Last Updated: October 2025

Most people are surprised to learn that the health of their gut directly affects their brain. In fact, nearly 90% of the body’s serotonin—the neurotransmitter responsible for mood and focus—is produced in the digestive tract. When the gut becomes imbalanced, inflamed, or “leaky,” toxins and inflammatory molecules can enter the bloodstream, cross the blood-brain barrier, and trigger neuroinflammation. This powerful link, known as the gut-brain axis, plays a critical role in memory, mood, and long-term cognitive health.

At The Carroll Institute in Sarasota, Dr. Garland Glenn, DC, PhD, AFMC integrates gut health as a cornerstone of brain restoration through the Bredesen ReCODE Protocol and Functional Medicine testing. Addressing the root causes of gut dysfunction often leads to profound improvements in focus, energy, and cognition.

Understanding the Gut-Brain Axis

The gut-brain axis is a two-way communication network linking your intestinal microbiome to your central nervous system. This connection involves the vagus nerve, hormones, neurotransmitters, and immune molecules. When your gut is balanced, it sends healthy, calming signals to the brain. When it’s imbalanced, it sends danger signals that promote inflammation and oxidative stress.

Emerging research from the National Institutes of Health shows that gut bacteria influence everything from appetite and sleep to decision-making and memory consolidation. This means that addressing gut health isn’t just about digestion—it’s about rebuilding the foundation of neurological health.

Leaky Gut, Leaky Brain

One of the most common yet overlooked conditions affecting brain health is intestinal permeability, commonly known as “leaky gut.” When the intestinal lining becomes damaged, it allows bacterial toxins (lipopolysaccharides or LPS) to enter the bloodstream. These molecules can travel to the brain, where they trigger inflammation and microglial activation—two hallmarks of cognitive decline.

Over time, this process leads to what researchers call “leaky brain,” where the blood-brain barrier becomes compromised. This allows even more toxins to reach neurons, creating a vicious cycle of inflammation and degeneration.

Signs of Gut-Brain Imbalance

• Brain fog, forgetfulness, or difficulty concentrating
• Digestive issues such as bloating, constipation, or food sensitivities
• Chronic fatigue or low motivation
• Frequent anxiety, irritability, or depression
• Autoimmune conditions or skin inflammation
• Unexplained weight gain or blood sugar imbalance

Because the gut and brain communicate constantly, imbalances in one often show up as symptoms in the other. This is why patients with irritable bowel syndrome (IBS), for example, are more likely to experience anxiety or brain fog—and why restoring gut balance often leads to clearer thinking and better mood regulation.

Functional Medicine Testing for Gut Health

Dr. Glenn uses advanced Functional Medicine lab testing to identify the root causes of gut dysfunction, including:

• Comprehensive stool analysis to assess microbiome diversity and inflammation
• Food sensitivity and food antibody testing
• Leaky gut markers such as zonulin and LPS
• Testing for parasites, candida, or small intestinal bacterial overgrowth (SIBO)

These insights guide a personalized gut restoration plan designed to calm inflammation and restore the gut-brain connection.

Restoring Gut and Brain Balance

Healing the gut requires a step-by-step approach that removes irritants, repairs the intestinal barrier, and rebuilds a healthy microbiome. At The Carroll Institute, the process often includes:

• Eliminate triggers: Identify and remove inflammatory foods, environmental toxins, and infections.
• Reinoculate: Support microbial balance with prebiotics, probiotics, and fermented foods.
• Repair the gut lining: Nutrients like L-glutamine, zinc carnosine, and omega-3s help heal the intestinal barrier.
• Reduce inflammation: An anti-inflammatory, low-carb diet supports both digestive and brain health.
• Restore communication: Functional Neurology exercises can improve vagal tone and support better gut-brain signaling.

The Gut-Brain Connection in the ReCODE Protocol

In the Bredesen ReCODE Protocol, gut dysfunction plays a central role in both the inflammatory and metabolic subtypes of cognitive decline. When the gut is healed, inflammation decreases, nutrient absorption improves, and neurotransmitter balance is restored—all of which support memory, mood, and focus. Many patients notice improved clarity and energy within weeks of starting a gut repair plan.

Neuroplastic Healing Through the Gut-Brain Pathway

Once inflammation is reduced, the brain can begin to rebuild. Combining gut healing with Functional Neurology creates a powerful synergy: improved nutrient delivery and blood flow support the physical rewiring of neural pathways. Over time, this restores neuroplasticity—the brain’s natural ability to heal and adapt.

Healing Often Starts in the Gut

If you’re experiencing memory issues, brain fog, or unexplained fatigue, your gut health may hold the key. By identifying the underlying digestive imbalances and repairing the gut-brain connection, it’s possible to restore clarity, energy, and focus—naturally.

Book a Discovery Call with The Carroll Institute today to learn how Functional Medicine and Functional Neurology can help restore your gut-brain balance and protect your long-term cognitive health.

Sources

• Reversal of Cognitive Decline — NIH (2014)
• Beyond the brain: The gut microbiome and Alzheimer’s disease — NIH (2023)
• The Gut-Brain Axis in Alzheimer’s Disease — PubMed (2019)

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