Episode 22: Understanding the Gut-Brain Connection with Professor John Cryan

Your Gut Has Its Own Brain: The enteric nervous system contains more nerve cells than your spinal cord. This "second brain" sends signals directly to your brain via the vagus nerve, influencing how you feel moment to moment.

Three Pathways Link Gut to Brain: Gut bacteria communicate with the brain through metabolites that cross the blood-brain barrier, immune cells that signal to the brain, and hormones including GLP-1.

Your Microbiome Follows a Daily Rhythm: UCC research revealed that the gut microbiome shifts across the day with circadian rhythms. When the microbiome was depleted, normal daily stress regulation collapsed entirely — suggesting when you eat may matter as much as what.

Stress Reshapes Your Gut — And Vice Versa: Chronic stress alters gut bacteria composition, and those altered bacteria amplify the stress response. Feeding stressed students a diet rich in fibre and fermented foods dampened their stress response.

Parkinson's May Begin in the Gut: In many cases, gut symptoms like constipation appear years before brain symptoms. Pathological changes may travel from the gut to the brain via the vagus nerve, opening new avenues for early detection.

Social Behaviour Depends on Gut Microbes: Mice without gut microbes lose interest in social interaction entirely. When Prof. Cryan's team transplanted microbes from social anxiety patients into healthy mice, those mice developed elements of social anxiety — a causal link.

Most Commercial Probiotics Are Untested: The majority of probiotic products have never been tested for clinical benefit, and some don't survive stomach acid. Always ask whether the specific strain has published evidence behind it.