Bryan Johnson is a technology businessman from the United States. On 7 July, he said he has autoimmune gastritis, a long-term illness that hurts the stomach lining. Johnson became famous for spending millions of dollars on health experiments to try to slow down ageing.

Autoimmune gastritis happens when the immune system, which usually protects the body, attacks healthy cells in the stomach by mistake. This damage can stop the stomach from making enough acid and stops the body from absorbing vitamin B12, which is important for healthy blood.

Johnson was diagnosed with this illness in May. As a result, he is now having regular blood tests and treatment for his condition. He hopes to find a way to stop the immune cells from hurting his stomach, but any new treatment will need more testing before it can be used.