The second brain

The second brain

What drives someone to seek a healthier mind by looking beyond the brain itself? This episode of *All In The Mind* takes that question seriously by turning attention to the gut, often dubbed "our second brain". Host Lynne Malcolm brings together neurologist Dr David Perlmutter and psychiatrist Dr James Greenblatt to talk about the surprising ways gut bacteria can influence mood, behaviour and long‑term brain health.

Perlmutter points out that "inflammation is the cornerstone of virtually every degenerative condition" and argues that this inflammation is strongly shaped by the balance of good and bad bacteria in the gut. Greenblatt breaks down what the microbiome actually is and shares how psychiatric practice is beginning to factor in digestive health.

He explains that there are more bacterial cells in the gut than cells in the rest of the body, and that this microbial community can affect appetite, mood and conditions such as autism, ADHD and obsessive compulsive disorder. His case story of Mary, a teenager with severe OCD whose condition eased after targeted high‑dose probiotics, gives this science a very human face.

You’ll hear clear explanations of how serotonin is mostly made in the gut, how the vagus nerve physically and chemically links gut and brain, and why an "overly clean environment" and heavy antibiotic use may be backfiring on mental health. Perlmutter is optimistic about future treatments based on shaping the microbiome, but he repeatedly stresses that research is young and that any new approach has to follow the principle of "above all, do no harm".

For anyone curious about why diet, birth method, antibiotics and fermented foods might matter to mood and cognition, this episode offers plenty to think about without overhyping the evidence. It’s a smart listen if you’ve ever wondered whether looking after your gut could be one more way to look after your mind too.