A few years ago, Dr. Gregory Thomas thought he had finally found the Holy Grail of heart disease. And it was even found in a tomb.
He was studying the arteries of 3,000-year-old Egyptian mummies, and he thought this was finally it: a culture that would be free of heart disease. Heart disease couldn't be more than 3,000 years old, could it?
Man, he was disappointed.
"The mummies had a great deal of atherosclerosis in their peripheral arteries," says Thomas, who directs the MemorialCare Heart & Vascular Institute at Long Beach Memorial Medical Center in Long Beach, Calif. "So our assumption was that plaque in arteries was a universal part of aging."
In other words, no matter how much you exercise, how much kale you eat and how many cigarettes you avoid, heart disease is inevitable. Eventually everyone's arteries will harden up with some calcium plaque as they age, Thomas thought, increasing the risk of heart attacks and strokes.
Now a group of farmers in Bolivia have blown that theory out of the water, Thomas says.
The Tsimane are a native population in the Amazon who make a living by hunting, fishing, foraging and farming. The group has preserved their culture and language for thousands of years. And their way of life is incredibly good at protecting the heart, Thomas and his colleagues reported Friday in The Lancet.
Of Tsimane people over age 40, about 85 percent have no atherosclerosis. And nearly two-thirds over age 75 were apparently free of arterial plaque.
Compare that to Americans — who have exactly the opposite statistics. Nearly 85 percent of Americans over age 45 have atherosclerosis. And only 14 percent are free of the plaque.
That data means the heart of an 80-year-old Tsimane has the "vascular age" of an American in his or her mid-50s. And the Tsimane have officially dethroned Japanese women as the group of people with the healthiest hearts in the world, the study reports. The Tsimane now have the lowest levels of coronary artery disease ever recorded.
"I was just floored by the data," Thomas says. "The Tsimane have extraordinarily healthy hearts."
So what's their secret?
To figure that out, Thomas and his colleagues measured the amount of calcium deposited in the coronary arteries of more than 700 Tsimanes between age 40 and 94.
The team also measured other factors connected to heart disease, such as blood pressure, body-mass index, cholesterol levels and inflammation levels.
On the surface, it wasn't clearcut that the Tsimane's would have such remarkable heart health. Their risk factors for heart disease are a mixed bag.
The group has low blood pressure and low cholesterol, on average. But they have low levels of the "good" cholesterol and high levels of chronic inflammation, which has been linked to heart disease.
In terms of weight: None of the Tsimane are obese but about a quarter of adults qualify as "overweight," says Michael Gurven, an anthropologist at the University of California, Santa Barbara, who contributed to the study.
The average BMI was about 24, which is near the upper end of normal, with a BMI of 25 considered overweight. "So it's not that they are super-lean," Gurven says.
The Tsimane get a ton of exercise, Gurven says, but it's not really intense exercise.
"I think there's a general stereotype that if you're a hunter-gatherer and farmer, that you're exercising vigorously every day, like the equivalent of running a marathon, and that's not the case," Gurven says. "It's really just that they're not sedentary."
Instead the Tsimanes do a lot of walking — about 7 1/2 miles each day. And they're active for more than 90 percent of daylight hours. In contrast, Americans spend about half their waking hours sitting down.
And finally, there's diet. When you hear "hunter-gatherer," people often think of the meat-packed paleodiet. But the Tsimane diet couldn't be further from that.
More than 70 percent of their calories come from carbohydrates — ones that are packed with fiber, such as corn, cassava and plantains. The other 30 percent of the calories are split evenly between protein and fat. The Tsimane eat no transfat and very little simple sugars. In contrast, Americans still eat more than a gram of transfat each day and 22 teaspoons of extra sugar.
So in the end, what's the key to their superb heart health? The high-carb, low-fat diet? The abundance of low-level exercise? A relatively healthy weight?
Gurven says they don't know yet. But it's probably a combination.
"You know it's not exactly the answer people want to hear," Gurven says. "There's no silver bullet against heart disease."
But the findings also show that you don't have to go to extremes to boost your heart health. A little extra walking, a little less fat and a few pounds off your frame probably work in concert to cut your risk of heart disease.
DAVID GREENE, HOST:
A mystery in Bolivia. Scientists there have been studying this culture where heart disease barely exists. Here's NPR's Michaeleen Doucleff.
MICHAELEEN DOUCLEFF, BYLINE: Back in 1999, Michael Gurven was a young grad student in anthropology when he decided to take a daring trip deep in the rain forest. He hopped on a bus for 17 hours until the road ended.
MICHAEL GURVEN: Getting off the bus, you know, there was nothing - nowhere. So I just kind of started walking.
DOUCLEFF: And asking around about a group of farmers he had heard of called the Tsimane. They're an indigenous culture isolated from modern cities and still living like our ancestors did thousands of years ago.
GURVEN: And before long, I ended up at the house of the Tsimane government president.
DOUCLEFF: And instantly, Gurven was enchanted with the Tsimane lifestyle, hunting monkeys in the rain forest, fishing in rivers and drinking vats of beer made from fermented plantains. Gurven loved it so much, he decided to learn the language and live there.
GURVEN: It was really difficult. It was an intense time, and it was just amazing.
DOUCLEFF: And revealing. Over time, Gurven started to notice something about the Tsimane culture, that something was missing.
GURVEN: People just kind of clutching their chests and falling of heart attacks just isn't something that you ever really hear about.
DOUCLEFF: People didn't seem to have heart attacks, ever, which seemed kind of impossible, given that heart disease is common all around the world. So Gurven teamed up with a few cardiologists and started studying the Tsimane's hearts. Specifically, they measured the hardening of the arteries. What they found was striking.
GURVEN: Compared to the Americans, compared to a variety of countries in Europe, compared to Korea and even Japan, the Tsimane had the lowest level of atherosclerosis.
DOUCLEFF: In fact, the levels weren't just low. They were the lowest ever recorded in the world. Eighty-five percent of the Tsimane had no signs of heart disease at all.
GURVEN: And it wasn't only at age 50, 55, 60. But even up until, you know, past age 75, only 8 percent of Tsimane had atherosclerosis.
DOUCLEFF: So basically, even people that were in their 80s showed no signs of heart disease?
GURVEN: Yes, correct.
DOUCLEFF: Gurven and his collaborators recently published the findings in The Lancet journal. One of the cardiologists who helped with the study is Gregory Thomas at Long Beach Memorial in California. He says they're not 100 percent sure why that Tsimane have such spectacular hearts. But he thinks two major factors are at play. First off, the Tsmiane walk a lot. And I mean a lot.
GREGORY THOMAS: They exercise a huge amount, 17,000 steps for the men and 16,000 for the women.
DOUCLEFF: Sixteen thousand steps every day. That's like walking about seven miles every day. But here's the thing about this walking. It's easy, just like what you do naturally while fishing, farming or looking after the kids.
THOMAS: It's really the low intensity exercise for a long period of time. And we can do that really at any age. We don't have to be a 30-year-old at the gym looking strong. We can be going slow, but go long.
DOUCLEFF: And then there's the Tsimane diet. Thomas says it's very low in fat, especially saturated fat.
THOMAS: About 17 percent of their diet is wild game and 10 percent fish.
DOUCLEFF: But the rest, about 70 percent, is from carbohydrates. Now, we're not talking about bagels and baguette but unprocessed carbohydrates packed with fiber, like corn, plantains and tubers. Thomas says Americans can learn a lot from the Tsimane.
THOMAS: We don't necessarily want to go back to every family hunting and fishing for their self. It would be pretty dangerous to be doing that in most cities. But if we can practice some of that, we can benefit a lot.
DOUCLEFF: For starters, don't just go for 10,000 steps a day. Go for 15,000. And when selecting meat to eat, keep it lean. Maybe try some wild game. Michaeleen Doucleff, NPR News. Transcript provided by NPR, Copyright NPR.