The Gut-Brain Connection: A Functional Dietitian’s Take on Why Your Gut Health is Important for Your Mental Health

Did you know your gut and brain are in constant communication? It’s true—your gut health can play a major role in how you think, feel, and even respond to stress. This connection is so significant that the gut is often referred to as “the second brain.”

Research over the past decade has uncovered just how closely these two systems are linked, revealing how your gut health can impact your overall well-being. Here’s the kicker: if your gut isn’t happy, your brain can feel the effects too. Conditions like anxiety, depression, and even cognitive decline have been linked to poor gut health (1).

More and more research is becoming available on the intimate relationship between gut health and its impact on mental health. A recent study in 2023 found that 38% of patients hospitalized for IBS (irritable bowel syndrome) also suffered from anxiety (2). 

But don’t worry—it’s not all bad news! There are specific, actionable steps you can take to improve your gut health and your gut-brain connection—even if you’ve been struggling with constipation, loose stools, bloating, and reflux for decades, or received an IBS diagnosis, and were sent on your way.

What Exactly Is Gut Health?

When people talk about “gut health,” they’re referring to the balance and function of the trillions of microorganisms that live in your digestive system, mainly your large intestine. Collectively, these tiny organisms make up your gut microbiome, a community of bacteria, fungi, viruses, and other microbes that work together to keep you healthy.

A healthy gut microbiome is diverse and abundant in beneficial bacteria, which support essential functions like digesting food, absorbing nutrients, and protecting your body from harmful invaders (3). But these bacteria don’t just influence your digestion—they also affect your mood, cognition, and even learning ability.

When the gut microbiome is disrupted—a condition called dysbiosis—it can lead to imbalances and manifest in digestive symptoms like bloating and constipation, as well as anxiety, to name a few. For example, having an overgrowth of opportunistic bacteria like Escherichia coli, Staphylococcus aureus, or Desulfovibrionaceae can negatively affect bowel motility and contribute to constipation (13). Dysbiosis is increasingly recognized as a significant contributing factor to a range of health issues, including gastrointestinal disorders, autoimmune diseases, and metabolic syndromes (7,8).

But the role of your gut doesn’t stop there.

Your gut is connected to your brain.

Your Gut and Brain Connection: It’s a Two-Way Street

Have you ever heard the phrase “gut feeling”? It turns out there's a real scientific reason behind it. The gut and brain are intricately connected through what is known as the gut-brain axis. The gut-brain axis is bidirectional, meaning the gut can influence the brain, and the brain can influence the gut—but more recent research indicates that your gut can actually exert more influence on your brain than your brain on your gut.

The vagus nerve is a key player in the gut-brain axis. The vagus nerve extends from the brainstem to the gut, where it unravels itself and penetrates the gut wall, playing a critical role in both your nervous system and food digestion.

The vagus nerve acts as a superhighway between the gut and brain. It oversees a vast array of crucial bodily functions, including control of mood, immune response, digestion, and heart rate (5). This nerve transmits signals about the state of the gut, including the presence of nutrients and the overall health of the microbiome, directly to the brain, and the brain can send messages directly to the gut.

Think of it this way: the vagus nerve is like your body’s internal news network, sharing updates on digestion and overall gut health. But if your vagus nerve isn’t functioning as it should and/or your gut microbiome isn’t balanced, the communication signals can shift toward stress, depression, anxiety, GI symptoms like constipation and bloating, and inflammation.

The Role of Gut Bacteria in Mental Health

Here’s where things get even more interesting. Your gut bacteria don’t just passively exist; they actively influence your brain function. How? The gut microbiome can influence your mood!

One of the most well-known neurotransmitters affected by gut bacteria is serotonin. Early research showed a lot of excitement about how 80-95% of your body’s serotonin is produced in the gut (3,6). However, as more research continues to emerge on the fascinating role of gut health, the serotonin produced in your gut does not appear to cross the blood-brain barrier and may not exert an influence on your mental health. But that doesn’t mean serotonin produced in your gut isn’t important! As research on gut health evolves, we are realizing the importance serotonin has on gut motility (AKA helping you poop and move food through your digestive tract) by causing the smooth muscles of the colon to contract and relax (13).

Where your gut bacteria can really impact your mental health is through short-chain fatty acids (SCFAs). SCFAs are created when your healthy gut bacteria ferment the dietary fiber you eat. SCFAs can influence inflammation, brain neurotransmitters, cognitive function, and even the vagus nerve (14).

9 Signs Your Gut Is Out of Balance

Your gut is always giving you clues about its health. Here are nine signs it’s time to do something about your gut health:

1. You experience frequent gas and bloating.
2. You have fewer than one full and complete bowel movement per day (a type 3 or 4 on the Bristol Stool chart).
3. You have undigested food in your stool.
4. You have to strain to produce a bowel movement.
5. You feel overly full after meals.
6. You have loose or unformed stools.
7. You experience anxiety and a nervous stomach.
8. You feel fatigued or sluggish after eating.
9. You experience acid reflux.

If you experience one or more of these symptoms, it’s likely time to focus on improving your gut health

How to Improve Gut Health and Mental Health

The connection between your gut and brain means that caring for your gut can have wide-reaching benefits for both your body and mind.

Eat for Gut Health

The human microbiome is home to thousands of bacteria strains. Diets that are extremely limited or lacking in diversity are more prone to experiencing gut dysbiosis (9). Diets rich in fiber, fermented foods, and polyphenols (plant-based compounds) help nourish beneficial gut bacteria and encourage diversity (4).

• Fiber: Fiber supports the growth of bacteria that produce SCFAs, which have anti-inflammatory effects and improve gut barrier function as well as your gut-brain connection (4). Foods like whole grains, vegetables, fruits, and seeds are great sources of fiber.
• Fermented Foods: Fermented foods have long been a cornerstone for gut health. These foods provide probiotics and live bacteria that can enhance the health of your microbiome (10). Examples include yogurt, kefir, sauerkraut, kimchi, and miso.
• Polyphenols: Found in foods like berries, green tea, dark chocolate, and nuts, polyphenols encourage the growth of healthy bacteria (4).

Another way to support your gut health is to avoid or limit certain foods. Processed foods high in sugar, unhealthy fats, and artificial additives can promote the growth of harmful bacteria and have been associated with poor health outcomes, including depression (4). It's also wise to be cautious with artificial sweeteners, as some studies suggest they may negatively impact gut microbiota (4).

If you’ve tried to increase or limit these foods and noticed an increase in symptoms like constipation, gas, bloating, and/or diarrhea, that’s a sign that the bacteria, fungi, or digestive function in your gut is disrupted, and you may need lab testing to uncover what’s causing your symptoms. Book a case review call so we can help you figure out the lab testing that can help determine what exactly is causing your symptoms and the exact next steps to take.

Stay Active

Exercise doesn’t just benefit your heart and muscles—it also supports your gut. Regular physical activity has been shown to increase microbial diversity and boost the production of beneficial short-chain fatty acids (SCFAs) (11). Whether it’s a brisk walk, yoga, or weightlifting, moving your body is a win for your gut and brain alike when done in moderation. Excessive cardio or HIIT can actually increase stress on your body, impair digestion, and make your bloating worse.

Managing Stress

Chronic stress can wreak havoc on your gut, leading to increased inflammation, changes in gut motility, and even shifts in your gut bacteria composition (12). Luckily, there are plenty of ways to manage stress effectively to support your gut health and mental health.

Here are some of my favorite ways to manage stress.

• Neural reprogramming practices like the Gupta Program or Vital-Side (use Kerri10 for 10% off at checkout)
• Journaling
• Yoga
• Spending time in nature
• EMDR therapy

Remember the vagus nerve we talked about earlier? Stimulating your vagus nerve can also help reduce stress and promote gut health. Try techniques like box breathing (inhale for 4 counts, hold for 4, exhale for 4, hold for 4), gargling, or humming to activate this important nerve and support your gut health (5).

Taking Care of Your Gut Health for Better Mental Health

The gut-brain connection shows us that gut health is about much more than just digestion—it’s essential for mental well-being. When you take care of your gut microbiome through proper nutrition, regular exercise, and stress management, you’re also supporting your emotional resilience and cognitive health. Feel like you already do most of these things but are still struggling with chronic bloating, constipation, loose stools, anxiety, and reflux? This is often rooted in dysbiosis, infections, significant maldigestion, or inflammation. Schedule a case review so we can dig deeper to identify the root cause of your symptoms and the immediate action steps to take to resolve them for good.

References:

1. Socała, K., Doboszewska, U., Szopa, A., Serefko, A., Włodarczyk, M., Zielińska, A., Poleszak, E., Fichna, J., & Wlaź, P. (2021). The role of microbiota-gut-brain axis in neuropsychiatric and neurological disorders. Pharmac!ological Research, 172, 105840. https://doi.org/10.1016/j.phrs.2021.105840

2.Tarar, Z.I., Farooq, U., Zafar, Y. et al. Burden of anxiety and depression among hospitalized patients with irritable bowel syndrome: a nationwide analysis. Ir J Med Sci 192, 2159–2166 (2023). https://doi.org/10.1007/s11845-022-03258-6

3. Khlevner, J., Park, Y., & Margolis, K. G. (2018). Brain–Gut Axis Clinical Implications. Gastroenterology Clinics of North America, 47(4), 727. https://doi.org/10.1016/j.gtc.2018.07.002

4. Berding, K., Vlckova, K., Marx, W., Schellekens, H., Stanton, C., Clarke, G., Jacka, F., Dinan, T. G., & Cryan, J. F. (2021). Diet and the Microbiota–Gut–Brain Axis: Sowing the Seeds of Good Mental Health. Advances in Nutrition, 12(4), 1239. https://doi.org/10.1093/advances/nmaa181

5. Breit, S., Kupferberg, A., Rogler, G., & Hasler, G. (2018). Vagus Nerve as Modulator of the Brain–Gut Axis in Psychiatric and Inflammatory Disorders. Frontiers in Psychiatry, 9, 44. https://doi.org/10.3389/fpsyt.2018.00044

6. Reigstad, C. S., Salmonson, C. E., Szurszewski, J. H., Linden, D. R., Sonnenburg, J. L., Farrugia, G., & Kashyap, P. C. (2014). Gut microbes promote colonic serotonin production through an effect of short-chain fatty acids on enterochromaffin cells. The FASEB Journal, 29(4), 1395. https://doi.org/10.1096/fj.14-259598

7. DeGruttola, A. K., Low, D., Mizoguchi, A., & Mizoguchi, E. (2016). Current understanding of dysbiosis in disease in human and animal models. Inflammatory Bowel Diseases, 22(5), 1137. https://doi.org/10.1097/MIB.0000000000000750

8. Hrncir, T. (2022). Gut Microbiota Dysbiosis: Triggers, Consequences, Diagnostic and Therapeutic Options. Microorganisms, 10(3), 578. https://doi.org/10.3390/microorganisms10030578

9. Oriach, C. S., Robertson, R. C., Stanton, C., Cryan, J. F., & Dinan, T. G. (2016). Food for thought: The role of nutrition in the microbiota-gut–brain axis. Clinical Nutrition Experimental, 6, 25-38. https://doi.org/10.1016/j.yclnex.2016.01.003

10. Leeuwendaal, N. K., Stanton, C., & Beresford, T. P. (2022). Fermented Foods, Health and the Gut Microbiome. Nutrients, 14(7), 1527. https://doi.org/10.3390/nu14071527

11. Ortiz-Alvarez, Lourdes MSc1,2,*; Xu, Huiwen MSc1,2,*; Martinez-Tellez, Borja PhD3. Influence of Exercise on the Human Gut Microbiota of Healthy Adults: A Systematic Review. Clinical and Translational Gastroenterology 11(2):p e00126, February 2020. | DOI: 10.14309/ctg.0000000000000126 

12. Konturek PC, Brzozowski T, Konturek SJ. Stress and the gut: pathophysiology, clinical consequences, diagnostic approach and treatment options. J Physiol Pharmacol. 2011 Dec;62(6):591-9. PMID: 22314561.

13. Pan, R., Wang, L., Xu, X., Chen, Y., Wang, H., Wang, G., Zhao, J., & Chen, W. (2022). Crosstalk between the Gut Microbiome and Colonic Motility in Chronic Constipation: Potential Mechanisms and Microbiota Modulation. Nutrients, 14(18), 3704. https://doi.org/10.3390/nu14183704

14. O'Riordan, K. J., Collins, M. K., Moloney, G. M., Knox, E. G., Aburto, M. R., Fülling, C., Morley, S. J., Clarke, G., Schellekens, H., & Cryan, J. F. (2022). Short chain fatty acids: Microbial metabolites for gut-brain axis signalling. Molecular and Cellular Endocrinology, 546, 111572. https://doi.org/10.1016/j.mce.2022.111572