Researchers map out the diet that may have rendered a Bolivian people 'immune' to heart disease.
According to the Centers for Disease Control and Prevention (CDC), approximately 610,000 people die because of heart disease-related problems each year in the United States.
At global level, cardiovascular diseases caused around 31 percent of all deaths in 2016 alone, the World Health Organization (WHO) note.
The main modifiable factor that specialists focus on when it comes to prevention strategies against heart disease is diet.
American Heart Association (AHA) guidelines indicate that to keep heart disease at bay, a person should follow a diet that is rich in fruit, vegetables, whole grains, and oily fish.
Is this the best diet for the heart? A team of anthropologists from the University of California–Santa Barbara has recently decided to look for clues among the peoples of the Bolivian Amazon.
One particular population, called the Tsimane, are remarkable in that they almost never develop heart disease, and only very rarely do they have hypertension, unhealthful cholesterol levels, obesity, or type 2 diabetes.
The researchers thought that one key factor in the Tsimane's seeming imperviousness to heart disease might be their diets. The Tsimane, the investigators note, have so far been minimally influenced by globalization trends.
Their food tends to come from natural sources, and they purchase very little produce from markets. In this respect, the Tsimane differ from their neighbors, the Moseten, with whom they share the same language but not the same diets and lifestyles.
A carb-rich diet
Unlike the Tsimane, who are more sheltered, the Moseten acknowledge outside influences, which have impacted their dietary habits as well as their lifestyles. As a result, the Moseten may also be more at risk of cardiovascular and metabolic diseases when compared with their more isolated "cousins."
"Our prior work," says senior study co-author Prof. Michael Gurven, "showed that the Tsimane have the healthiest hearts ever studied, so naturally there's a lot of interest in understanding why and how."
So, to understand what sets the Tsimane apart and allows them to enjoy such perfect heart health well into old age, the researchers interviewed them about their daily dietary and lifestyle choices.
"We conducted a detailed analysis of the Tsimane diet and then compared it to what modern Americans typically eat, and to the diets that claim to be heart healthy," says Prof. Gurven.
The investigators also compared the Tsimane's choices with those of the Moseten, the people with whom they are most closely related. In total, the team spoke to 1,299 Tsimane and 229 Moseten, and they compiled detailed profiles of the two people's diets.
In the study paper that appears in the American Journal of Clinical Nutrition, the researchers report that the Tsimane's usual diet was high in carbohydrates and protein but low in fat.
The Tsimane diet was high-calorie — amounting to 2,433–2,738 kilocalories per day — and it comprised 64 percent carbs, 21 percent protein, and 15 percent fats.
Perhaps surprisingly, the Tsimane do not appear to eat a variety of foods. Instead, their meals tend to gravitate around a few dietary staples. The researchers say that about two-thirds of calories come from complex carbohydrates, present in foods such as rice and plantain.
Around 16 percent of calories come from fish — of which they eat over 40 different species — and another 6 percent from wild game. The Tsimane buy only 8 percent of their foods from the market.
The challenge of changing lifestyles
Another surprise, given the lack of great dietary diversity, is that the Tsimane do not have many micronutrient deficiencies. While this people tends to run low on calcium and some vitamins — such as D, E, and K — they absorb a lot of potassium, magnesium, and selenium.
These nutrients, the researchers say, may help boost cardiovascular health, and the Tsimane consume them at levels that are higher by far than the typical amount present in North American diets.
Furthermore, the Tsimane eat almost twice as many fiber-rich foods as the Moseten or U.S. populations. However, the researchers also express the concern that, as globalization trends increase, the Tsimane are slowly giving in to harmful influences from outside of their own society.
So, they found that over the 5-year period during which they conducted the present study, the Tsimane's total energy and carbohydrate intake soared, and many of them have started to add larger quantities of lard, oil, sugar, and salt to their diets.
"This is a key time," says the study paper's lead author, Thomas Kraft. "Roads are improving in the area, as is river transport with the spread of motorized boats, so people are becoming a lot less isolated compared to the past. And it's happening at a pretty rapid pace."
Prof. Gurven goes on to say that, given the opportunity to bulk-buy ingredients such as sugar, it is unsurprising that the Tsimane are, little by little, transitioning to less healthful diets. "Getting calories cheaply with less effort — who wouldn't?" he asks.
Yet, he also adds that the Tsimane's search for higher calorie counts may be due to the fact that they actually lead very active lifestyles.
"[They're] also physically active — not from routine exercise, but from using their bodies to acquire food from their fields and the forest, which is also an important lesson," says Prof. Gurven.
"You can't look at what you're eating irrespective of what you're doing with your body. If you're physically active, you can probably get away with more flexibility in the diet."
Prof. Michael Gurven