is? Yeah, so it's an acronym. Let me see if I can remember it. So let me see, fermentable oligosaccharides, dye saccharides. monosaccharides, and polyols. Okay. I see why we have the acronym.

How much do scientists actually know about the microbiome of the upper gut versus the lower gut? Is there a discrepancy in what we know? Absolutely. So, you know, we've really focused on the low-hanging fruit, so to speak, and that's the stool that we flush down the toilet every morning and every evening. It's easy to get, and, you know, otherwise it just goes to waste. but researchers love it because they can understand what's happening in the gut. It's a nice proxy for the whole gut, but there is really a limited amount of research looking at the upper gut for the reasons that we're talking about. It's just very difficult to get to. And the upper

gut may be disproportionately involved in things like digestion and our immune system. So it's really a bit of an unexplored frontier still in gastroenterology. Why are the small small intestines harder to study than the colon? I mean, is this just a general problem of it's a lot easier to study poop coming out of us versus getting into our guts to study? Absolutely. So the two biggest ways that we've had for studying the small intestine up until very recently have been in upper endoscopy. And that's something that you'd have if you had heartburn that wasn't controlled by medication that decreases acid in the stomach. And in these very unusual anatomical situations where people have had surgery on their intestines,

and there's a little portal or iliostomy where the small intestine actually empties through the abdominal wall into an iliosomy bag. There's been quite a bit of research about how ultra-processed food alters the gut microbiome. Is this the same for the small intestines? You know, there's very little research that's connected, the small intestine microbiome to ultra-processed foods. Certainly, you know, there are connections there to the lower gut and stool and colonic microbes. But I think this is a very fruitful area for research. And, you know, hypothetically, the nature of ultra-process foods is the balance of a whole food is disrupted. They're concentrated for sugars, for fats.

and a lot of the fibers and other nutrients, so-called phytochemicals that are present in plants like polyphenols are removed. And both fibers and polyphenols probably play an important role in shaping, not just the colon bugs, but the bugs that are in the small intestine. But I think future research, this is a very ripe area for discovery. So we've talked about how hard it is to actually study the small intestines. Is there an opportunity for new technology to advance this research? 100%. And there's actually some new technology that's come out in recent years. And for a while now, we've had clinical tools that just take pictures of the small intestine. And they help diagnose things like little blood vessels that can bleed and lead to anemia in people. But very recently,

there are at least a couple new technologies or classes of technologies that allow us to look at the small intestine, not just by looking at it, but also sampling, you know, taking bits of the juices that are present there so that we can look at the microbes and all of the metabolites that they're producing. And one of those is a little pill that has a trapdoor and a compartment, and it's triggered to open up for different pHs along the gut tract. And so it can sample different parts of the small intestine. And that's going to be a game changer moving forward using that. technology in the context of different diet studies. So we can understand how the small intestine is being impacted too. But there's another technology which, you know, unlike a upper endoscopy,

which is about the size of my pinky in diameter, very, very thin filament, almost the size of an angel hair pasta that goes through the nose and is minimally invasive, doesn't require sedating medications and provides a portal to the small intestine. So I think a combination of these technologies will be pivotal for understanding, charting, characterizing the small intestine. So in addition to being a researcher, you also are a physician, you see patients. How close are we to a time where a patient can walk in your door and you can give them a targeted treatment based on the microbiome of their small intestines? So I love this idea. And there's been a lot of talk of personalized medicine and personalized nutrition. And,

being able to characterize the microbiome and say, this is a prescription for food specifically tailored to you. There's actually some companies that are making forays into this, early fours, largely around blood glucose control and diabetes. But, you know, the reality of this is, in general practice, we're probably a little ways off still of this becoming a reality. And I'd say in the meantime, it really goes back to a very simple adage. of eating, you know, a whole food diet. And the advice that you've received from your doctor from the beginning, which is to eat nuts, seeds, beans, fruits, vegetables, whole grains, you know, things that are present in well-studied diets like the Mediterranean diet or the DASH diet.

That's about all the time that we have for now. I'd like to thank my guest, Dr. Christopher Damon, Associate Professor of Gastroenterology at the University of Washington. He's based in Seattle. Thanks so much for joining us today. It's been a pleasure. Thank you, Kathleen. That's about all the time we have for today. Lots of folks help make the show, including... Felice Amirs. Danielle Johnson.

F. Rami. Tomorrow, what's it driving widespread drug shortages in the U.S.? And where do we go from here? I'm sci-fri producer Shoshana Buxbaum. Catch you next time. Thanks for listening.