The Tsimane living in the Amazon have the lowest reported levels of age-related hardening of the arteries in the world, say researchers who encourage Westerners to learn from these Bolivian rainforest inhabitants.
Atherosclerosis was thought to be a natural part of aging. Even Egyptian mummies have shown signs of plaque buildup in the arteries.
For the study in Friday's medical journal The Lancet, cardiologists focused their low-radiation CT scanners on the Tsimane, a forager-horticulturalist population that eats mainly wild, lean game, plantain, rice and maize, and fruits and nuts.
The findings were presented Friday at the American College of Cardiology's scientific meeting in Washington.
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For a U.S. middle-aged man, the chance of having calcium in heart arteries is about equal to his age, and women in the U.S. trail that by 10 years, said study author Dr. Gregory S. Thomas, medical director of the Long Beach Memorial Medical Center in California.
Thomas didn't believe anthropologists who have worked closely with the Tsimane for nearly 20 years when they told him they suspected Indigenous Brazilians had no age-related atherosclerosis, so researchers designed a study to test it out.
Anthropology Prof. Hillard Kaplan of the University of New Mexico and his team asked 705 adults averaging age 58 to travel for days by boat and SUV out of the rainforest, and get scanned for coronary blockages. They also had their weight, age, blood pressure, cholesterol, blood glucose and inflammation markers checked.
Kaplan said undertaking the study involved fostering a special relationship with the Tsimane over decades.
"They trust us that we really do care about their best interests. Our arrangement with the tribal council is that we provide medical assistance regardless of whether you're involved in our study."
Nearly nine in 10 Tsimane had no risk of heart disease (596 of 705 people, or 85 per cent), 13 per cent had low risk and three per cent had moderate or high risk, according to the Lancet study.
Among those 75 or older, nearly two-thirds (31 of 48, or 65 per cent) had almost no risk and eight per cent had moderate or high risk — the lowest recorded levels of coronary artery disease of any population, the researchers said.
"We're just thrilled with the results," Thomas said, given its implications for slowing the progression of atherosclerosis.
Thomas said he was so impressed with the findings that he said even he would start doubling the amount of exercise he does.
Source of pride
The average man in the study does 17,000 steps a day and a woman does 16,000, mostly from walking to farm, hunt, fetch water and parent large families, Thomas said.
It's remarkable that the Tsimane's rate of progression of aging-related atherosclerosis can be so slow in their 80s, Thomas and Kaplan said.
The researchers found the average 80-year-old Tismane has the arteries of an American in his 50s.
"They're changing slowly, but what we're seeing is the beginnings of changes in their physiology," Kaplan said.
About 17 per cent of their diet is wild game, such as peccary (a species of wild pig), monkey, rodents, deer and pheasant-like birds, so they eat very lean meat and their diet is low in saturated fat. Another seven per cent of their food intake is freshwater fish, including piranha and large catfish. They get the bulk of their other calories from plants, many of them very high in fibre.
While cause of death of Egyptian mummies isn't clear, heart attacks are rare among Tsimane, said study co-author Michael Gurven, a professor of anthropology at the University of California Santa Barbara.
"Lifestyle does matter," Gurven said. "Take the big picture — what are the little things we can do that might make a difference? Some of them aren't new, like not smoking. That's a big one. But even in terms of what we eat, if we eliminated soda and eliminated sugar, that could go a long way potentially."
While highly processed foods now make up more than half of the average Canadian family's food purchases, experts advise urgent changes to fight rising rates of obesity, including cooking wholesome ingredients from scratch with a close eye on portion sizes.
Gurven's suggestions to squeeze in more physical activity include:
- Take the stairs.
- Improvise a standing desk.
- Cut back on sedentary time.
Cardiologists not involved in the research agree up to 80 per cent of premature heart disease and stroke is preventable through lifestyle behaviours.
The Tsimane enjoy a vibrant culture with improving rates of death and infectious diseases, but often face discrimination for their lifestyle from others in the Bolivian society, the anthropologists said.
"When we present some of these types of findings, the Tsimane take pride in it," Gurven said.
Canada lacks prevalence data nationally or provincially on atherosclerosis, according to Heart & Stroke, a non-profit charity. Statistics Canada reports more than 1,600 deaths per year from atherosclerosis.
In response to the mummy findings, the British Heart Foundation noted calcified arteries could also be caused by other ailments.