How to maintain a healthy heart is a surprisingly contentious question. Diet and exercise are crucial, everyone agrees — but the ideal specifics and the relationships among them remain mysterious. Some experts recommend avoiding dietary fats; others endorse fat and low carbohydrates. The impact of high levels of inflammation on heart disease is disputed. And almost no one can agree about how much (or what type of) exercise is optimal. But a study published last month in The Lancet points the way to resolving some of these issues by focusing on the Tsimane, a group of subsistence farmers and hunters living in Bolivia along a tributary of the Amazon River.
Anthropologists have learned a lot about the lives of the Tsimane since they began studying them 15 years ago. The men typically spend seven hours or so of every day hunting, fishing or poling their canoes to towns to sell and procure food. The women devote almost as much time to gathering nuts and farming rice, corn and plantains. Men and women each cover roughly eight miles, or 17,000 steps, each day. Their diet is heavy on carbs: 72 percent of their daily calories derive from unprocessed starches, 14 percent from saturated and unsaturated fats and 14 percent from protein. Many Tsimane experience frequent infections and show chronically elevated levels of inflammation.
For the Lancet study, anthropologists teamed with cardiologists who drew blood from 705 Tsimane men and women between the ages of 40 and 94. The researchers also conducted cardiac scans, enabling them to score the presence of atherosclerosis, a disease characterized by plaque buildup inside a person’s cardiac arteries. A score of 0 meant essentially no detectable disease; 1 to 99, low levels; and 400 or greater would be high. Eighty-five percent of the volunteers scored 0; only 3 percent exceeded 99. Even among those older than 75, only 8 percent exceeded 99. A single person scored higher than 399. As a group, the Tsimane had scores less than one-fifth those of people in the United States or Europe. They exhibited less atherosclerosis than even Japanese women, previously thought to have the world’s healthiest arteries. In general, the Tsimane developed the first signs of atherosclerosis almost 25 years later than their counterparts in the industrialized West.
The implications of these findings are complex, says Hillard Kaplan, an anthropologist at the University of New Mexico in Albuquerque and the study’s co-author. They raise questions about the effect of fats and carbohydrates on the heart and also about the cardiac impacts of inflammation, which does not contribute noticeably to atherosclerosis among the Tsimane. But Kaplan says the study indicates how essential it is to be very active physically — the Tsimane were in almost constant motion every day. The future of the Tsimane may tell us more about lifestyles and hearts, too. Modernity is intruding into their lives. Some now use motorized canoes, putt-putting up the river instead of poling by hand. Kaplan plans to continue monitoring his Tsimane volunteers. In a few years, their hearts may look more like ours.