In this ~10‑minute educational video, Dr. A explains the intricate, multi‑stage process that moves food from the moment we desire it to its arrival in the colon. He frames digestion as an orchestra, where mechanical actions (chewing, stomach churning, intestinal peristalsis) and chemical actions (acid, enzymes, bile, bicarbonate) must be precisely coordinated. The stomach acts like a cement‑truck, mixing food with acid to begin macronutrient breakdown. As chyme enters the duodenum, pancreatic and biliary bicarbonate neutralize the acid, preventing duodenal ulcers and enabling enzymes to function. The small intestine then uses segmental squeezing (peristalsis) and a long absorptive surface to extract nutrients, with distinct regions handling carbs, fats, and proteins. Each gut segment hosts its own microbiome; disruption of motility can cause SIBO/SIFO, while an overactive fight‑or‑flight state impairs autonomic regulation, leading to reflux, bloating, and poor digestion. Dr. A also touches on food sensitivities that may be hidden and the importance of prebiotic foods to support a healthy microbiome. He concludes by noting that any imbalance in this orchestrated system can cascade into broader immune and inflammatory issues, promising a follow‑up video on absorption.
Chapters
Hey, it's Dr. A. I wanted to answer a really common question. We're going to do it in a couple of parts because I'm trying to keep these shorter videos down around the 9, 10, 11, 12 minute mark. We'll see how that goes, but these are a little easier to access than some of the hour-long ones unless you're on a drive or a long walk or a run or something. So the first part of this is talking about our digestive system health And food and really what happens when, when you eat. Now, you're going to say, well, I've been eating my whole life, I've kind of figured that out. But from a health point of view, from a medical point of view, there's a lot of things that go on between the part of first seeing, desiring food, smelling it, all that stuff, to getting it in, chewing it, getting it all the way down through your digestive tract, and then having it actually broken down as we go through. Now, I want to focus in this one on the actual aspects of getting the food through you, if you will, and all of the orchestration that's required in order to digest your food appropriately. We'll have another probably 10-minute one where we talk about what happens when we do get it to that point of digestion. But the first thing is, and this is a big reason why you can develop certain types of chronic gastrointestinal illnesses, the first thing that can go wrong is we can confuse a very, very complex orchestrated system. So if you think about it, you have— and I use the word orchestrated because it literally is like all of the, you know, all of the constituents of an orchestra and a conductor, etc. So it's not just Yeah. It's not one thing, you know, where you're looking and you are only getting music out of the trombones or something like that. It's everybody. And just like in an orchestra, they raise one group and lower another group, and then pretty soon they're doing the opposite, and pretty soon everybody's playing, then pretty soon just the flutes are playing. That's exactly how your digestion works. So you can imagine that if all of that has to go on in order for you to get the food in, to get to the point we're talking about in the next visit, of digesting and absorbing and getting the nutrients out of it, a lot of things could go wrong in there. So the first thing to think about is you chew your food and you swallow it. Of course, we're all very familiar with that. That's really the last conscious part of digestion that you have. After you swallow it, it goes to your stomach, okay, down through your esophagus to the stomach. Stomach has a very specific phase that it does, and I've used this analogy before. The stomach is sort of like a cement truck. It's It's sort of an oblique kind of a sheet, a C-shape, and it actually tumbles the food around, okay, just like in cement inside of a cement truck. Now, while it's doing that, it's adding acid in, and acid has certain components that break down certain parts of your macronutrients that you've eaten to try and break them down into smaller pieces. More on that later. You can't have that acid though because the pH of, of that gets very acidic, which is great for the stomach because it's set up for that biologically. But then you put it into the first part of the small intestine called the duodenum. If it stays acid in there, you will burn a hole in your duodenum, and they call that duodenal ulcer. That's one of the first things that can go wrong. Well, how does it know to neutralize that pH? Well, As the stomach is doing its job, it sends then the mixed food down into the duodenum, but it sends some hormonal and partial neurological signals that tell other organs to secrete bicarbonate in. Yeah, just like bicarbonate of soda that you have in your kitchen, only it's a human biological bicarbonate, and it comes from a couple of different sources, but the 2 main places— big place is the pancreas, but you actually make a little bit from your— Liver. your bile tract as well. So then those 2 guys get involved, pancreas producing enzymes and some bicarbonate, and the gallbladder releasing bile for fat emulsion. And as I said, a little bit, a little bit of pH altering stuff in there too. And so this nasty acidic stuff that would burn a hole normally in your duodenum is neutralized. Well, now the pH changes. And then the enzymes in the bile can go to work on the next phase. That's the small intestine phase where it starts. So you have this first part of your small intestine, the duodenum, is very important because it plugs into connectors from your pancreas for enzymes and a bunch of other digestive juices, they like to call them, and then the bile from your liver, gallbladder, and then into there as well. Then in the small intestine, you have a lot longer small intestinal— we've seen pictures, it's like a The hose, and it works to break your food down further through chemical means that we talked about, things like enzymes and the bile, etc. It has some hormonal activities going on, and a big one is mechanical mixing motility. And instead of the big cement mixer thing like your stomach does, the small intestine actually squeezes down one piece at a time. So when this piece is squeezing down, this one is relaxed, and the food moves forward. The chyme— it's sort of like baby food at this point— moves forward, and then this part of the small intestine keeps it for a while and absorbs, digests, etc., and then that squeezes down, and the one after it opens up. So it literally is sort of squeezing one little link at a time. This gives you a lot of time and exposure to your very long small intestine, So you absorb all of those wonderful things. Now, while that's happening, there's a lot of feedback that goes on, even up to your brain. You're not thinking about it, really, unless your stomach hurts, but there's a lot of local feedback neurologically and hormonally. There's a huge amount of hormonal things involved in digesting your food, moving it through. Now, another thing that happens as it goes through Is in the small intestine, uh, there's fluid with it, some of the fluid that you've obviously drank, but also fluid that comes from the cells inside your small intestine. And so what you hydrate in the small intestine as it goes through is a very good thing, and then later in the small intestine and the colon, you take a lot of that water out because you, you need the water to absorb the nutrients, but As you've probably experienced, if you have too much water, when it gets down to your colon and you're going to relieve your bowels, you'll have watery stools, diarrhea, etc. That's where they come from. So each part of the small intestine, there's 3 divisions. Each part does a different job of digesting absorption. Again, we'll talk about that later. And there's a lot of recycling. So the bile acids that go in, and the bile salt, bile acids, depending on where they're at, They get recycled at the end of the small intestine back in, so your liver can actually reuse them. There's different places where you absorb more, you know, carbohydrate or fat, proteins and amino acids. Again, everybody has a job. Now, the next thing is that there's a biome, the good bugs we like to call it, and each section has its own different biome. So your mouth, your oropharynx, has one set of biome. Stomach has a totally different one. It's very acid tolerant, obviously. The duodenum, and then the jejunum, the next one, and the ileum, different biome. And then your colon has a whole other biome. So another thing that can happen is a bacterial overgrowth that goes on if this motility that's happening is not happening appropriately. There's a lot of reasons for that. People get SIBO or SIFO, small intestinal bacterial or small intestinal fungal overgrowth, simply because you're not getting the sweeping motion of the food moving through and getting digested, and so you can actually get the wrong bacteria in the wrong place. That causes a lot of digestive upset symptoms. But the other thing that can happen is more of a garden variety thing is because the neurological system has to switch over the autonomic nervous system, automatic part, you go from fight or flight to resting and digesting and all of that. If you're not in the resting and digesting area and you're always on fight or flight, you're always eating on the run, all that stuff, you can actually develop a lot of indigestion simply because the neurological symbols Symbols. Or signals and symbols are not going to move through your system appropriately. And so if you're in fight-or-flight mode or angry or working or whatever else and you're not resting while you're eating, your digestive capacity goes down. You can get a lot of reflux, like heartburn. You can get bloating and gas. You get a lot of other dyspeptic sort of symptoms. And the other problem is that you won't digest the food. It'll still move through, but it may create a lot of gas later on because you have all these partially digested macronutrients that aren't supposed to be partially digested. So there's a lot of different things that can get thrown off. One of them is the balance between your autonomic nervous system, so being resting and calm enough to eat and digest appropriately, The bacteria and other microbes that are supposed to be in the different phases of your digestion, if they get thrown off, that throws off everything. They're terribly critical for both being there and maintaining your digestive health, but also for helping you digest and helping your digestive immune system. So the next thing is, if we mess up a lot of these other things and we're not digesting well and the microbiome goes out, we actually can throw off the digestive immune system, which is a huge part of your immune system, and then that can open the door to chronic infectious things and dysbiosis, where the bugs are out of balance, and all kinds of, you know, things that can go everywhere from just making you feel not great when you eat or between meals, all the way to opening the door for chronic, you know, infectious or inflammatory process. The other thing that can happen is if you're eating things that your body just isn't appreciating, foods that it's sensitive to, allergic to, etc., you may not notice it. And I've had this discussion a lot with patients where they'll say, well, gosh, I don't feel bad when I eat, you know, that food. And you take the food away for, you know, 4, 6, 8 weeks, they eat it again, and suddenly they feel bad. Well, it's because they were eating it almost every day or every day. So your body downregulates those sensitivity or allergy problems that come on. Now, the other thing is just what you're eating. Now, that's a topic for a whole other day as well, but one of the things to consider is there's a lot of foods that are called prebiotic. You've heard of probiotics, you take a pill with, you know, good gut bugs in it. Prebiotic foods you can just work into your diet. You can go online, There'll be, you know, 2,000 websites with prebiotic food ideas, and you may not like all of them, but there's a lot of them. So you keep those in your diet, you'll notice that they're in a lot of, you know, indigenous diets, which is why people stay healthy usually in those. Getting prebiotic foods in can be very good too, a good way to do that. Well, we've talked probably enough about that. You can see how many players there are in the game, and when you have both hormonal and mechanical and neurological feedback going on to a system that's this long and with this many parts. If you get it out of sequence or you get it out of balance in one way, everything else can start to shift and go out of balance. All right, well, that's enough for this one. We're going to pick up on digesting and absorbing in another one of these that we do, but I'm Dr. A. And this is Health Questions with Dr. A. So like, share, subscribe, please do all of those things if you want, and I will see you next time. Bye.
