EP 1436
1436. If Your Poop Looks Like This, Pay Attention | Gut Surgeon Explains
Host Dave Asprey sits down with Dr. Karan Rajan, 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, why the history of Kellogg’s cornflakes reveals how flawed thinking about the gut shaped a century of bad health advice, why more than 70 percent of your farts are actually produced by bacteria and not by you, how a camera and sonography system can track your poop, pee, and prostate health well enough to catch problems before symptoms appear, the strangest objects Dr. Rajan has surgically removed from patients including a shower head that perforated a man’s colon, what poop color actually reveals about liver function, bile flow, and internal bleeding, why the fibermaxxing trend gets fiber wrong and why fermentation speed and location in the colon matter more than soluble versus insoluble labels, why inulin supplements can cause serious bloating and even damage the gut lining, the real science behind saturated fat, ghee, and why stearic acid may protect against fatty liver disease, why low sodium intake may be more dangerous than high sodium for most people and what the sodium to potassium ratio actually controls, the estrobolome and testobolome and how gut bacteria influence hormone metabolism and fertility, Dr. Rajan’s own journey through keto and carnivore diets before returning to a fiber rich, fermented food approach rooted in his South Indian background, and why fasting activates the gut’s natural cleaning cycle known as the migrating motor complex. Essential listening for anyone serious about biohacking, gut health, fiber science, longevity, and understanding what your body is trying to tell you every single day.
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In this Episode of The Human Upgrade™...
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
Keywords: Karan Rajan, gut surgeon, fibermaxxing, gut microbiome, Bristol stool chart, poop health, Throne, fermentation geography, soluble fiber, insoluble fiber, prebiotics, inulin, oxalates, estrobolome, testobolome, migrating motor complex, sodium potassium ratio, saturated fat, ghee, collagen, protein absorption, keto, carnivore, fasting, gut bacteria, flatulence science
Resources:
- Dr. Karan’s Newsletter: https://drkaran.kit.com
- Check Out Dr. Karan’s YouTube: https://www.youtube.com/c/DrKaran
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"Fasting switches on the Roomba. This biological Roomba that works its way through the gut."
Karan Rajan
00:00 – Trailer
A quick preview of the episode’s biggest hooks, from surgically removed objects to the surprising science of your poop.
00:55 – Meet Dr. Karan Rajan
Dr. Karan Rajan, NHS gut surgeon and 12 million follower health educator, joins the show to talk about his path from removing colon cancers to becoming obsessed with the microbiome.
04:04 – Kellogg’s History & Farts
The disturbing history of Dr. Kellogg’s anti-libido cornflakes and enema obsession leads into why more than 70 percent of your farts are actually produced by bacteria, not you.
11:53 – Throne Poop Tracking
Dr. Rajan explains how Throne’s camera and sonography system tracks Bristol stool scale, toilet time, urine flow, and hydration to catch deviations from your personal baseline.
19:35 – Poop Colors & Wild Stories
What black, red, green, and white poop actually signal about bleeding, infection, and bile flow, followed by the strangest objects Dr. Rajan has surgically removed from patients, including a shower head that perforated a man’s colon.
28:02 – Worst Foods & Saturated Fat
Why the real danger to gut health is a dietary pattern low in fiber and high in saturated fat and salt, and a debate over whether all saturated fats, including ghee, deserve the same reputation.
36:26 – Fiber Fermentation Geography
Dr. Rajan introduces fermentation geography, mapping how fast, medium, and slow fermenting fibers feed different bacteria across the colon, and why inulin supplements can cause serious bloating.
46:57 – Sodium & Salt Myths
A deep dive into research showing low sodium can be more dangerous than high sodium for most people, and why the sodium to potassium ratio matters more than salt intake alone.
59:03 – Keto, Carnivore & Fasting
Both guests share their personal histories with keto and carnivore diets, the health issues that led them back to fiber, and how fasting triggers the gut’s natural cleaning cycle.
01:04:45 – AI, Misinformation & Closing
A conversation on where AI is headed in personalized health data, the risks of training models on unreliable research, and closing thoughts on staying open to changing your mind.
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