Gut Feelings: Your Brain and Gut Are More Connected Than You Think
Sitara Mitragotri
Within your abdomen lies an intricate ecosystem filled with trillions of important bacteria: the gut microbiome. The gut serves many functions outside its primary role of digesting food; it is a vital hub for communication with our brain. The "gut-brain axis” represents the bidirectional interactions between the digestive system and the brain and is responsible for many vital processes. For example, when you feel “butterflies in your stomach” during times of stress, it is largely due to changes in blood flow and muscle contractions in your gut as your brain and body mobilize to fight stress. Recent research has delved into how the gut communicates with the brain, suggesting that nurturing the gut-brain axis is vital for achieving mental well-being.
The gut-brain connection predominantly occurs through the enteric nervous system (ENS), located in the gastrointestinal tract. This system consists of sensory neurons, motor neurons, and interneurons, spanning from the esophagus to the rectum (Tresca). The ENS regulates involuntary digestive processes as a part of the Autonomic Nervous System (ANS). Often referred to as the "second brain," the ENS controls secretions, blood flow, release of hormones, and motility—the movement of food through the digestive system (Tresca). It is exceptionally responsive to changes, adjusting its activity based on food intake and disturbances to the gut microbiome, such as infections (Tresca).
At the center of this communication lies the vagus nerve, the primary link between the ENS and the brain (Psychology Today). Sensory receptors in the gut can pick up on crucial changes within the ecosystem, such as nutrient availability or chemical fluctuations (Cleveland Clinic). These signals travel through the vagus nerve to the brain while also relaying motor signals from the brain back to the gut. For example, if the brain detects irritation in the gut, it can activate motor fibers of the vagus nerve to stimulate vomiting (BrainFacts.org).
Your gut microbiome, which includes diverse microorganisms in your intestines, also plays a vital role in regulating your brain. Gut microbes produce key neurotransmitters that influence brain activity via the bloodstream. For example, approximately 95% of serotonin, a neurotransmitter associated with mood regulation, is synthesized in the gut (Appleton). Additionally, microbes like lactobacillus and bifidobacterium generate gamma-aminobutyric acid (GABA), which helps control feelings of anxiety (BrainFacts.org). The gut can also influence the body’s HPA Axis, which controls the body’s stress response system by releasing hormones like cortisol (BrainFacts.org).
When the balance of different microorganisms in the gut is disrupted, also known as dysbiosis, the immune system may release increased levels of pro-inflammatory factors, which can interfere with healthy brain development (Solanki et al.).
Luckily, there are many ways to support your gut health, including staying hydrated and getting enough sleep. Additionally, incorporating certain foods into your diet, such as high-fiber foods like whole grains, nuts, and legumes, or fermented foods like yogurt and kimchi, nourish healthy gut bacteria. By understanding the impact of the gut-brain axis, you can take actionable steps to improve both your physical and mental health.
About the Author
Sitara Mitragotri (‘28) is a freshman at Harvard College concentrating in Psychology and Global Health.
References
The gut-brain connection predominantly occurs through the enteric nervous system (ENS), located in the gastrointestinal tract. This system consists of sensory neurons, motor neurons, and interneurons, spanning from the esophagus to the rectum (Tresca). The ENS regulates involuntary digestive processes as a part of the Autonomic Nervous System (ANS). Often referred to as the "second brain," the ENS controls secretions, blood flow, release of hormones, and motility—the movement of food through the digestive system (Tresca). It is exceptionally responsive to changes, adjusting its activity based on food intake and disturbances to the gut microbiome, such as infections (Tresca).
At the center of this communication lies the vagus nerve, the primary link between the ENS and the brain (Psychology Today). Sensory receptors in the gut can pick up on crucial changes within the ecosystem, such as nutrient availability or chemical fluctuations (Cleveland Clinic). These signals travel through the vagus nerve to the brain while also relaying motor signals from the brain back to the gut. For example, if the brain detects irritation in the gut, it can activate motor fibers of the vagus nerve to stimulate vomiting (BrainFacts.org).
Your gut microbiome, which includes diverse microorganisms in your intestines, also plays a vital role in regulating your brain. Gut microbes produce key neurotransmitters that influence brain activity via the bloodstream. For example, approximately 95% of serotonin, a neurotransmitter associated with mood regulation, is synthesized in the gut (Appleton). Additionally, microbes like lactobacillus and bifidobacterium generate gamma-aminobutyric acid (GABA), which helps control feelings of anxiety (BrainFacts.org). The gut can also influence the body’s HPA Axis, which controls the body’s stress response system by releasing hormones like cortisol (BrainFacts.org).
When the balance of different microorganisms in the gut is disrupted, also known as dysbiosis, the immune system may release increased levels of pro-inflammatory factors, which can interfere with healthy brain development (Solanki et al.).
Luckily, there are many ways to support your gut health, including staying hydrated and getting enough sleep. Additionally, incorporating certain foods into your diet, such as high-fiber foods like whole grains, nuts, and legumes, or fermented foods like yogurt and kimchi, nourish healthy gut bacteria. By understanding the impact of the gut-brain axis, you can take actionable steps to improve both your physical and mental health.
About the Author
Sitara Mitragotri (‘28) is a freshman at Harvard College concentrating in Psychology and Global Health.
References
- Tresca, Amber J. “The Anatomy of the Enteric Nervous System.” Verywell Health, 26 Sept. 2023, www.verywellhealth.com/enteric-nervous-system-5112820.
- Professional, Cleveland Clinic Medical. “The Gut-Brain Connection.” Cleveland Clinic, 1 May 2024, my.clevelandclinic.org/health/body/the-gut-brain-connection.
- “Gut-Brain Axis.” Psychology Today, www.psychologytoday.com/us/basics/gut-brain-axis. Accessed 30 Oct. 2024.
- The Gut and Brain: A Surprising Connection. www.brainfacts.org/brain-anatomy-and-function/body-systems/2024/the-gut-and-brain-a-surprising-connection-012524.
- Appleton, Jeremy. The Gut-Brain Axis: Influence of Microbiota on Mood and Mental Health. 1 Aug. 2018, pmc.ncbi.nlm.nih.gov/articles/PMC6469458.
- Solanki, Riddhi, et al. “Emerging Role of Gut Microbiota Dysbiosis in Neuroinflammation and Neurodegeneration.” Frontiers in Neurology, vol. 14, May 2023, https://doi.org/10.3389/fneur.2023.1149618.
- Bsn, Megan Dix Rn. “Signs of an Unhealthy Gut and What to Do About It.” Healthline, 29 Jan. 2024, www.healthline.com/health/gut-health#what-to-do.