The Daily Motivation Why 70% of Your Immune System Lives in Your Gut | Dr. Will Bulsiewicz
Jan 26, 2026
Dr. Will Bulsiewicz, gastroenterologist and author who studies the gut microbiome, unpacks how trillions of microbes shape your biology. He explores why 70% of immunity is located in the gut lining. He describes the fragile single-cell gut barrier, how permeability sparks constant immune activation, and how lifestyle factors leave fingerprints on your microbiome.
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Microbes Dominate Your Biological Blueprint
- Your gut microbiome contains ~38 trillion microbes and outnumbers human cells, shaping much of your biology.
- Will Bulsiewicz says the microbiome's genes make up roughly 99.5% of the genetic code influencing you.
Improve Daily Habits To Heal Your Microbiome
- Your microbiome reflects lifestyle choices like diet, sleep, exercise, relationships, and past trauma.
- Will Bulsiewicz implies improving these daily factors will positively reshape your gut community.
Most Immunity Lives In The Gut Lining
- About 70% of the immune system resides in the gut lining, right next to the microbiome.
- Will Bulsiewicz connects this proximity to why gut health directly affects whole-body inflammation.