64 percent of the Tsimané’s daily calories come from complex carbohydrates high in fiber, including manioc root, plantains, maize and rice that they grow on family farms. / Courtesy of Michael Gurven

Researchers have found that the Tsimané people of the Bolivian Amazon have the healthiest hearts in the world.

With minimal levels of hypertension and type 2 diabetes, as well as the lowest levels of coronary artery disease ever recorded, the Tsimané population is a source of great interest for many reasons.

“The first question everyone wants to know is why do they not have heart disease? Is it magic genes, is it food, is it activity, is it social life, is it something else? So we’re starting to analyze everything one at a time,” Michael Gurven, a UCSB professor of anthropology and senior author of the study, said.

Along with postdoctoral researcher and lead author of the paper Thomas Kraft, Gurven is part of the Tsimané Health and Life History Project that began in 2002 to study the health, aging and behavior of the indigenous group.

The researchers recently focused on understanding the diet of the heart-healthy Tsimané. Over a five-year period, they gathered data through multiple 24-hour dietary recalls for nearly 2,500 Tsimané people. They then compared the Tsimané diet to the typical American diet.

Their study, “Nutrition transition in 2 lowland Bolivian subsistence populations,” has been published in the American Journal of Clinical Nutrition.

“We were looking at the population-level diet, but we were able to bring it down to the individual level to the extent that if I can look at what you specifically are eating, I can tell whether your eating patterns differ based on whether or not you have schooling, whether or not you live really close to town and the markets or if you live remote, really far away,” Gurven said.

The Tsimané had a high daily caloric intake (2,422 for women and 2,736 for men), with their diet consisting of high levels of carbohydrates and proteins and low fat (64, 21 and 15 percent, respectively), compared to those of people in the U.S. Despite low dietary diversity, the Tsimané had an adequate macronutrient intake. While intake of dietary sodium, calcium and vitamins D, E and K was lower, intake of daily fiber and minerals linked to cardioprotective effects such as potassium, magnesium and selenium greatly exceeded that of Americans.

One of the take-home messages is that the high-carbohydrate Tsimané diet may rebut paleo and Atkins-type diets that minimize carbohydrate intake with the belief that they will lead to a healthy heart. In fact, the Japanese Okinawan diet features an even higher carbohydrate level (85 percent) and Okinawans are some of the longest living people in the world, Gurven said.

“That’s the thing about diet — some people study it formally, but everyone has strong ideas about it and about what one needs to eat or not eat in order to be healthy,” Gurven said. “At least one thing we can do [with this study] is dispel certain kinds of myths.”

Some straightforward aspects of the Tsimané diet include not eating processed food or drinking many sugary beverages, which make for low, refined sugar and refined carbohydrate intake. At the same time, the Tsimané consume meat (mostly fish) and numerous complex carbohydrates including plantains, corn, brown rice and sweet manioc in the form of beer.

“So those aspects of the diet and eating a lot of calories — the Tsimané eat more calories per day than we do even though they’re probably two-thirds the size of an average American — isn’t inconsistent or incompatible with having a healthy heart,” Gurven said.

However, diet doesn’t cover the larger story of the Tsimané’s lack of atherosclerosis (narrowing and hardening of the arteries).

The Tsimané population may consume more calories but are also much more physically active, walking three times more in a given day than the average American. Concurrently, their immune systems are more active as they continuously fight off multiple pathogens, leading to greater energy expenditure. The researchers estimate 10 percent of the Tsimané people’s resting metabolic rate is spent just for immune activation.

Although the Tsimané are relatively isolated, increasing access to market goods may change aspects of their diets. One key feature of the study was to observe if the Tsimané diet was changing over time, and if there were differences in diet among people living closer to town versus those living a more traditional lifestyle.
Within the past five to 10 years, there haven’t been overall changes in the Tsimané diet, but there have been certain changes in health due to increased access to certain additives including processed sugar, cooking oil and salt.

“Everything gets fried — even the rice is fried. Even when they’re boiling it in a stew, it’s fried first. These additives have increased quite dramatically, and more so closer to town,” Gurven said.

Over the research period, the scientists noted that percentage body fat, body mass index (BMI) and proportion of the overweight and obese have increased within the population. Total energy and carbohydrate intake of the Tsimané increased significantly. Their consumption of sugar, oil and salt also consistently increased over time.

In addition to eating a high-fiber, low-fat diet, the Tsimané lead extremely physically active lives. Activities such as hunting, foraging, farming and fishing keep men physically active an average of 6-7 hours daily and women active for 4-6 hours. / Courtesy of Michael Gurven

To enhance their study, the researchers collected similar data from the ethnolinguistically and genetically similar Mosetén population. Another Bolivian indigenous group, the Mosetén differ in that they were acculturated into the Bolivian national system earlier than the Tsimané. The Mosetén have greater access to electricity and running water and more connections to town. They still live a somewhat subsistence lifestyle, but with more access to market goods, they rely less on wild game and fish.

The Mosetén served as a kind of “counterpoint” to the Tsimané to show what the latter group might look like 15 years from now, Gurven said.

The researchers found that compared to the Tsimané, the Mosetén ate a lot more sugar, used more cooking oil and ate much more dried meat that they bought in the market. On average, they were heavier and more sedentary, with higher cholesterol levels and blood pressure.

“We suspect that the Mosetén are going to be somewhere intermediate, with more heart diseases than the Tsimané but still less than [Americans],” Gurven said. “And so the idea was that we could look at their diet and they’ll be further along in terms of access to processed foods [than the Tsimané].”

Still, the Mosetén diet “isn’t all bad”, Gurven explained. It is more diverse than the Tsimané diet, and diversity tends to allow for better micronutrient access. Only nine items, characterized mostly by starchy staples, meat and fish, accounted for 75 percent of the Tsimané diet. The Mosetén diet featured a greater number of individual food items, and more calories came from dairy, legumes and other fruits and vegetables.

As the Tsimané and Mosetén populations experience an ongoing nutrition transition, the study illustrates the link between diet and an increase in noncommunicable chronic diseases. With more salt, oil and processed sugar being included in their diet, the Tsimané face potential negative health consequences that suggest findings of minimal cardiovascular disease may not endure.

“Part of my interest is not just what lessons we can learn for America but how can we think about and help prevent any onslaught of chronic disease that might face this population in the same way that has faced native North Americans all over, Australian aborigines, etcetera. If diet doesn’t change all that much, but all of a sudden people’s activity drops substantially, then what happens? So there’s this change that’s occurring. We’re trying to use our understanding of how this works to see at what risk [for heart disease] these people might be in in the future,” Gurven said.

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