Here's what you need to know about gut health

Added: 2026-05-30

[00:00:00]Most gut conditions that you've heard of, like IBS, leaky gut, food sensitivities, and small intestinal bacterial overgrowth, they're not really totally distinct separate diseases.

[00:00:10]They're more like different entry points into the same underlying problem. So, treating them one at a time almost never works. They are multifactorial. You've got to understand the root, the whole gut system. And when you understand how the whole system works together, you understand how these gut conditions fit into that wider picture and what you can do about them. And that is what we're going to go through in this video. So, let's get into it. Firstly, the gut is actually outside your body. It is a tube that runs from your mouth to your anus.

[00:00:37]And nothing is actually inside your body until it crosses the single layer of intestinal epithelial cells and into your blood. And substances cross through these cells or between them through tight junctions, which tightly control what is allowed through. The gut's surface area is about 32 square meters, making it the body's largest external interface. So, being outside the body, being an external interface, that of course means that the barrier between the outside world, your gut, and the inside world, your body, is very important. Absorption of things from the gut into the blood is very tightly controlled. We want to keep bad things out and let good things in. And that gut barrier is not just one layer, but more like four layers. You have the mucus layer, which is a viscous gel coating the epithelium. And this mucus traps microbes and carries antimicrobial peptides and secretory immunoglobulin A.

[00:01:31]The outer layer of mucus is where our gut bacteria live, and the inner layer is sterile. Then you have the epithelial cell layer, which is just one cell thick and it has several specialized cell types, like enterocytes, which absorb nutrients, goblet cells secrete mucus, Paneth cells release antimicrobial defensins, enteroendocrine cells release gut hormones, and M cells sample antigens. And between these epithelial cells are tight junctions that tightly control what is allowed through that epithelial cell layer. And the opening of tight junctions is regulated by zonulin, which is released in response to gluten in sensitive people and gram-negative bacteria. And then underneath the epithelium is the lamina propria, which is connective tissue that is packed full of immune cells ready to respond to anything that breaches through the upper defense layers. So, leaky gut really is a failure of multiple of these defense layers.

[00:02:24]Substances like endotoxin have to make their way all the way through these four layers in order to reach the blood and start causing systemic problems. Each of these layers can be damaged by specific inputs. Low fiber damages the mucus.

[00:02:38]Alcohol and nonsteroidal anti-inflammatory drugs damage the epithelial layer. Gluten and dysbiosis loosen the tight junctions and chronic stress disregulates the immune layer.

[00:02:49]And I know a lot of guys who are attacking their gut barrier through all four of these at the same time. Like they drink a lot. They're on painkillers or other medications. They eat processed food with no fiber. They're chronically stressed because of work or money or family problems. And that is a perfect recipe for gut problems. So, we've spoken about the barrier. Let's talk about what sits on top of that barrier, which is the microbiome. The microbiome is actually an organ by definition because it has a stable structure, specific functional outputs, it communicates with other organs, and there is measurable disease when it's disrupted. Most of the 38 trillion microbes in the gut live in the colon, the large intestine, because transit is slow. There's no bile here, and it's anaerobic. It's a very low oxygen environment. Small intestine bacterial overgrowth happens when bacteria populations from the colon colonize the small intestine where they shouldn't be.

[00:03:41]The microbiome has functional outputs, like I said. So, some of the main ones are short-chain fatty acids. Butyrate fuels colonocytes. So, butyrate is actually the main energy source for colonocytes. Propionate goes to the liver and modulates gluconeogenesis, and acetate enters systemic circulation and has a bunch of benefits including in the brain. The microbiome also produces vitamins like K2, B12, B7, B9, and B2.

[00:04:08]It also makes neurotransmitters like GABA, dopamine, and serotonin precursors, and it modifies bile acids.

[00:04:15]If you have a diverse microbiome, it fills every possible niche in that environment, leaving no room for pathogens to colonize any niches. So, when you take antibiotics, that can clear out niches indiscriminately, allowing pathogens to come in and colonize certain niches. And this is why you can often see C. difficile infection after a round of antibiotics. The diversity of the microbiome correlates with its functional capacity. A low-diversity microbiome can't ferment all fibers, it can't produce the full short-chain fatty acid profile, it can't synthesize all of the vitamins, and it can't outcompete every pathogen. So, microbial diversity is something that we want. The gut also has its own nervous system, and that is wired directly into the brain. The enteric nervous system, the gut nervous system, has 500 million neurons, and it can work autonomously without the brain to digest, secrete, and contract. So, the enteric nervous system is sometimes called a second brain. The vagus nerve is the main link between the gut and the brain, and about 90% of those vagal fibers go from the gut to the brain. So, it is the brain receiving information from the gut rather than the brain sending information to the gut most of the time.

[00:05:28]And this gut-brain axis runs on three communication channels, uh neural communication via the vagus nerve, which happens in milliseconds, endocrine communication through gut hormones like ghrelin, CCK, and GLP-1 on the scale of like minutes, and then immune communication through cytokines and endotoxin over hours to days, and that is the most like long-lasting one. And the microbiome influences all three of these pathways. It produces neurotransmitters. It produces short-chain fatty acids, which signal in minutes, and it modulates inflammation.

[00:05:59]Now, something that you will have heard connected with gut health is fiber. And instead of thinking of fiber as just one simple category, it's more useful to identify the different subcategories, and there are about four main ones. You have soluble, fermentable, viscous fiber found in things like oats, apples, and psyllium. And this slows gastric emptying. It binds bile acids, lowers LDL, and flattens glucose. Then there's soluble, fermentable, non-viscous fiber, also called prebiotics, found in things like onions, garlics, leeks, and asparagus. And this selectively feeds good bacteria like Bifidobacterium and Lactobacillus. Then there's insoluble, poorly fermentable fiber like wheat bran and vegetable skins. And this adds bulk to the stool and stimulates gut motility. And then there is resistant starch found in things like cooked and cold potatoes, rice, and pasta, and also in green bananas and legumes. And resistant starch is fermented by Ruminococcus bromii to produce butyrate, one of those short-chain fatty acids I mentioned earlier. So, more important than total fiber is making sure that you get some of each of these four different types. Of course, a lot of carnivore guys will say that you don't need fiber or that fiber is actually harmful. And many people certainly do see an improvement in their symptoms when they cut out fiber. That can't really be denied, but relief from symptoms doesn't mean that the root problem is fixed.

[00:07:20]Carnivore is basically the most extreme elimination diet out there. If you are reacting to a specific plant trigger, then removing every plant at once will obviously relieve uh your symptoms. It also starves any bacterial overgrowth, so controls symptoms by starvation, not by fixing the underlying ecology. And then the ketogenic state itself is anti-inflammatory independent of fiber.

[00:07:44]So, it could be that the ketosis is what is relieving gut symptoms rather than removing the fiber itself. So, really you can think of carnivore like a reset.

[00:07:53]It's definitely a useful short-term tool, but the goal is ultimately to restore full function, not just temporary relief from symptoms by avoiding triggers. We want to fix the underlying issue and then reintroduce fiber gradually to rebuild a diverse microbiome that defends you long-term.

[00:08:11]The migrating motor complex is a programmed sequence of contractions that sweeps residual food, dead cells, and bacteria from the upper GI tract down into the colon. And it only works when you're fasted. So, you have to leave about 3 or 4 hours in between meals to allow it to work. If you have any calories between meals, the migrating motor complex turns off and digestion mode turns on. So, you need no calories between meals, no snacking, no having like coffee with milk or energy drinks or things like that. Just water, maybe black coffee, maybe plain tea. And when you hear your gut rumbling, that is the migrating motor complex working. Vagal tone modulates the migrating motor complex. That's from the vagus nerve that I mentioned earlier. High vagal tone when you're relaxed and low stress and in like a parasympathetic state, that supports the migrating motor complex. And chronic stress suppresses it and therefore increases your risk of small intestine bacterial overgrowth because food debris and pathogens are not being swept out of the small intestine properly. Eating right before bed also delays the nocturnal migrating motor complex, so you should stop eating about 2 or 3 hours before bed so that it can kick in about when you fall asleep and work all through the night instead of missing out on the first couple of hours of that sweeping because you ate right before bed. A healthy fasted stomach has a pH of about 1.5 to 3, which is very acidic. And this acid is hydrochloric acid secreted by parietal cells in the stomach lining. And the acid has four main jobs. It kills most of the bacteria and parasites in the food that you ingest. It unfolds proteins so that enzymes can access the peptide bonds to break them down. It activates pepsin, which is an enzyme that breaks down proteins. And it triggers secretin and CCK. Low stomach acid is actually more common than high stomach acid in adults. And stomach acid decreases with age, chronic stress, H.

[00:10:05]pylori infection, and PPI use. And when your stomach acid is too low, your risk of SIBO increases, nutrients like B12 and iron and magnesium aren't absorbed properly, protein digestion is impaired, and your risk of gut infection increases. And the problem is that low stomach acid symptoms are often the same as high acid symptoms like reflux. So, you might go into a doctor with symptoms that look like high stomach acid, they put you on a proton pump inhibitor, and then if you had low stomach acid, that is going to make it even lower, and it's going to make your problems like even worse. The gut is like a central hub that's connected to everything else, but especially the liver, brain, the skin, and the immune system. All venous blood from the gut drains via the hepatic portal vein into the liver before reaching systemic circulation. So, the liver filters everything that is absorbed in the gut before sending it out to the rest of the body. And the gut and the liver work together to circulate and modify bile acids. We discussed the gut-brain axis earlier, but a little example, if you've got a leaky gut, like your tight junctions are too permeable, that can allow things like endotoxin to get through your gut into your blood, which will then trigger an immune response, including in the brain, causing neuroinflammation and brain fog.

[00:11:19]So, things like brain fog and brain problems can start from the gut. A lot of skin conditions as well start from the gut. So, that same kind of mechanism, leaking endotoxin into circulation, and can drive skin inflammation. And a lot of skin conditions like acne and eczema all have certain gut microbiome signatures. And then one example from the immune system, T regulatory cells suppress inappropriate immune responses like autoimmune attacks on your own body. And butyrate, that short-chain fatty acid produced by our gut microbiome, that butyrate induces differentiation of T reg cells via HDAC inhibition. And this means that a diet that's deficient in fermentable fiber causes butyrate levels in the colon to drop, and that impairs this specific pathway of differentiating peripheral T regulatory cells, and that contributes to a permissive environment for systemic inflammation, and it increases the statistical risk of autoimmune disorders. And the gut is even connected to hormones. There's something called the estrobolome, which is the gut bacteria involved in estrogen metabolism. So, your liver tags used estrogen with a marker called glucuronide, so it can be excreted in bile into the gut and then pooped out.

[00:12:29]But some gut bacteria produce an enzyme called beta-glucuronidase, which strips that marker off of estrogen, reactivating the estrogen and allowing it to be reabsorbed back into circulation. So, the state of your gut directly affects how much estrogen you have in your body. If you have dysbiosis and you have too much beta-glucuronidase activity, that means that lots of estrogen is getting reactivated and reabsorbed. So, your estrogen is going to be higher even when your production of estrogen is normal. So, for men, this matters because it shifts your testosterone to estrogen ratio in the wrong direction. Like, you can have normal testosterone production, not even be producing that much estrogen, and still end up with too much estrogen because your gut is recycling too much of it instead of excreting it. And this is why if you're a guy trying to optimize your hormones, your testosterone, you can't be too narrow-sighted and just think about testosterone. Like, your gut health is a huge part of the equation, and most people overlook this. Like many other things in the body, the gut runs on a circadian clock driven by clock genes.

[00:13:30]The central clock is the suprachiasmatic nucleus in the brain, and this is entrained by light. And peripheral clocks in the gut are entrained mainly by meal timing. And across the span of the day, things like stomach acid, enzyme release, motility, they all vary based on the time of day. And about 15 to 20% of the microbial taxa in your gut show daily oscillations in abundance.

[00:13:54]So, you have a slightly different microbiome at 8:00 a.m. compared to 8:00 p.m. And circadian misalignment means that your peripheral clocks, like your gut, are out of sync with the central clock in your brain. And this can happen with eating late at night, irregular meal times, shift work, jet lag, and poor light environment like bright lights and blue lights at night, and then staying inside all day when you should be out in the sun. Blood sugar control is lower in the evening, so you shouldn't be eating high-carb meals in the evening. It's much better to have those in the morning. Microbiome diversity drops when your meal times are kind of irregular and erratic and not consistent, and inflammation rises systemically when your clocks are desynchronized. So, practically, you should be eating during the day and fasting overnight. Front-load your calories earlier in the day when your body is better prepared to take those on. Stop eating about two or three hours before bed, and get morning light into your eyes within an hour of waking up to entrain your circadian clock. And then in the evening, reduce bright and blue lights to let your brain know that it's night time. One of the big issues with gut problems, both causing gut problems and the result of gut problems, is chronic low-grade inflammation. This is slow, it's kind of mild, systemic, all throughout your body, and it doesn't resolve itself. And this low-level inflammation is implicated in aging, heart disease, type 2 diabetes, non-alcoholic fatty liver disease, depression, neurodegeneration, and autoimmune conditions. And a compromised gut barrier is one of the biggest sources of this inflammation. And there are about six steps that lead to this inflammatory state. First, there's some trigger that compromises the gut barrier like low fiber diversity, dysbiosis, low stomach acid, a sluggish migrating motor complex, chronic stress, or circadian misalignment. There's some initial insult like this, and that leads to the barrier becoming more permeable. And then endotoxin and antigens leak out into the blood. And then the immune system gets activated to fight these foreign invaders, and it doesn't deactivate because there is an ongoing inflow of endotoxin and antigens through that leaky gut barrier. The immune activation means that inflammation spreads everywhere throughout the body like in the brain, and in the liver, in the skin causing skin issues, causing metabolic issues. And then the inflammation itself further degrades the gut barrier, worsens dysbiosis, and suppresses vagal tone. So, it is just a vicious negative loop. And most gut conditions like IBS, small intestine bacterial overgrowth, leaky gut, food sensitivities, these are all just different entry points into this same self-reinforcing inflammatory loop. And if you want to solve them, you need to address every point of this loop, every step in this entire system in the gut.

[00:16:42]So, let's summarize what I've taught you in this video. The gut is outside your body, so the barrier between the gut and the body is very important, and it must be maintained. That barrier is made of mucus, epithelial cells, tight junctions, and immune tissue. And if this barrier is compromised, endotoxin can leak into the blood and cause systemic inflammation. The microbiome is a functional organ like any other organ in the human body, and fiber is its fuel source. There are four types of fiber, and we should generally try to get some of all of these: soluble fermentable viscous fiber, soluble fermentable non-viscous fiber, insoluble fiber, and resistant starch. The enteric nervous system is autonomous. It can work by itself, and it's connected to the brain via the vagus nerve. Mostly, it is the gut sending signals to the brain. The migrating motor complex sweeps clean the gut, and it requires a fasted state to work. Stomach acid is required for killing pathogens and degrading proteins and absorbing nutrients. The gut runs on a circadian clock entrained largely by meal timing. And inflammation can spread from a leaky gut all throughout the body, and lots of health problems throughout the body start in the gut. I hope you learned some new things about the gut today. If you only do three things from this video, I recommend you start leaving 3 or 4 hours between meals to let your migrating motor complex do its thing, and stop eating 2 or 3 hours before bed. Get morning sunlight in your eyes within an hour of waking up to entrain your central circadian clock.

[00:18:12]And thirdly, manage your stress and slow down before meals. Like, turn on that parasympathetic rest and digest nervous system by taking some deep breaths and calming down. Chronic stress is terrible for your digestion and your gut health as a whole. If you want the practical side of all of this, like, exactly what to eat, how to structure your meals, and how to build a diet that supports the gut system that I've just walked you through, I go into all of that in my nutrition guide, which is linked in the description. And if you found this video useful, please subscribe. I plan to go a lot deeper into gut health in future videos. Thank you for watching, and I will see you in the next one.