Biohacker Bryan Johnson reveals he has autoimmune disease that leaves 'stomach eating itself'

Bryan Johnson has revealed he is now living with an autoimmune disease, in a health update that has surprised followers given how closely he monitors almost every part of his body.

The 48-year-old tech entrepreneur has become one of the internet’s best-known biohackers through his extreme Blueprint project, which sees him spend millions trying to slow down ageing and track his body in unusually precise detail.

Johnson regularly shares updates about his sleep, diet, fitness, supplements and biological age, with his methods often sparking online debate — like never sharing a bed with his partner,or revealing food that will ‘change your life’.

However, his latest post on X (formerly Twitter) struck a very different tone, as the longevity enthusiast explained that one important issue had still managed to go unnoticed for years, even with so many tests already watching his health.

The condition Johnson says he has been diagnosed with is Autoimmune Gastritis, also known as AIG.

In said X post, Johnson summed it up with the shocking line: “My stomach is eating itself.”

AIG is a chronic autoimmune condition where the immune system attacks cells in the stomach lining. Those cells are responsible for producing stomach acid and intrinsic factor, which the body needs in order to absorb vitamin B12 — a nutrient that’s important for keeping both blood cells and nerves healthy.

As the condition progresses, it can cause nutrient deficiencies, anaemia and, over a longer period of time, an increased risk of certain stomach cancers.

Johnson wrote: “I just discovered it in May,” adding: “I'm unsure how long I've had it. AIG causes irreversible damage: nutritional deficiency, anemia, and over a long horizon, elevated cancer risk.”

The biohacker explained that he had been diagnosed with hypothyroidism when he was 21 through a routine blood test, allowing him to manage that issue with medication.

However, he said another autoimmune process was developing without obvious symptoms.

Johnson wrote: “What I didn’t know was that something else was going on inside my body: my stomach had begun attacking itself. But there was no routine test to find out and I didn’t have any symptoms.”

One of the main clues, according to Johnson, was his iron levels.

He explained: “For 11 years, I’ve had low ferritin, without anemia. We continually tried to raise my iron levels with food and supplementation but nothing would work”.

Johnson explained that because his haemoglobin and haematocrit levels appeared normal, the low ferritin was easy to overlook.

He has since said he corrected his iron deficiency with an IV infusion, but appears to be aiming for more than simply managing the condition.

In the post, Johnson called on specialists to get in touch, writing: “If you're working on autoimmune gastritis, antigen-specific tolerance, regulatory T cells, or CAAR-T for organ-specific autoimmunity, please reach out.”