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The Tsimane are an ancestral population who live in the rainforest of Bolivia. They source food from a combination of horticulture and foraging. They have a known high burden of infection and inflammation. Yet their risk of cardiovascular disease is among the lowest in the world.

Another nearby group, the Moseten, are genetically similar to the Tsimane. This group is more modernized than the Tsimane, but not to the degree of the United States.

A recent study, published in the American Journal of Clinical Nutrition, analyzed the diets of these two populations for five years and compared them to the modern U.S. diet. The study cohort included 1299 Tsimane aged 30 to 91 years and 229 Moseten aged 30 to 84 years, both men and women.

The authors found that the Tsimane diet was higher in energy than both the Moseten and U.S. diets (2422-2736kcal/day). It was also higher in carbohydrate (376-423g/day, or 64 percent of calories). Protein intake was also higher among Tsimane than in the other two populations at 119-139g/day. Fat intake was much lower among the Tsimane at 40-46g/day. The Tsimane dietary diversity was slightly lower than that of the Moseten and much lower than that of the U.S.

The Tsimane primarily consume complex, unrefined carbohydrates such as plantains, rice, and corn. Their protein sources are fish and wild game. They rarely use added fats, sugar, or salt. Their fiber intake (average 26-29g/day) is higher than the U.S. intake, but not above the daily recommendation.

The study authors concluded that, although high-calorie, high-carb diets are associated with cardiovascular disease in modern societies, this association does not hold true among the Tsimane. The authors suggest that the Tsimane have a variety of protective factors against CVD that counteract the effect of their high energy and carbohydrate intake. These protections include a physically active lifestyle, high fiber intake, and a lack of processed foods. They also have a lower average BMI than Americans.

Interestingly, the Tsiminae diet transitioned closer to that of the modern industrialized diet during the five-year period of this study. The authors observed an increase in body fat over this time, a known marker of CVD risk. Thus, as the Tsimane diet transitions away from the traditional model, they become less lean.

One important thing to note about this paper is that other studies have suggested that the lower blood lipids and CVD risk of the Tsimane are, in fact, related to their higher average inflammation due to their high burden of infection and disease. Another factor that lowers their CVD risk is their short life expectancy (53 years on average). There is no data to show what the CVD risk of the Tsimane would be if they lived to the ages where CVD is more common. Thus, diet is not the only factor affecting the Tsimane CVD risk.

Based on this study, it would be a mistake to conclude that a high-energy, high-carbohydrate diet is the best way to decrease CVD risk. There are ancestral populations with low CVD risk at a large range of macronutrient intakes.

Instead, this paper supports the idea that diet quality is more important than macronutrient ratios, and that minimally processed diets are critical for longevity. Physical activity and healthy body composition (fat vs. fat-free mass) are also important drivers of CVD risk. A Paleo diet at a macronutrient ratio that best suits the individual is the best approach for long-term health and decreased CVD risk.