What Is the Gut-Brain Connection, and How Does It Affect Your Health?

You’ve probably experienced the gut-brain connection without even realizing it.

Understanding how it works can shed light on why your digestive and mental health symptoms so often overlap — and how your everyday habits can support both.

The gut-brain axis is the two-way communication system connecting the brain and digestive tract through nerves, hormones, immune signals and gut microbes, according to Sameer Berry, MD, a gastroenterologist and a clinical assistant professor of medicine at the NYU Grossman School of Medicine in New York City and the chief medical officer of Oshi Health, which provides multidisciplinary GI healthcare.

“It’s a complex, two-lane highway between our GI system and our brain. For a long time, we thought the gut was just a tube for digesting food, absorbing nutrients and storing and eliminating poop … We’ve learned over the last 20 years that it’s far more complicated than that,” he says.

It involves several components of the body.

• Enteric Nervous System (ENS) Housed within the GI tract and home to more than 500 million nerve cells (neurons) that help control digestive functioning, this network of nerves is nicknamed the “second brain.”

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   “There are more nerve cells here than in the spinal cord,” Dr. Berry says.
• Vagus Nerve Consider the vagus nerve one of the messengers between the ENS and your central nervous system, carrying signals between the two. It helps keep bodily functions running smoothly, including digestion, heart rate, blood pressure, and mood, among others.

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• Gut Hormones Berry says the gut is the body’s largest endocrine organ and it’s known to produce more than 30 hormones, including glucagon-like peptide-1 (GLP-1), ghrelin, and gastrin, that help control digestion, hunger, and metabolism.

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• Gut Microbiome Berry likens this community of microorganisms to a highway patrol, because its makeup helps regulate communication between the gut and brain.

When the system is working well, it helps coordinate digestion, hunger and satiety, bowel rhythm, and the body’s response to stress, says Christina Gentile, PsyD, a clinical health psychologist at UCLA Health in Los Angeles, where she specializes in digestive diseases and the brain-gut connection.

“A healthy gut-brain connection helps the body notice what matters, respond appropriately, and return to baseline. It also helps the brain filter normal digestive sensations, so that not every gurgle, shift, or movement in the gut is interpreted as a threat or treated as an alarm signal,” Dr. Gentile says.

The gut-brain connection may affect:

• Digestion The ENS controls functions ranging from the release of digestive enzymes to the blood flow needed for nutrient absorption.

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   The gut also sends the brain information about fullness, nausea, and discomfort, Berry says.
• Bowel Habits The brain can change how quickly the intestines move. Stress may trigger diarrhea or an immediate need to have a bowel movement in some people, while contributing to constipation in others, Berry says.

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   But when the nervous system is calm, most digestive sensations stay in the background, Gentile says.
• Pain Sensitivity If you’re stressed or sick, or when your sleep, mealtimes, or daily routines are thrown off, you may notice symptoms like nausea, bloating, or abdominal pain, Gentile says. “A sensation that feels mild and manageable in one context may feel more intense, urgent, or harder to ignore when the gut is sensitive or the nervous system is on high alert,” she says.
• Mood Gut health and mental health can influence each other, Gentile says. Digestive symptoms may affect anxiety, sleep, and energy, while anxiety and depression can also alter appetite, nausea, intestinal movement, and pain sensitivity.

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   “Symptoms are real and biological even when stress or emotions are part of the pattern,” she says.
• Quality of Life Unpredictable digestive symptoms may cause people to monitor their bodies closely, worry about finding a bathroom, or avoid eating, working, traveling, and socializing, Gentile says. “The burden is often greater when symptoms are chronic, painful, unpredictable, or embarrassing,” she adds. Research suggests people with irritable bowel syndrome (IBS) have poorer mental health and physical quality of life than the general population with GI-specific anxiety and depressive symptoms.

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• Metabolism, Hunger, and Food Preferences By telling the brain how much a person has eaten and about incoming nutrients, the gut provides information used to regulate energy balance, blood sugar, and insulin sensitivity.

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   Berry says gut-to-brain signaling may also influence cravings.
• Immune Function Seventy percent of the immune system sits in the gut, Berry says.

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   Studies suggest that gut microbes may influence immune cells in both the GI tract and the brain, highlighting the microbiome’s role in immune function.

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Care for the gut-brain connection means support for both digestive health and nervous system regulation, says the psychiatrist Drew Ramsey, MD, the founder of the Brain Food Clinic and author of Healing the Modern Brain and Eat to Beat Depression and Anxiety.

Here are some recommendations.

• Eat a plant-forward diet. Vegetables, fruits, beans, whole grains, nuts, seeds, herbs, spices, and fermented foods support a more varied gut microbiome, Dr. Ramsey says. “If you eat this way, you get a more diverse microbiome, you have more stable bowel movements, and the hope is, over time, you have more resilient mental health [and] better-regulated inflammation, he says.
• Get enough sleep. Sleep supports brain maintenance, healthy gut-brain signaling and overall mood, Ramsey says. You should aim for 7 to 9 hours per night.

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• Prioritize movement. Berry recommends regular physical activity, even if that exercise is brisk walking. Exercise supports intestinal motility, while inactivity can cause constipation in some people.

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• Learn to manage stress. Coping techniques like diaphragmatic breathing can help you respond to stress, Gentile says. Research also suggests that mind-body practices such as yoga, tai chi, and mindfulness may improve stress, sleep, and gut microbial balance.

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• Consider gut-brain therapy. GI-focused cognitive behavioral therapy, acceptance and commitment therapy, gut-directed hypnotherapy, and relaxation-based treatments may reduce symptom-related fear, vigilance, avoidance, and nervous-system arousal, Gentile says.

Berry recommends seeking medical care for symptoms that are new or worsen over time. These include:

• Blood in your stool
• Severe abdominal pain, especially if it wakes you at night
• Unintentional weight loss
• Persistent or worsening diarrhea, constipation, bloating, nausea, or other digestive symptoms
• A family history of gastrointestinal cancer

“See a physician if symptoms are bothering you because there are great treatments that can help people feel better with multidisciplinary care — a doctor, registered dietitian, and brain specialist all together,” Berry says.

You should also seek help when your digestive symptoms come with anxiety, low mood, high stress, or fear of symptoms or gut sensations, Gentile says. “Support may be useful when digestive discomfort leads someone to skip meals, limit activities, monitor symptoms constantly, or plan daily life around their symptoms,” she says.