 Hey everybody, Dr. O. In this video, we're going to talk about the three phases of digestion. We're going to start here with what's called the cephalic phase. What I find most interesting about this is you see, obviously eating food, tasting food, smelling food, even seeing or thinking about food can stimulate the cephalic phase. That's why it's called cephalic, the brain phase of digestion. So smelling food, hearing food, sizzle, seeing food you really like, thinking about food will actually stimulate the secretion of the cells in your stomach, so that your stomach is basically preparing for digestion before you've ever taken a bite. Now there are things that can turn this off as well. This would be why some people would lose their appetite if they're depressed. Let's say you're sick, you have an upset stomach, you might smell your favorite food, but it's probably not going to trigger the same response because you don't have an appetite. So those are the types of things that can actually decrease the cephalic phase. But what I find the most interesting about this and the most important is that a digestion begins when you think about food, when you sit down at a restaurant, when you order food, you're seeing food, you're smelling food. Digestion has technically already begun, at least preparation for digestion has already begun. So that's called the cephalic phase of digestion. Then we have the gastric phase of digestion. So obviously as your stomach fills up and the pH is going to start to rise because you're adding all this stuff, water and everything else, the stomach can sense that it's filling up with food and that's going to lead to the increase secretion of digestive enzymes and acid because now the stomach's in charge. It knows, that's what's called the gastric phase. It knows that there's now food sitting in there and it has to be digested and that's going to cause this increase in digestive activity. Now I want you to note here on the bottom though that too much stomach acid can be initial but there's lots of other things that can actually inhibit stomach digestion. Now I don't think this is a huge deal with the stomach for most people but on the flip side, if you have too high of a pH because you're taking acid-lowering medication so I know the treatment for heartburn is acid-lowering medication but here's an issue with that. If you're constantly raising the pH of your stomach by blocking acid production or basically neutralizing the acids in your stomach, that higher pH can cause some issues. It basically can tell your intestines, it can limit how much the stomach can tell your intestines about preparing for digestion. So what I would say here is, of course if you have heartburn you have to get a dealt with but the answer is in years and years of lowering your stomach acid. You need stomach acid so I won't go into great detail here but one thing I do want you to note is that if you have too high of a pH in your stomach that impacts the digestion and absorption of all three of your macronutrients. You might think if my stomach pH is too high that's going to impair my ability to digest proteins because the job of stomach acid is to denate your proteins but because of its impact on hormones and other chemical messengers that speak to the rest of your GI tract, too high of a pH will impact the digestion and absorption of all of them. Imagine a real high pH stomach with not enough acid is going to tell the pancreas. Well there's no reason to make a bunch of digestive enzymes and secrete them. It's also going to tell the liver and gallbladder. We're not going to need a lot of bile. There's nothing going on here. So just something to note, again I try to add clinical pearls whenever possible. Lastly we have the intestinal phase. So as food first starts to join the intestines, your body is going to say okay let's empty the stomach, let's move this food into the intestines. But the presence of food there is going to shut off that movement. So the reason you're not hungry after just eating is your stomach is full, your stomach is now filling your intestines so you shouldn't be hungry for at least a couple of hours minimum after a meal because the presence of all that food, the presence of a stretched out duodenum is telling the stomach we don't have any more room, don't be sending anything our way. But then of course once the intestines clears out and once the stomach clears out and everything is empty again, you'll be hungry again and that sight or smelling or tasting or eating food will start this process all over. So that's the three phases of digestion, the cephalic, gastric and intestinal phase. Hope this helps. Have a wonderful day. Be blessed.