We've all heard the adage about how it takes a village to raise a child. Now it has taken a group of villages — in Bolivia — to raise medical science's knowledge about how to prevent heart disease.
The Tsimane (pronounced "chee-may-nay") people lived essentially untouched by modern society until the early 1950s. This group of 16,000 people live in about 100 villages in the Amazonia basin, primarily surviving by hunting, fishing and farming, and follow a primarily plant-based diet. They walk miles every day.
A study published in the Lancet in March 2017 demonstrated that the Tsimane seem to be protected from developing coronary artery disease, even though their cholesterol levels were not especially low. This was discovered by doing a fascinating experiment. A well-established marker of premature heart disease is detection of calcium in coronary arteries. A research group brought a CAT scanner deep into the jungle to see whether this was found in the same manner as people living in a Western society. The arteries of an 80-year-old Tsimane had little evidence of disease, and looked more like those of a typical 50-year-old living in Philadelphia than of an octogenarian.
Living in Bolivia with the Tsimane is no bargain. There is much more hardship than missing out on television and cellphones. One of the most common incidental findings that the CAT scans showed was a 10 percent incidence of tuberculosis. Inflammation, often thought to be a major cause of worsening coronary disease in the west, was high because two thirds of the population was infected with an intestinal parasite.
But, the results are intriguing. The average LDL (bad) cholesterol was 95 mg/dl, which is considered high enough in this country to treat with statins, and the average HDL (good) was 39.5 mg/dl, which we would consider low. Despite this, and the elevated markers of inflammatory risk such as c-reactive protein, almost none of the older Bolivians who were studied had evidence of coronary artery disease.
A typical day in the life of a Tsimane involves farming, food preparation, a plant-based diet, and lots of walking, often six hours a day. This seems to matter more than their cholesterol levels.
The results of this study seem to contradict basic assumptions of the mechanisms that cause coronary artery disease. Much of our efforts to combat heart disease involve prescribing cholesterol-lowering drugs, and inflammation is thought to be another major contributing factor. Lowering cholesterol levels would not help the Tsimane, and their intestinal parasites cause lots of inflammation. This study suggests that there is still a lot that we do not know about how heart disease develops.
It is sad that there are indicators that things are changing for the worse for the Tsimane. Nearly a third of adolescents reported consuming sugary drinks, and listed processed foods such as sweets and pasta as part of their new diet, very different from their older parents and grandparents. Dental decay and obesity are new problems they are beginning to deal with as civilization makes further inroads. Heart disease is likely to follow.
Perhaps we could learn some lessons from this village to help prevent heart disease. There is no doubt that walking more, driving less, watching less TV, and eating less processed food and sugar will lead to less heart disease. We can all do without the parasites.