• Billy Bob Thornton has type AB-negative blood, which affects fewer than 1% of people worldwide.
• The condition means fewer digestive enzymes and lifelong allergies to wheat, dairy, meat, and shellfish.
• Thornton opened up on the Howie Mandel Does Stuff podcast, revealing a typical day of blueberries and gluten-free snacks.
• He discovered his blood type in 1980 and has described himself for years as “a vegan who cheats.”
• The Landman star, who turned 70 this year, also has a history of OCD, an eating disorder, and other health challenges.

Billy Bob Thornton has spent decades figuring out what his body will and won’t tolerate — and it turns out, the answer has been in his blood the whole time.

The Landman star, 70, opened up during a recent episode of the Howie Mandel Does Stuff podcast about the strict dietary life that comes with having type AB-negative blood, one of the rarest blood types on the planet. “I have type AB negative blood, which is the rarest type in the world,” Thornton told host Howie Mandel. “It’s like less than 1% of the population of the world has it.”

The condition, he explained, comes with a key biological catch: fewer digestive enzymes. That deficiency is the root of a lifetime of food sensitivities — allergies to wheat and dairy, a need to avoid shellfish, and a hard pass on pork and beef. Thornton discovered his blood type back in 1980, but the symptoms had been there his whole life. He just didn’t know what was causing them.

“When I was a kid, you know, I grew up in Arkansas and East Texas, and I ate everything,” he said. “I just assumed everybody felt like s— after they ate. I didn’t know.”

What a Typical Day Looks Like on the Billy Bob Thornton Diet

When Mandel asked what Thornton had actually eaten that day, the answer was pretty spartan: a bowl of blueberries and a decaf coffee. Looking ahead to later in the day, he was optimistic. “I’m going to have some gluten-free chips with some dairy-free cream cheese,” he said. “So I’m really looking forward to that.”

Working within those constraints takes creativity — and sometimes a willingness to improvise with whatever’s in the green room. Thornton recalled being at a Landman event where the spread was essentially off-limits: one tray of salami and prosciutto, another full of crackers he couldn’t touch. “Normally in these green rooms, they got a spread. I mean, you can usually find something, you know?”

Then he spotted a bowl of red and white grapes. And some spicy Dijon mustard. He took a chance.

“I’m like, ‘Oh, OK, so I’ll be bored as hell with this,'” he said of the grape. “And then I saw some spicy Dijon mustard and thought, ‘I wonder…'” The result? He called it “one of the best things I’ve ever had in my lifetime. So now it’s become a thing for me.”

Thornton has long described himself as “a vegan who cheats” — a label he put on himself during a 2020 appearance on the Mental Amanda podcast, where he admitted to occasionally breaking for salmon or halibut, or the pull of good Texas barbecue. The AB-negative blood type gives the phrase a whole new layer of meaning.

A Long History With His Health

This isn’t the first time Thornton has had to reckon with his body in a serious way. In 1998, while filming U Turn, he dropped 59 pounds — surviving largely on canned tuna and Twizzlers to look gaunt for the role — and developed an eating disorder. Two years later, he was rushed to Cedars-Sinai Hospital in Los Angeles following a viral infection, which quickly became tabloid fodder with rumors flying that he’d had a heart attack or could only eat orange-colored foods.

He’s also been open about his OCD diagnosis, which he’s connected to a difficult childhood marked by abuse. In a 2004 interview with Ann Curry, he described the hypervigilance that defined his early years: “I would hear the car pull in the driveway around 4 o’clock usually, and I would, in my head, I would say if I can count to a hundred five times before I hear the car come in the driveway, everything’s going to be okay.” The constant mental calculation, he said, is emotionally and physically exhausting.

Now, at 70 — a milestone he’s spoken about with both pride and perspective — Thornton seems to have found a kind of peace with all of it. He’s talked about the unexpected gift of aging in Hollywood: the respect that comes with it, the wisdom people project onto you. “We’ve all seen each other get older,” he said, “and when I see that wisdom and see the respect that people have for them, it just kind of makes everything melt away somehow.”

Landman is set to begin filming its third season in August, which means more green rooms, more questionable spreads, and probably a lot more creative grape-and-mustard situations ahead.

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