What if I told you there's an organ in your body with more cells than the Milky Way has stars—and most doctors barely think about it? In this episode of Extend, I sit down with Dr. Zain Kassam, a gastroenterologist turned microbiome researcher who's pioneering how we understand the trillions of organisms living in and on us.

We dive into why your gut bacteria aren't just bystanders—they're actively producing molecules that affect your mood, metabolism, immune system, and even longevity. We also explore the gut-brain connection, why not all probiotics are created equal, and how the microbiome influences everything from depression to skin health.

Dr. Zain Kassam is a gastroenterologist, microbiome researcher, and Chief Medical Officer at Seed Health. He trained at McMaster University, Harvard, and MIT, where he pioneered clinical applications of microbiome science. He's led groundbreaking research on fecal transplants and develops evidence-based probiotic therapies.

We Also Discuss:

The Microbiome Revolution: From Forgotten to Life-Saving
Why Your Gut Has More Cells Than the Milky Way Has Stars
How Gut Bacteria Control Your Brain and Mood
The Butyrate Connection: Your Microbiome's Master Molecule
Why Most Probiotics Are Marketing Hype (And How to Choose Better)
The 4D Framework: Diversity, Delivery, Do-Gooders, and Data
Microbiome Testing: Crystal Ball or Expensive Guesswork?
From C. Diff to Cancer: When Gut Health Becomes Life or Death
The GLP-1 Secret: How Your Gut Makes Its Own Ozempic
Post-Antibiotic Recovery: Rebuilding After the Nuclear Bomb

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Learn more about Dr. Shah:

Website: https://www.drshah.com/

Clinic: https://www.next-health.com/

Instagram: https://www.instagram.com/darshanshahmd/

Learn more about Dr. Zain Kassam:

X: https://x.com/DrZainSays/

Instagram: https://www.instagram.com/seed/

Get 25% off DS-01 with code EXTEND25 at Seed.com

Avivah Wittenberg-Cox and I will talk about the 4-Quarter life and living to 100… or not?!