Is Your Gut Controlling Your Mood? The Science Behind the Gut-Brain Axis

Join Dr. James Odell for Season 2 of the Science of Self-Healing Podcast! He's the medical and executive director for BRMI, as well as a practicing naturopathic doctor for over 35 years, and he's here to share with you his extensive knowledge of medicine from a different perspective.

The Bioregulatory Medicine Institute

The Science of Self-Healing Podcast

Your gut isn’t just about digestion—it’s a powerful command center for your mood, immune health, and even how your brain works.

In this episode, Dr. Odell discusses the gut-brain connection and explores how this two-way communication system impacts everything from stress resilience to emotional well-being.

He’ll uncover the fascinating science of the enteric nervous system (your “second brain”), the vagus nerve superhighway, and the trillions of microbes living inside you that produce neurotransmitters like serotonin, dopamine, and GABA. You’ll learn how gut health influences inflammation, stress hormones, mental clarity, and mood—and what happens when the gut ecosystem falls out of balance.

Most importantly, you’ll discover practical, evidence-based strategies to heal from the inside out: from gut-friendly nutrition and probiotics to lifestyle practices that calm both body and mind.

If you’ve ever wondered why bloating, brain fog, anxiety, or low mood might all be connected, this episode will give you the clarity—and the tools—to start shifting your health.

Transcript for: Is Your Gut Controlling Your Mood? The Science Behind the Gut-Brain Axis

Hello, everyone, and welcome to the Science of Self-Healing podcast. For health and wellness knowledge from a different perspective. Produced by the Bioregulatory Medicine Institute, also known as BRMI. We are your source for unparalleled information about how you can naturally support your body's ability to regulate, adapt, regenerate, and self-heal. I'm your host, Dr. James Odell, the medical and executive director for BRMI, as well as a practicing naturopathic doctor for over 35 years. And remember, this podcast is for informational purposes only and is not intended to be a substitute for the direct care of a qualified health professional who oversees and provides unique and individual care. The information here is to broaden our different perspectives and should not be construed as medical advice or treatment. Let's get started.

Introduction: Why the Gut-Brain Connection Matters

Hey there, welcome back! In today’s episode, we’re digging into something super fascinating—the gut-brain connection—and why it matters so much for both immune health and mood balance.

So, here’s the thing: our bodies are crazy complex. Every organ, hormone, and cell is constantly talking to each other in ways we’re only beginning to understand. And honestly, nowhere is this communication more obvious—or more misunderstood—than in the relationship between your gut and your brain.

Ancient Wisdom Meets Modern Science

For centuries, traditional healing systems like Ayurveda and Traditional Chinese Medicine have said digestion is central to mental and emotional health. But Western medicine? Well, it’s really only started catching up in the last few decades. Now, we hear a lot more about the intestinal microbiome and how important it is for overall health.

The Gut-Brain Axis: A Two-Way Street

At the center of all this is something called the gut-brain axis, which is basically a two-way communication network linking your gut and your brain. And here’s the cool part: your gut isn’t just a tube for food. It has its own nervous system, makes neurotransmitters, and is home to trillions of microbes that affect everything from your immunity to your mood.

In the last twenty years or so, research into this has absolutely exploded. Scientists are finding out that the gut plays a huge role in neurological diseases, mental health issues, cognitive function, and even behavior. Conditions like depression, anxiety, fatigue, brain fog—even social behavior—are all tied to gut health. That’s why people often call the gut our “second brain.” Honestly, sometimes it’s even the one running the show. I see it all the time in my practice.

So in this episode, we’re going to explore how the gut and brain are connected, and more importantly, how you can use this knowledge to support your digestive health and your mental health. We’ll talk about the enteric nervous system, the gut microbiome, neurotransmitters, inflammation, stress hormones—you name it. And of course, we’ll finish with some real, evidence-based strategies to heal from the inside out.

The Vagus Nerve: Your Body’s Superhighway

Alright, let’s start by talking about how the gut and the brain actually communicate with each other. This whole system is called the gut-brain axis, and it’s basically a two-way street. It involves the central nervous system, the enteric nervous system, the vagus nerve, your hormones, and even your immune system. They’re constantly chatting through nerves, hormones, and little chemical messengers called cytokines.

And speaking of chatting, let’s talk about the star of the show: the vagus nerve. This thing is like the biological superhighway between the gut and the brain. It runs all the way from your brainstem to your colon, making it the longest cranial nerve in the body. What’s wild is that about 90% of the signals traveling along the vagus nerve go from the gut to the brain, not the other way around. So basically, your gut is giving your brain constant updates, and that means your mood and thoughts are being shaped by your digestive system way more than most of us realize.

The Enteric Nervous System: Your “Second Brain”

Now, along with the vagus nerve, there’s something called the enteric nervous system, or ENS. Some people even call it our “second brain.” It’s this huge network of over 100 million neurons sitting in the lining of your gut. It doesn’t even need your brain to function. It takes care of digestion, blood flow, secretions, and moving things along through the intestines. But here’s the kicker: it also makes neurotransmitters like serotonin, dopamine, and GABA—the same chemicals that regulate mood in your actual brain. And fun fact: your gut actually has more serotonin receptors than your brain does!

The Microbiome: Trillions of Tiny Influencers

Okay, so now let’s shift gears and talk about the microbiome. Inside your gut, there’s this entire ecosystem of bacteria, viruses, fungi, and archaea. Together, they weigh up to 4 pounds and have more genetic material than the rest of your body combined. It’s pretty mind-blowing. And while we tend to think of bacteria as “bad,” the reality is that a healthy, balanced microbiome is absolutely essential—not just for physical health, but for mood and mental health too.

So, how exactly does the microbiome influence your brain? Well, first, many gut microbes actually produce neurotransmitters—the same ones that regulate mood and behavior. For instance, Lactobacillus and Bifidobacterium make GABA, while Enterococcus and Streptococcus help produce serotonin precursors. Those then travel up to the brain either through the vagus nerve or the bloodstream.

Second, these microbes also produce something called short-chain fatty acids when they break down fiber. Those fatty acids reduce inflammation, help protect the blood-brain barrier, and even influence how brain cells function.

Third, since a huge chunk of your immune system is in your gut, microbes help regulate immune responses, which lowers inflammation—a big deal when it comes to mental health.

And fourth, they help maintain the gut barrier. If that barrier gets leaky, toxins can escape into your bloodstream, and that sets off inflammatory reactions in the brain. And that’s when you start seeing symptoms like fatigue, anxiety, or depression.

What Happens When the Microbiome Is Out of Balance?

Now, when the gut ecosystem is out of balance—a state called dysbiosis—things can get rough. Studies have linked dysbiosis to depression, anxiety, schizophrenia, and even autism spectrum disorder. In one really fascinating experiment, germ-free mice (so, mice with no microbes at all) showed abnormal anxiety and social behaviors. But once they got a healthy microbiome, their behavior normalized. That’s how powerful gut microbes are!

Leaky Gut, Inflammation, and the Brain

Alright, let’s keep going and get into inflammation and what’s known as the leaky gut hypothesis. Inflammation is your body’s way of defending itself, but when it becomes chronic, it can do a lot of harm—especially to your nervous system. In fact, many mental health issues like depression, anxiety, bipolar disorder, and even Alzheimer’s show signs of chronic inflammation.

So here’s how this works: your gut lining is made up of cells that form tight junctions, which are like tiny gates that keep gut contents where they belong. But when those gates get loose, you end up with what’s called “leaky gut.” Bacteria and toxins slip into your bloodstream, your immune system freaks out, and you get systemic inflammation.

The immune system releases cytokines—things like IL-6 and TNF-α—that can actually cross into your brain. Once they’re there, they mess with brain chemistry by lowering serotonin and dopamine and revving up your stress response. That leads to fatigue, mood swings, and depression.

And speaking of depression—there’s a clear link between inflammation and depressive symptoms. Research shows that people with major depression often have higher levels of inflammatory markers, even when they’re not sick. Plus, inflammation changes the way tryptophan is used, pushing it away from making serotonin and toward producing toxic compounds like quinolinic acid. The silver lining, though, is that anti-inflammatory treatments—like omega-3s, turmeric, or dietary changes—can really help ease depression for some people.

Stress, Cortisol, and the Gut-Brain Loop

Now, while we’re on the topic of stress, let’s talk about cortisol and the gut-brain loop. Stress activates something called the HPA axis, which makes your adrenal glands release cortisol, your main stress hormone. The problem? Cortisol pretty much shuts down digestion. It slows motility, reduces secretions, weakens your gut lining, and even messes with your microbiome.

And it’s not just one-way—when your gut is inflamed or out of balance, it sends signals back to the brain that increase stress hormones even more. So you end up stuck in this cycle of stress and poor digestion, which can show up as fatigue, insomnia, depression, or immune problems.

Signs Your Gut-Brain Connection Might Be Off

So, how do you know if your gut-brain connection is off? You don’t need something like IBS to see the signs. Some common red flags include bloating, gas, constipation, diarrhea, sugar cravings, brain fog, anxiety, mood swings, poor sleep, or even frequent colds and skin issues. If you’re noticing a combo of these, chances are your gut might be playing a role.

Healing from the Inside Out: Strategies for Gut and Mind

Alright, now let’s wrap this up with some strategies for healing the gut to heal the mind. The key here is that it’s not about one food or one supplement—it’s about creating balance in the whole system.

Diet is a big one. Eating a wide variety of plant foods rich in fiber lays a great foundation. Think fermented foods like sauerkraut or kimchi, prebiotic fibers from garlic and onions, anti-inflammatory fats from salmon or flaxseed, and polyphenols from things like berries, green tea, or even dark chocolate. And, of course, cutting back on processed sugar and refined carbs is huge, since they feed harmful bacteria.

Lifestyle also matters a ton. Exercise regularly, get enough sleep, reduce stress with things like meditation or journaling, and avoid unnecessary antibiotics or painkillers that can mess with your microbiome.

Supplements can help too. Probiotics with well-studied strains like L. rhamnosus, L-glutamine for gut lining repair, zinc carnosine and licorice extract for healing, omega-3 fatty acids for inflammation, and even adaptogens like ashwagandha for stress resilience.

Final Thoughts: The Inseparable Link Between Gut and Mental Health

So, to bring it all together: the gut-brain connection is real, it’s powerful, and we’re only beginning to understand it fully. But what we do know is this—emotional health and digestive health are inseparable. This isn’t just an idea—it’s backed by research and confirmed by real-life experience.

So if you’re struggling with mood swings, anxiety, or depression—or if you just don’t feel like yourself—it might be time to look at your gut. Because healing often starts there.

Alright, that’s all I’ve got for you today. Thanks so much for tuning in, and until next time—take care and be well!

Thank you for your time today, and remember that this podcast is made possible by the Bioregulatory Medicine Institute, also known as BRMI, a nonprofit, global, non political, non commercial institute to promote the science and art of bioregulatory medicine. We extend our gratitude to each and every one of you for listening today, and if you haven't already, make sure to visit us at brmi.online. A treasure trove of invaluable information awaits you there. Connect with us across various social media platforms as well. Come and become a member of our thriving tribe. If you've enjoyed today's episode, we invite you to show your support by rating us, leaving us a review, or sharing the podcast within your circle. Our podcast and mission flourish through sharing, and your participation means the world to us. Our organization is sustained by donations, each of which is tax deductible and fuels projects like this. Visit our website, brmi.online, to contribute or simply to explore the wealth of uncensored and impartial information we offer. No contribution is too small. In just two weeks, we'll be back delving into another captivating topic. Until then, we thank you once again for listening. May wellness and wisdom be your path. Be well.

Bioregulatory medicine is a total body (and mind) approach to health and healing that aims to help facilitate and restore natural human biological processes. It is a proven, safe, gentle, highly effective, drugless, and side-effect-free medical model designed to naturally support the body to regulate, adapt, regenerate, and self-heal. BRMI is a non-commercial 501(c)(3) foundation and will expand and flourish with your support. Our goal is to make bioregulatory medicine a household term.

This article is for informational purposes only and is not intended to be a substitute for the direct care of a qualified health practitioner who oversees and provides unique and individualized care. The information provided here is to broaden our different perspectives and should not be construed as medical advice, diagnosis, or treatment.