Understand the Three Phases of Digestion_Final

>> Hi there. Are you ready to officially get started on your journey through gut health? In this lecture, we're going to start right off by talking about the three phases of digestion. This covers everything that happens from the time you put food in your mouth until it comes out the other end. Something I discovered when I began to really understand this entire process was the more I knew, the more I considered what I put in my mouth. Let's see if you feel the same way too. Think of your favorite dish or food, imagine that someone is cooking that dish right now in the kitchen just for you. What is it? Is your mouth watering? Have you ever noticed that just the thought of food, especially something you really like can make you start to salivate? For me, it's the thought of roasted sweet potatoes. That's because the very first step of the digestion process is a mixture of conditioned and unconditioned responses, as your salivary glands excitedly prepared for the food that's coming. Your mouth is your first digestive organ, and the digestive process continues all the way through the esophagus, the stomach, the small intestine, and the large intestine, until it comes out the other end, the anus. Yes, we'll talk about the anus and poop in this course. The Greeks thought that if digestion were impaired, the rest of the body would suffer. Yet, in the Renaissance, digestive organs were believed to be void of spirituality and even sinful because they were viewed as unclean. Beliefs and feelings about the gut go in and out of favor, but no one can argue that their function isn't essential. And I dare to say, it's a beautiful orchestration of many organs, hormones, and neurons. So why do we need to digest food? Why do we evolve into beings that chew, break food down into multi-stage process rather than a snake that swallows a mouse whole? Eating can be enjoyable and fun, but beyond that, why do we really need to do it? And what have we learned about digestion through the years? When we look at our digestion, we're not actually all that different from apes in this respect. Perhaps our colon is slightly shorter, but did you also know that the colon varies in length from person to person? Galen, an ancient Greek physician, believed the length of the colon was the sign of being a higher being. Not sure what that says about us compared to apes, even if we aren't sure how we evolved, digestion has been the key to our evolution, survival, and growth. It keeps us alive, gives us energy, provides the raw materials we need to rebuild our cells, our tissues from fueling the healing process when you cut your finger to rebuilding muscle after you've torn it down at the gym. Even when cells die off and they need new DNA, digestive food provides the fuel to build that too. The main job of digestion is to break down food materials into particles small enough that our body can utilize them. This means breaking food down so that we can access the energy known as calories, stored inside fats, proteins, and carbs. Here's some food for thought. To improve our relationship with food, what if we started thinking of calories as energy stored inside a ripe seed, for example, rather than something to avoid? Okay, so taking this further, fats, proteins, and carbs need to be broken down into water-soluble nutrients that can be absorbed through the intestinal wall. Think of how small our cells are compared to a burger. Our digestion has its work cut out for it. We often use words gut, intestines, and stomach, interchangeably to describe where we digest food. But truly, our digestion runs through a long hallow tube and hallow organs that essentially take in food, well, hopefully food, we know there's a lot of non-food ingredients in people's diets these days. And as the food travels down this tube, it's broken down into its smallest form called monomers, which is just a scientific name for a molecule that can bond to another molecule and form a chain. To keep it simple, fats, proteins, and carbs are polymers, a chain of molecules. Our digestion breaks down these polymers or chains so they can be absorbed into the intestinal lining to build new chains. Monomers are the perfect building materials. To recap, the goal of digestion is to break down polymers into monomers so the body can build its own polymers. Now that's a tongue twister. Now back to the digestive tube that runs from the mouth to the anus. This tube is called our alimentary canal. We assume that our alimentary canal is inside the body because we can't see it, but it's technically outside of your body. Did you know that? Your digestive tube is exposed to the outside world, meaning not only can food enter but so can anything else. That's why our tubes are coated with epithelial cells, which are cells that serve as a barrier for every part of our body exposed to the outside world. The entire digestive process takes anywhere from 24 to 72 hours. This varies from person to person, some people are slow digesters and others are fast. There are no medals to be won for fast digestion, and don't worry, it doesn't matter much at all unless either becomes extreme. We all know what that looks like. The different rates in digestion can sometimes depend on the food we eat and whether we're stressed or calm. And it does seem that some people have longer colons than others. Now let's zoom in a little closer and examine the three phases of digestion. One, the cephalic phase or the oral phase. Two, the gastric phase. Three, the intestinal phase. Phase one, the cephalic phase and also called the oral phase includes the mouth, the esophagus, and the pharynx. As mentioned, the thought, smell, or taste of food sends a signal to the salivary glands which prepare the food for transit down the esophagus. This preparation requires a lot of chomping and chewing because remember the goal is to break the food down into little bits or monomers eventually. As we learnt in HCTP, chewing is key because the smaller the food particles, the more surface area our digestive enzymes have to attach and break them down further. And I'm sure you know many of us do not take full advantage of this phase. To tune into this, we suggest the following challenge. Try chewing every bite of one meal all the way to liquid, and then notice what it does for your digestion. If you're up for this challenge, be sure to share your experience with all of us in the Facebook group. Okay, so back to chewing. On average, the mouth produces up to 1.5 quarts of saliva a day, and our entire DNA blueprint is found in our saliva. We may be sharing more than we thought with our partners. Saliva is 98% water but it also contains antibacterial compounds, electrolytes, and mucus. Mucus coats the food for safe travel so that a chip, for example, doesn't scratch your windpipe on the way down. When we start chewing the food in our mouth, we also activate our salivary glands to secrete our first digestive enzyme, an enzyme that begins to break down starch or carbs. Don't worry about the details at this point, we'll go into all the enzymes and their functions in another lecture. When the food is fully coated with mucus, has a watery consistency, and is in smaller pieces, it's ready to travel down the esophagus or food pipe. Once food has been properly mashed up in the mouth, it passes through the pharynx, which is the part of the throat that does the swallowing. And at this point, if we're going to get technical, we no longer call it food. The substance is now known as bolus. So maybe the esophagus should really be called a bolus pipe. As the bolus heads towards the pharynx, down the esophagus, there's a valve that blocks any liquid from going up the nose or down the air tube. And thank goodness because if you've ever laughed while taking a drink, liquid up the nose, hurts. Your esophagus is about eight inches long, and it's made of mucus-lined tissue. And your food, I mean, bolus travels down the esophagus via a method called peristalsis. Peristalsis is a series of wave-like motions that push the food forward through contractions. Because it's involuntary, it means that food will keep going even if we get distracted. In fact, this motion is so strong that if you're standing upside down, it would defy gravity and keep going. Imagine that kind of momentum. As the bolus enters the stomach from the esophagus, we enter phase two of digestion, the gastric phase. The stomach can hold two to four liters of material. As the bolus enters, the stomach muscles begin to expand. And if you eat enough, they can expand all the way down to around your bladder. Just for reference, the stomach is a crescent-shaped, lopsided pouch that normally sits just under your diaphragm. The esophagus enters on the right side so that when we laugh and our stomach contracts, we don't send food back up and out the other end. Genius. The stomach is like an antiseptic holding tank where we kill any unwanted pathogens or bacteria present in the bolus. Remember, our tube is exposed to the outside world, and like a bouncer at the club, we need to screen what makes it in. Acidic gastric juices pour into the stomach and lower the pH to around two, that's enough to burn through your hand. In addition to killing pathogens of the low PH, the stomach's gastric juices continue to break down food before passing it onto the small intestine. Everyone has their role, and the majority of protein digestion occurs in the stomach. After this phase, our mashed up, partially digested food is now called chyme. The stomach releases small amounts of chyme into the first section of the small intestine, two to three teaspoons at a time. Phase three, the Intestinal phase. Now that the food turned bolus turned chyme is in the small intestine, we've entered the intestinal phase, the third phase of digestion. The bulk of carb and fat digestion happens in this phase, as well as any remaining protein digestion. This is also when, what we call the auxiliary organs, the pancreas, the liver, and the gall bladder, get involved. The small intestine has many folds that wraps around for total of 20 feet. And the reason for this is to increase surface area so that like a sponge, our small intestine absorbs most of our nutrients. When chyme is fully broken down into liquid, most of our nutrients are absorbed, the chyme enters the large intestine through the ileocecal valve. Despite its name, the large intestine is actually much shorter, only five feet long, but double in width. It's also called the colon. Good to know in case you get tired of referring to an organ by only one name. I mean, have you noticed that there always seems to be multiple names for a single part of the body. The colon's job is to prepare leftovers from the digestive process to exit the body by absorbing any remaining water and pumping salts back into the body. Water then follows salts. When the water is reabsorbed, what's left are the fibers. These fibers are food for our gut bacteria, who makes sure that any indigestible fiber is fermented to produce all kinds of wonderful nutrients for us, which we'll get into later. Through another active peristalsis, these fibers move to our rectum until they are ready to leave through our anus as waste. Well, we just took you from one end to the other end of the tube. It may have felt like a long journey, but we only traveled about 30 feet. This was just a basic overview so that you now have a picture of the process in your head as we dive deeper. Let's recap. Our alimentary canal or digestive track is where food from the outside world must pass through and be broken down into fuel our body can use. Digestion provides the essential building blocks for survival and growth. So this process can be broken down into three phases. The oral phase, we pop food in our mouth, start the digestive process of breaking down food into smaller molecules, and the mouth is where we start to digest carbs. As we pass into the second phase of digestion, the gastric phase, we move food aka bolus into the stomach which kills any unwanted bacteria. The stomach also breaks down protein. And lastly, the mostly digested food now called chyme enters the third phase, the intestinal phase, where the small intestine finishes the complex job of digestion. Most of the absorption, the good stuff, the gold we reap from the process, takes place here too. For the grand finale, the large intestine extracts any extra water and prepares fiber and other waste material to leave the body, only when our brain gives the final okay of course. And that's the overview of the hollow tubes that make up the center of your body. Does it make you think twice about what you put in and when you know how far it has to travel? To help you visualize this process, we encourage you to take a look at the diagram in the handout provided called The 30 Foot Journey while this information is still fresh in your mind. The more you understand this process, the better you'll be able to help your clients articulate where they are having difficulty and direct them to the appropriate resources. What's something new you learnt in this lecture? Head on over to the Facebook group and let us know. Thanks for joining on this 30-foot journey with me.