Bryan Johnson, the life extension guru who chronicles his efforts to reduce his “biological age,” says he has Autoimmune Gastritis (AIG), an incurable disease that he only discovered he had in May. Johnson wrote on X that he doesn’t know how long he’s actually had AIG, which causes B12 and iron deficiency, leading to anemia. But he’s vowing to work on “experimental approaches” to find a cure and has asked anyone working on the disease to reach out. Johnson, who’s 48 years old and constantly chronicling his efforts to maximize his health online, blamed his AIG on unhealthy foods he ate in his youth, along with the stress that came with being a father. “As a kid, I ate sugar cereal, drank sugary soda, and gobbled down fast food. I had a few healthy years in my early 20s but then became a young father of three and began building a business,” wrote Johnson. “Juggling that stress and grind, I let my health slip and gained 40 lbs. Within a few years I’d fallen into a deep, chronic depression. Somewhere in that timeline, my body began developing an autoimmune process affecting my thyroid and then my stomach lining,” Johnson continued.
Bad news #1: I have an autoimmune disease. My stomach is eating itself. Bad news #2: 2–5% of people have this, too. Likely more, because it hides. Good news: I'm going to try and solve it. Will share all. As a kid, I ate sugar cereal, drank sugary soda, and gobbled down… pic.twitter.com/EbJ8a916uS — Bryan Johnson (@bryan_johnson) June 30, 2026 Johnson takes dozens of pills per day and was featured in a 2024 Netflix documentary called Don’t Die: The Man Who Wants to Live Forever. He founded the company Braintree, which bought the payments app Venmo in 2012. Johnson then sold Braintree to PayPal for $800 million.
