Dr. Karan Rajan on Fiber Fermentation, Sodium Myths, and What Your Poop Reveals About Disease Risk
Your poop is more predictive than almost any other health signal, and you are flushing that data away every single day without a second look.
Host Dave Asprey sits down with Dr. Karan Rajan, a practicing NHS gastrointestinal surgeon, best-selling author, and Chief Science Officer at Throne, who has built a following of over 12 million people by making gut science accessible and actionable. He has spent his career removing colon cancers, treating digestive disease, and now studies how gut bacteria drive nearly every system in the body, from hormone metabolism to brain optimization.
They break down why fibermaxxing can backfire without the right mix of fast, medium, and slow fermenting fibers, and why generic "eat more fiber" advice ignores what your gut bacteria actually need. The conversation covers protein absorption limits and how much your body can really use, the truth about saturated fat and metabolism, and why the sodium-to-potassium ratio matters more than sodium alone. They also dig into fasting and the gut’s natural cleaning cycle, the estrobolome and testobolome and their role in hormone balance and longevity, and how AI is starting to reshape personalized health data, supplements, and functional medicine. Dr. Rajan shares some of the strangest objects he has surgically removed from patients, and explains what your poop’s color, shape, and consistency reveal about liver function, inflammation, and disease risk long before symptoms show up anywhere else.
This is essential listening for anyone serious about biohacking, gut health, human performance, longevity, mitochondria function, nootropics, ketosis, carnivore and fiber-based diets, sleep optimization, anti-aging, and hacking your metabolism from the inside out.
You’ll Learn:
-Why fibermaxxing can cause bloating instead of better gut health
-The real difference between fast, medium, and slow fermenting fibers
-How much protein your gut can actually absorb and digest
-Why low sodium may be more dangerous than high sodium for most people
-How fasting triggers your gut’s natural cleaning cycle, the migrating motor complex
-What your poop’s color and consistency can reveal about liver and metabolic health
-How gut bacteria influence hormone metabolism through the estrobolome and testobolome
-Where AI and functional medicine are headed in personalized gut health tracking
Resources:
• Dr. Karan’s Newsletter: https://drkaran.kit.com
• Learn more about Throne – https://www.thronescience.com/
• Check Out Dr. Karan’s YouTube: https://www.youtube.com/c/DrKaran
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Thank you to our sponsors!
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– Kenetik | Instead of pushing your system harder, Kenetik feeds your brain the ketones it craves to fuel calm clarity and steady focus. Go to drinkkenetik.com/DAVE and use code DAVE for a discount.
Timestamps:
00:00 – Trailer
00:55 – Meet Dr. Karan Rajan
04:04 – Kellogg’s History & Farts
11:53 – Throne Poop Tracking
19:35 – Poop Colors & Wild Stories
28:02 – Worst Foods & Saturated Fat
36:26 – Fiber Fermentation Geography
46:57 – Sodium & Salt Myths
59:03 – Keto, Carnivore & Fasting
01:04:45 – AI, Misinformation & Closing
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