Former Kernel CEO and self-proclaimed ‘Biohacker,’ Bryan Johnson has spent years trying to slow aging through meticulous health tracking, experimental therapies, and a multimillion-dollar wellness regimen. “I have an autoimmune disease. My stomach is eating itself,” Johnson wrote on X, adding he plans to try to solve it. The diagnosis: autoimmune gastritis, a chronic condition in which the immune system destroys the stomach’s acid-producing cells.
The 48-year-old founded the longevity brand, and what he calls a religion, Don’t Die, is also known for taking extreme measures, such as receiving blood plasma transfusions from his teenage son. His diagnosis surfaced after a routine colonoscopy at age 48, despite years of obsessive biological monitoring. Experts say the case is drawing welcome attention to a disease that’s notoriously difficult to catch.
The Experts’ Views and Findings
Toby Cornish, a gastrointestinal pathologist at the Medical College of Wisconsin, said Johnson’s diagnosis may help raise awareness of a condition gastroenterologists frequently overlook.“Gastroenterologists should really be sampling more ‘normal’-appearing stomachs in patients with a history of iron deficiency that’s been treated, because many of those patients will actually turn out to have autoimmune gastritis,” he said.
Johnson took note of his frequently low ferritin, a protein reflecting iron stores, even though standard anemia markers were normal, making the problem easy to dismiss. Mimi Chang Tan, assistant professor of gastroenterology at Baylor College of Medicine, said the disease “is notoriously insidious and frequently remains silent for decades, with symptoms often presenting outside of the gastrointestinal tract as fatigue, weakness, or neurological issues.”
A definitive diagnosis requires an upper endoscopy with biopsies, and anyone with unexplained low ferritin warrants screening for far more common causes, too, like colorectal cancer and H. pylori infection, according to Tan.
Demystifying the Condition — Autoimmune Gastritis
Autoimmune gastritis occurs when the immune system attacks the stomach’s acid-producing cells, eventually impairing iron and, later, B12 absorption, according to Cleveland Clinic. It’s distinct from the more common environmental form of atrophic gastritis, typically driven by H. pylori bacteria rather than the immune system itself.
- Prevalence: Estimated to affect around 4% of people worldwide, though Cleveland Clinic puts the U.S. autoimmune form at roughly 0.5% to 2%, which is likely undercounted given how often it’s missed.
- Risk factors: Being female, family history of the condition, certain genetic mutations, and other autoimmune diseases like Hashimoto’s, Graves’ disease, Type 1 diabetes, or Addison’s disease all raise the odds.
- Possible cause in Johnson’s case: The exact cause isn’t known, but likely involves genetic factors, environmental triggers, and chronic inflammation. Johnson speculated a link to his childhood fast-food diet, but experts called that theory “highly speculative,” pointing instead to his existing autoimmune thyroid disease as a statistical risk factor, even though one doesn’t directly cause the other.
- Serious complications: Left unaddressed, the condition can cause pernicious anemia and nerve damage from B12 deficiency, and patients face meaningfully higher risk of stomach cancer and neuroendocrine tumors, which form as the stomach overproduces the hormone gastrin trying to restore lost acid production.
Maybe Trying to ‘Live Forever’ Won’t Be Worth It
Jennifer Dowd, a professor of demography and population health at the University of Oxford, said Johnson’s diagnosis is a reminder that “you really can’t biohack your way completely out of disease or death,” no matter how much someone optimizes their health. That’s notable given Johnson’s image as, in his own words, “the most biologically measured person alive,” someone who has spent millions tracking nearly every measurable marker of his body.
His case is worth learning from precisely because it shows the limits of extreme self-optimization. Despite obsessive monitoring, Johnson’s diagnosis was nearly missed, partly because he was overdue for a routine colonoscopy, and partly because the disease often hides behind normal-looking bloodwork.
The Human Body Should Be Treated With Respect
There’s currentlyno cure, and Cleveland Clinic notes reducing risk of the autoimmune form isn’t really possible, only earlier detection and ongoing management.
That cuts against the premise of biohacking as a path to indefinite life extension: supplements, laser caps, and blood transfusions can’t substitute for basic, unglamorous preventive care, like getting a colonoscopy on schedule.
For anyone chasing longevity trends, Johnson’s experience is a useful check on the idea that money and self-tracking can outrun biology altogether, but not one that should be followed.
