St. Louis, MO — September 28, 2026 · Book launch
The third volume of The Brain reverses the organ hierarchy most medicine teaches: the gut’s nervous system came first, and a starved, permeable, inflamed first brain cannot produce a calm, regulated second one.
Dr. Gurpreet Singh Padda, MD, MBA, MHP, has released The Angry Gut: The First Brain: Older Than Thought, and Still in Charge, the third volume in his series The Brain and the one he places upstream of the other two. Written with coauthor Ami Michelle Grimes, the 492-page book reverses the organ hierarchy most medicine teaches. The enteric nervous system arrived first in evolutionary time, the book argues, and the processor inside the skull is the later addition, tethered to the gut by the vagus nerve and interpreting a biological reality that was settled in the bowel before it ever reached the head.
That inversion is not a metaphor in this book. It is the organizing claim, and it carries a clinical consequence Dr. Padda states early: a starved, permeable, inflamed first brain cannot physically produce a calm, regulated second one. Treating the head while the bowel burns, he writes, is masking a fire alarm.
The method, demonstrated on a number everyone repeats
The Angry Gut is built on a habit that shows up in its opening chapters and never lets go: when a famous figure and a measured figure disagree, the book prints the measured one and shows its work.
The intestinal surface is the size of a tennis court. Every clinician has said it. The researchers who went to check opened their paper by quoting the textbook claim of 260 to 300 square meters, then measured it by intubation, radiology, and microscopy and found a mean total mucosal surface of roughly 32 square meters. Their own replacement metaphor was not a tennis lawn but half a badminton court (Helander & Fandriks, 2014).
“The folklore was wrong by an order of magnitude, and the real number is still astonishing,” Dr. Padda said. “That is the whole argument for checking. A number that survives being checked is worth more than ten that were never checked. A figure printed in every textbook has usually been checked in none of them.”
Three claims the book declines to repeat
- That the vagus nerve is 80 to 90 percent afferent. The current literature hangs that ratio on two references, one of them a rat study whose authors concluded the opposite of what they are cited for (Prechtl & Powley, 1990). No modern study has directly counted afferent against efferent fibers in a human vagus. The book prints what has actually been measured in human tissue instead: a cervical vagus carrying 51,288 plus or minus 10,225 fibers, an abdominal vagus carrying 28,714 plus or minus 15,996, and 94 percent of those abdominal fibers unmyelinated.
- That gut serotonin explains mood. Gut-derived serotonin does not cross the blood-brain barrier; the brain manufactures its own from local pools (Chen et al., 2021). The book keeps the gut-brain link and relocates it to mechanisms that survive scrutiny, including vagal afferent signaling and tryptophan availability.
- That a positive small-intestinal bacterial overgrowth test settles anything. The field’s own consensus body states that current small bowel culture techniques are not satisfactory for the assessment of SIBO (Rezaie et al., 2017), and the American Gastroenterological Association is explicit that there is insufficient evidence to support inflammatory markers such as fecal calprotectin for detecting it (Quigley et al., 2020).
What the 33 chapters cover
Chapter 0 establishes the evolutionary premise before the argument begins: primordial organisms with essentially digestive tracts, and a human gut as the creature’s outer surface folded inward to meet the environment. From there, the book moves through the acid-suppression economy and what it costs absorption, the vagal highway, intestinal permeability, the fatty liver, intrinsic factor failure and B12, collagen, bile acids, vitamin D, the disc microbiome, trauma as a biological blueprint, the enterocyte that is replaced every three to five days and what it is being asked to rebuild itself from, the artificial food supply, sleep, glyphosate, the narcotic bowel, the hypochlorhydria myth, histamine, and the nicotine paradox.
Chapters end with a code the reader can scan to pull the matching technical supplement, free, written for the appointment rather than for the shelf and published at theangrygut.com one chapter at a time. Numbers appear with the values their papers reported, the population stated, and thin evidence labeled thin rather than sold as solid. There is no detox, no protocol to buy, and nothing to sign up for.
The whole book has also been filmed. Thirty-three episodes, one per chapter, are published on the Regen.MD channel and mirrored for the Padda Institute audience.
“Patients arrive having been told their labs are normal and their problem is stress,” Dr. Padda said. “Then you look at what they are actually absorbing, and at what their first brain has been marinating in for twenty years, and the anxiety stops being mysterious. I am not asking anyone to take that on faith. Every chapter hands you the paper.”
Availability
The Angry Gut: The First Brain: Older Than Thought, and Still in Charge by Dr. Gurpreet Singh Padda, MD, MBA, MHP, and Ami Michelle Grimes is available now on Amazon in Kindle and paperback editions. Paperback ISBN 978-0-9832058-2-1. Published by Nectar Media Group. 492 pages, 33 chapters. Book and technical supplements: theangrygut.com.
It is the third volume in The Brain, following The Starved Brain and The Pained Brain, and preceding The Dopamine Brain and the forthcoming The Humbled Brain.
About Dr. Gurpreet Singh Padda, MD, MBA, MHP
Dr. Gurpreet Singh Padda, MD, MBA, MHP is an interventional pain physician, anesthesiologist, and addiction medicine specialist in St. Louis, board-certified in anesthesiology, pain medicine, interventional pain management, addiction medicine, and obesity medicine, and a certified Metabolic Health Practitioner. He has led the Center for Interventional Pain Management since 2001 and directed the Center for Regenerative Medicine since 2004. A former Assistant Professor of Anesthesiology and Pediatrics, he has delivered ASIPP keynotes on metainflammation and the hedonic treadmill and spoken on metabolic health for LowCarbUSA and the Society of Metabolic Health Practitioners.
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