Four percent. That is the share of people worldwide estimated to have autoimmune gastritis, the stomach disease Bryan Johnson says he now has. The tech entrepreneur, 48, announced it on X with a flat sentence: “I have an autoimmune disease. My stomach is eating itself.” He added that he intends to “try and solve it.”
In autoimmune gastritis, antibodies wipe out the acid-producing cells in the stomach lining. Iron absorption suffers first. Over time, vitamin B12 runs short, which can bring anemia and nerve problems. The disease is not fatal on its own, but it carries a higher risk of stomach cancer.
It is also easy to miss. Mimi Chang Tan, an assistant professor of gastroenterology at Baylor College of Medicine, described it as “notoriously insidious,” often silent for decades, with symptoms such as fatigue or weakness that seem unrelated to the gut. The 4% figure may undercount, since gastroenterologists often fail to recognize the disease.
How Johnson’s case surfaced
His first clue was ferritin, the blood protein that shows how much iron the body stores. Johnson’s level stayed low year after year. His hemoglobin and hematocrit, the numbers used to diagnose anemia, looked normal, so the problem was easy to wave off. A definitive answer needed an upper endoscopy with biopsies, and those confirmed autoimmune gastritis.
Johnson also described the colonoscopy he had while hunting for an explanation: “I was 48 years old and overdue.” The U.S. Preventive Services Task Force recommends starting at 45. Johnson calls himself “the most biologically measured person ever” and says he spent $2 million on medical treatments in 2023 alone. He did not respond to a request for comment on the delay. Toby Cornish, a gastrointestinal pathologist at the Medical College of Wisconsin, noted that the guidelines only dropped the starting age from 50 to 45 in 2021. “Sometimes people would get lost in the shuffle,” he said.
What causes it, and what helps
Johnson has floated a link between his childhood diet of fast food, sugary cereal and soda, and later a 40-pound weight gain, and the disease. Cornish was blunt about it. “I would call that highly speculative,” he said. Tan said the cause is not known and may combine genes, environmental triggers and chronic inflammation. People with autoimmune thyroid disease, as Johnson has, are more likely to be diagnosed with it, though neither causes the other.
Treatment is thin. “We don’t really have good treatments for it,” Cornish said. Patients take iron by mouth or by IV and get monitored for cancer. They are 13 times more likely to develop neuroendocrine tumors, and the goal is to catch them early enough for removal through an endoscope instead of surgery. They also face a higher risk of adenocarcinoma.
Cornish explained why the tumors turn up so often. With too little acid, the stomach keeps releasing gastrin to raise it. Without parietal cells, acid never rises, so gastrin keeps flowing, and enough of it eventually forms tumors. Found early, the outlook tends to be good.
Johnson wrote that standard care “concedes defeat.” His team is looking at experimental options, including CAR-T therapy, a personalized gene-based treatment that has shown promise in several autoimmune diseases. Cornish said it is not well studied for this condition. He called it probably the best line of investigation toward a cure, but “still very early.”
Jennifer Dowd, a professor of demography and population health at the University of Oxford, said Johnson’s announcement shows that “you really can’t biohack your way completely out of disease or death.” Cornish sees a different use for the news: more doctors might biopsy stomachs that look normal in patients with a history of treated iron deficiency, “because many of those patients will actually turn out to have autoimmune gastritis.”
Johnson, who runs the supplement company Blueprint and calls his Don’t Die project a religion, said the diagnosis came as a relief. “You want to know if there is a problem with your body,” he wrote on X. “Ignoring it doesn’t make it better. Delay just makes it harder, costlier, and riskier.”
Sources
- Bryan Johnson’s chronic disease is notoriously difficult to diagnose
- Bryan Johnson Diagnosed with Autoimmune Gastritis
