People Living in Amazon Rainforest Provide Clues to Coronary Protection

WASHINGTON, DC—A remote Bolivian group, living far from civilization and subsisting primarily on their hunting and gathering skills, has the lowest levels of atherosclerosis ever recorded.

According to a study presented here today at the American College of Cardiology (ACC) 2017 Scientific Session and simultaneously published in the Lancet, the indigenous people, known as the Tsimane, may have much to teach modern society about living a healthy lifestyle and limiting cardiovascular risk factors.

Investigators led by Hillard Kaplan, PhD (University of New Mexico, Albuquerque), found that 85% of the Tsimane people studied had coronary artery calcium (CAC) scores of 0 as measured by non-contrast coronary CT scan. Among the subgroup of people over age 75 years, approximately 65% had CAC scores of 0, and just four individuals in their 80s had moderately elevated CAC (> 100). The incidence of CAC > 100 in the entire Tsimane population was 3%, which is about one tenth the prevalence in a matched industrialized population. In addition, incidences of obesity, hypertension, high glucose concentrations, and cigarette smoking were rare overall.

The study authors say their findings suggest that the typical 80-year-old Tsimane individual has coronary arteries similar to those of a 52-year-old from an industrialized nation.

In his presentation, Kaplan said the implication of the findings is that “even preclinical coronary artery disease can be avoided in the vast majority of people in the setting of very low CAD risk factors and hours of daily physical activity.”

Activity, Diet Keys to Fewer Risk Factors

The study, which is part of the larger Tsimane Health and Life History Project being conducted by the University of New Mexico, included 705 individuals from 85 Tsimane villages in central western Bolivia in the Amazon rainforest. Those who underwent CAC scoring ranged in age from 40 to 91 years. The Tsimane people live a subsistence lifestyle that includes hunting, gathering, fishing, and farming, with an average of 6-7 hours per day of physical labor for men and 4-6 hours for women. In addition to fish and game, the Tsimane consume a diet high in nonprocessed fiber-rich carbohydrates such as rice, plantain, manioc, corn, wild nuts, and fruit. Compared with an average US diet of about 50% carbohydrates, the Tsimane consume about 72%. They eat very little saturated fat, however, and no trans fats. Total daily averages of fat intake per person, according to Kaplan, are around 38 g, or about 9% of total daily dietary intake. In comparison, the typical US diet consist of about 23% fat, he noted.

While the lesser amount of coronary calcium contributes to the slower progression of atherosclerosis, Kaplan and colleagues say, the reasons behind the very low CAC scores is unknown. Previous studies have shown that the group generally has low LDL cholesterol (92.8 mg/dL on average), although increases have been seen in recent years that could eventually translate to increased CAC scores. These increases may have been caused by recent acculturation, primarily due to venturing into towns to acquire motors for their handmade wooden canoes, he said.

Importantly, the Tsimane also tend to have low HDL cholesterol (38.7 mg/dL, on average). Although typically considered a risk factor, the low HDL may be offset in the Tsimane by low total cholesterol and lifestyle factors. Prior studies also have shown that over a 5-year period, only one in 50 deaths that occurred within the group was due to MI.

Because they live in the rainforest, the Tsimane are at high risk for infectious diseases, parasites, and inflammation. “Although they don’t die of heart disease, they do die of infections, accidents, and so forth,” he added.

Exercise is another key component of what keeps the Tsimane’s coronary arteries in such great shape. Tsimane men average about 17,500 steps per day across their adult life, while women average a little over 15,000. In comparison, the average American gets about 6,000 steps per day, Kaplan observed.

Following the presentation, panelist Kim A. Williams Sr, MD (Rush University Medical Center, Chicago, IL), said the study “gives new meaning to the phrase ‘will work for food,’ because most of us don’t in the way that [the Tsimane] are.” He also commented on lack of dairy in the diet, and noted that the study is more support for the idea that a plant-based diet “seems to be very protective.”

Photo Credit: Ben Trumble