Bryan Johnson fears the autoimmune condition he recently revealed “would be much worse” if not for the painstaking attention he’s been paying to his health, the biohacker told The Independent on Tuesday.
In a brief email exchange, the 48-year-old tech entrepreneur also said his May diagnosis of autoimmune gastritis — which he recently revealed to the public — was likely tied to an earlier diagnosis of autoimmune hypothyroidism at age 21, “so this has been part of my body for 27 years.”
“Had I not taken care of my body during the past five years, the situation would be much worse so I am very grateful to have been focused on health,” he wrote.
Johnson’s email was sent around the same time he posted an online photo that shows him receiving an infusion of what he described as 1,000 mg of Monoferric, an intravenous treatment for adults with iron deficiency anemia.
“I had low iron for 11 years,” he wrote on X. “I’ve finally boosted it back to healthy levels.”
Johnson blamed his iron deficiency on autoimmune gastritis, saying of the condition, “With AIG, my stomach doesn’t make enough acid to absorb iron.”
Earlier, Johnson pushed back against critics who’ve blamed his condition on the extreme, $2 million-a-year “Don’t Die” regimen he’s adopted to defy aging and extend his life.
In a series of lengthy social media posts over the past week, Johnson defiantly defended his unconventional lifestyle choices, saying he’s trying to “break the spell” of unhealthy traditions like “Thanksgiving debauchery, New Year drunkenness, Halloween indulgence, the wedding open bar, the treat, splurge and cheat day.”
“The anesthesia only works if everyone does it together. One abstainer reveals to the room that they are drunk,” he wrote on X. “This is the source of the anger. It’s not my decisions. It’s their reflection in the mirror.”
Johnson —whose anti-aging efforts include hyperbaric oxygen therapy and being infused with his son’s blood plasma — insisted his comments weren’t “an attack on any person, lifestyle choice or health practice.”
“I’m agnostic to what you do and why you do it,” he wrote.
But the subject of the 2025 Netflix documentary Don’t Die: The Man Who Wants to Live Forever also claimed his critics were “likely to have one or several undiagnosed health issues,” saying most people mistook “the absence of diagnosis” for “the presence of health.”
“For those who do not routinely measure their health, that ignorance manifests a false sense of physiological superiority,” he wrote.
Johnson also rejected online arguments he summarized as “meat will remedy my autoimmune gastritis,” “sunlight is the cure” and “the culprit is the food I consume.”
“These are unlikely,” he wrote.
On June 30, Johnson told his 1.6 million followers he had learned a month earlier that his stomach was “eating itself” as a result of autoimmune gastritis.
The incurable condition occurs when a person’s immune system attacks the lining of their stomach — raising the risk of cancer — and affects an estimated 0.5 to 2 percent of the U.S. population, according to the Cleveland Clinic.
“I’m going to try and solve it. Will share all,” he vowed.
He wrote that for years, he had been unaware he was dealing with the disease, but said that it was likely caused by his diet of fast food and sugary beverages in the years before he started biohacking his health routine, which included changes to his diet and sleep habits.
“As a kid, I ate sugar cereal, drank sugary soda, and gobbled down fast food,” Johnson said. “I had a few healthy years in my early 20s but then became a young father of three and began building a business. 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.”
In one of his follow-up posts, Johnson said that his “autoimmune profile began at a young age when I was regularly eating red meat and was in the sun for multiple hours a day” and that he was “diagnosed with autoimmune thyroid disease when I was 21 years old.”
“My body’s genetic and immunological architecture made a mistake decades ago, failing to distinguish between my own tissues and external threats,” he wrote. “Trying to cure a decades old, genetically driven, antigen specific immune failure by switching to a meat diet or getting sunlight is like trying to fix a corrupted line of software code by altering the temperature of the room.”
Johnson also said he was being “told hundreds of times a day that I need to live a little. That I’m so busy trying to not die that I’ve forgotten to live.”
“I don’t intend to live a little. I intend to live more than any human who has yet lived and invite you to join me,” he wrote.
