An ancestral model of hypertension prevention: The Tsimane
For several years I have appreciated the idea that when people live life in a way that is strongly divergent from the niche(s) in which we evolved, biological problems will arise. For example the diseases that plague America today such as diabetes, obesity and hypertension, to name a few, are largely thought to be lifestyle-related. David Lieberman discusses the idea of “mismatch diseases” in his recent book, The Story of the Human Body.
I can attest personally to a poor lifestyle leading to a mismatch disease as I used to have hypertension during my teens and early twenties. In my early college years I adopted a culmination of lifestyle factors that ultimately led to an intertwined habit-building network of further weight loss, better stress management, a better sleeping routine, a high vegetable diet and supplementing my resistance training with more cardiovascular conditioning exercise*. I got to the point where I no longer needed medications. Most of the lifestyle factors I mentioned are recommended by various organizations with a vested interest in hypertension and independent researchers who have conducted reviews of the literature (1,2,3). Interestingly following most of these recommendations would put one closer in accordance to a lifestyle led by our ancestors (4).
While a number of studies have investigated populations living an ancestral lifestyle to measure parameters such as lipids, blood glucose, and hormones such as leptin I had not seen a study on the influence of an ancestral lifestyle on blood pressure regulation until recently (4). I find this to be exciting news as hypertension is the most prevalent cardiovascular disease (CVD) related risk factor seen by physicians in the US and CVD is the leading killer of Americans (1,5,6). The prevalence of hypertension in the USA is staggering with a lifetime risk in the U.S. at 90%! (5) At any given time roughly a third of our population is estimated to be hypertensive (1,5).Direct and indirect costs associated with hypertension such as prescription costs, trips to the physician, and lost days of work were estimated to total $131,000,000,000 annually in 2012 (7).
The study was conducted by a team of researchers led by anthropologist Michael Gurven on the island Tsimane, Bolivia (4). The Tsimane are somewhat divided in that some still live a hunter gatherer lifestyle while others have adopted agriculture and more permanent settlements. Nonetheless they are living more similar to ancestors than contemporary cultures. Their food is obtained via fishing, hunting, and cultivation of bananas and manioc. Physical activities are necessarily high and there is low prevalence of overweight and obesity. In this study over 2000 individuals were followed with a mean follow up time of roughly eight years. Over 6500 measures of blood pressure were taken by the research team. The primary findings were that only 3.9% of women and 5.2% men were found to have hypertension at any point during follow up. Only about 3% of the population had persistent or reoccurring hypertension. In the statistical model used by the researchers it was found that smoking was not a predictor of elevated blood pressure nor was Spanish fluency which was used as a surrogate for contact with modern society. In contrast “lean physique”, physical activity, and a “protective diet” were found to be inversely related to incidence of hypertension.
While it might be simple to conclude that exercise, fruits and veggies, and not becoming fat are the keys to avoiding hypertension, I believe there are a few other factors that deserve some consideration including life satisfaction and happiness, in addition to sunlight exposure. In regards to life satisfaction, as noted earlier, stress reduction is a life behavior recommended to combat hypertension (2). In a culture where one might assume a greater sense of community and camaraderie, and lack contemporary life stressors such as fighting traffic, constant deadlines coupled with social isolation, it’s tempting to assume that lower levels of stress may contribute to reduced blood pressure. In his book Outliers Malcom Gladwell discussed some interesting observations made in Rosettan Italians who at one point were known for having wonderful health when they lived in close-knit communities despite their mediocre diet, yet went on to experience health decrements upon leaving their neighborhoods (8, 9).
In regards to the note on sunlight exposure, studies have shown that UVA light (sunlight is UVA and UVB) exposure contributes to the reduction of massive stores of nitrate/nitrite in the skin to nitric oxide - the primary blood vessel dilator in the body (10). Watch this interesting TED talk for further discussion on the role of sunlight in nitric oxide production (here).
In summary I believe the idea that the epidemic of hypertension being a mismatch disease is remarkable and pretty compelling. While we all can’t go back to living like our ancestors we can take action steps towards being healthier people, such as avoiding binge drinking, moving more and engaging in exercise and eating more fruits and vegetables (particularly vegetables). Below I’ve summarized some common lifestyle recommendations to prevent and treat hypertension. Many of these lifestyle modifications are about as efficacious as most first line anti-hypertension medications and when combined could go a long way to prevent or attenuate hypertension (1, 11).
*I didn’t really do much traditional cardiovascular exercise (except for 5 to 10 minute warm ups and cool downs surrounding resistance training) but I did a lot of sprints, jumping rope, circuit training, etc. I also starting eat more vegetables. Despite being unaware of dietary nitrate and its role in potentially lowering blood pressure and improving vascular health I knew that vegetables were full of vitamins, minerals, plant chemicals and just generally very healthful.