When CT scans of ancient corpses revealed that even 4,000-year-old Egyptian mummies had clogged arteries, scientists jumped to a logical conclusion: Humans are sitting ducks for heart disease.
But a group of Amazonian hunters have proved them wrong.
The Tsimane people of the Bolivian rainforest have almost no deposits of calcium and cholesterol in their arteries, researchers reported in the Lancet medical journal earlier this year. What's more, they have the lowest rates of heart disease of any population ever studied.
By the time they turn 80, these indigenous people have the "vascular age" of typical Americans in their mid-50s.
The rest of us can take cues from their preindustrial lifestyle, said Dr. Gregory Thomas, co-author of the study and medical director of the Long Beach Memorial Medical Center in California.
He attributes the Tsimanes' strong heart health to their strenuous daily activities, not genetics. "I think the most important thing is likely exercise."
Unlike ancient Egyptian nobility, the Tsimane do not eat rich foods and sit on their thrones all day. Instead, they spend most of their waking hours hunting, fishing, farming and gathering foods along Bolivia's Maniqui River. Tsimane men walk the equivalent of 17,000 steps a day. Women tally about 16,000 steps. "They're like triathletes for their whole lives."
The average American, however, only manages about 6,000 daily steps.
Smoking is rare among the Tsimane, who number about 16,000. So are fatty foods. As much as 72 per cent of their calories come from high-fibre plants: plantain, rice, manioc, corn, nuts and fruits. Wild game – monkey, deer, rodents, birds, pig – makes up 17 per cent. The remaining percentage comes from freshwater fish, mostly piranha and catfish.
Nevertheless, diet probably isn't the biggest factor in their remarkable heart health, Thomas said. When North Americans follow a low-fat diet, he pointed out, "they still tend to get atherosclerosis [hardening arteries]."
Thomas and colleagues are combing through genetic samples from the Tsimane to look for markers that might explain their resistance to heart disease. But so far, the evidence suggests that the Tsimane may be as physiologically vulnerable to heart disease as everyone else. Their cholesterol levels have crept up since 2011, coinciding with the arrival of outboard motors that have given them quicker access to market towns – and processed foods – with less paddling by raft or canoe.
Until more data comes to light, Thomas said, the protective effect of exercise is the biggest takeaway from the study. Even if North Americans never achieve the Tsimane's level of physical activity, getting more daily exercise may be enough to delay the onset of heart disease, "so instead of getting a heart attack at 60, we get it at 90."