Is Your Gut Controlling Your Mind? A Surgeon Breaks Down the Gut-Brain Axis

There was a time when mental health and digestive issues were treated in separate clinics, with little overlap between the two. But today, the emerging science of the gut-brain axis is transforming that old view. One of the clinicians at the forefront of this shift is Dr. Giovanni Leonetti, a general surgeon at Cornerstone Clinic, who has spent years observing the link between gastrointestinal and psychological disorders in his patients.

“I first noticed the connection in patients who came in for gastrointestinal complaints—acid reflux, bloating, abdominal pain—but also happened to suffer from depression, anxiety, or other psychiatric issues,” says Dr. Leonetti. “It wasn’t a coincidence. There was a pattern I couldn’t ignore.”

Understanding the Gut-Brain Axis

At the center of this conversation is the gut-brain axis—a complex, two-way communication system between the gastrointestinal tract and the brain. “It’s bidirectional,” Dr. Leonetti explains. “The brain affects gut function, and the gut, in turn, can influence behavior, cognition, and mood.”

This axis includes a web of communication pathways involving the vagus nerve, hormones, neurotransmitters, and microbial metabolites. It’s not just theory—this system is physically wired into our bodies.

And it's why the gut has earned the nickname, “the second brain.” Packed with over 100 million neurons, the enteric nervous system (ENS) operates largely independently of the central nervous system. It controls everything from enzyme secretion and blood flow to bowel movements—functions that don’t require conscious thought but deeply affect how we feel.

Gut Health and Mental Health

Dr. Leonetti has seen firsthand how improving gut health can improve emotional well-being. One case in particular stood out. “A young woman came to us with bipolar disorder and chronic digestive complaints. We incorporated dietary counseling, probiotics, and encouraged her to join social support groups—alongside her existing psychotherapy. Not only did her gut symptoms improve, but her overall mood stabilized more noticeably as well.”

That example isn’t isolated. Mounting research shows that gut inflammation and microbiome imbalances can interfere with the production of key neurotransmitters—like serotonin, dopamine, and GABA—which are central to mood regulation and cognitive function.

“An imbalanced microbiome can disrupt these chemicals,” says Dr. Leonetti, “leading to mood swings, anxiety, even cognitive fog. It’s not just about digestion—it’s about the brain.”

Conditions most strongly linked to gut health include depression, anxiety disorders, ADHD, and general mood dysregulation.

What We Eat Matters

Diet is a key pillar of gut-brain health. According to Dr. Leonetti, “A diverse diet rich in fiber, whole plant foods, and fermented items helps maintain a healthy microbiome. Think omega-3 rich fish, berries, olive oil, green tea, and fermented foods like kefir or kimchi.”

What to avoid? “Limit alcohol, artificial sweeteners, red meat, added sugars, and ultra-processed foods. These are common gut disruptors.”

The Hype Around Probiotics—Should You Buy In?

The market is flooded with gut health supplements, from probiotic powders to kombucha everything. But Dr. Leonetti urges a more measured view. “Are they helpful? Sometimes. But the effect depends on the individual, the strain of bacteria, and the specific condition. They’re not a cure-all.”

Instead, he recommends incorporating these products thoughtfully, as part of a balanced diet, not as miracle solutions. And always in consultation with a qualified professional.

Stress, the Gut, and the Vicious Cycle

Stress doesn’t just take a toll on your emotional well-being—it directly affects your digestive system, too. According to Dr. Giovanni Leonetti, “Chronic stress triggers and worsens digestive problems. Digestive distress then fuels emotional stress.” This creates a self-perpetuating loop between the brain and the gut. Breaking this cycle requires a combination of physical and emotional strategies. Regular physical activity, adequate sleep (7–8 hours per night), and a balanced diet rich in nutrients can all support gut and mental health. It's also important to limit alcohol, sugar, and processed foods, as they can worsen both stress and digestion. Taking short breaks during intense tasks, practicing mindfulness or meditation, and spending time in nature help regulate stress responses. Equally vital is maintaining social connections—talking to friends, joining support groups, or seeking professional therapy can provide the emotional outlet needed to restore balance between the gut and the brain.

What Pop Culture Gets Wrong

On social media, gut health is often oversimplified or exaggerated. “You’ll see influencers claim that a certain food ‘cures’ depression,” Dr. Leonetti says. “That’s misleading and ignores the complexity and individuality of the gut-brain axis.”

He’s also concerned about the over-commercialization of a field still under scientific exploration. “There’s a danger in reducing gut health to a consumer trend. It needs to be grounded in research and tailored care.”

Know the Signs

Wondering if your gut health could be influencing your mental state—or the other way around? Dr. Giovanni Leonetti notes that the connection often reveals itself through a combination of physical and emotional symptoms. Common signs include frequent stomach discomfort, chronic fatigue, trouble sleeping, food intolerances, and intense sugar cravings. You might also experience unexplained weight gain or loss, skin irritations, recurring migraines, or autoimmune flare-ups. These symptoms can be subtle or persistent, but they often signal an imbalance in the gut-brain axis. If any of these issues continue over time, it’s worth taking a closer look at both your digestive health and your emotional well-being.

Start Simple: 3 Steps to Begin Today

Improving your gut and mental health doesn’t have to be overwhelming. Dr. Leonetti recommends starting with three simple, practical changes. First, increase your fiber intake by adding more fruits, vegetables, legumes, and whole grains to your meals, and make sure you're drinking enough water throughout the day to support digestion. Second, stay physically active—even light daily movement like walking or stretching can positively impact your gut and reduce stress levels. Third, focus on managing stress in small but consistent ways, whether that means setting boundaries, taking breathing breaks, or incorporating mindfulness into your routine. These small steps can lay the foundation for better gut health and emotional balance over time.

The Bottom Line

“Take care of your gut,” Dr. Leonetti says. “Your overall health depends on it.”

The gut-brain connection isn’t just the next wellness trend—it’s a foundational part of how our bodies and minds work together. Understanding it could be the key to healing in both places.