The headlines on Friday 17th March were effectively “Call off the search – we’ve found the healthiest hearts in the world.” They had been found in the Tsimane people of Bolivia. The headlines came from a study in The Lancet, the summary of which can be seen here. I’ve got a copy of the full PDF to save you the bother.
This was an impressive study – at one level anyway (the nutritional/diet part was another matter, as we’ll see). Researchers had examined the people of Tsimane – a Bolivian population living what was described as a “subsistence lifestyle of hunting, gathering, fishing, and farming…” The researchers managed to study 705 Tsimane people and compare them with 6,814 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) to contrast a subsistence population with men and women from six communities within the American population. The main measurement was Coronary Artery Calcium (CAC), as an indication of coronary atherosclerosis. CAC scores higher than 100 were considered representative of significant atherosclerotic disease.
I say “managed to study” because that was one of the aspects that most impressed me – the Tsimane Health and Life History Project team (THLHP) has been working with this population since 2002. The researchers explained that the high participation rate was due to: i) long term trust established; ii) free access to medical specialists who helped with other ailments; iii) free food, travel and lodging while attending the assessments; and iv) compensation for the participants in the form of tools, needles and yarn – high value items when living off the land.
The results of the CAC scans were that 596 (85%) of the 705 Tsimane had no CAC; 89 (13%) had CAC scores below 100 and 20 (3%) had CAC scores higher than 100. This was a five-fold lower prevalence than the industrialised populations studied. The researchers reported other findings: mean LDL and HDL cholesterol levels were 2·35 mmol/L (91 mg/dL) and 1·0 mmol/L (39·5 mg/dL) respectively. Additionally obesity, hypertension, high blood sugar, and regular cigarette smoking were rare.
The “interpretation” part of the abstract reported that “the Tsimane, a forager-horticulturalist population of the Bolivian Amazon with few coronary artery disease risk factors, have the lowest reported levels of coronary artery disease of any population recorded to date.” That bit was fine. The next bit wasn’t: “These findings suggest that coronary atherosclerosis can be avoided in most people by achieving a lifetime with very low LDL, low blood pressure, low glucose, normal body-mass index, no smoking, and plenty of physical activity. The relative contributions of each are still to be determined.”
In this final sentence, indicators have been mixed up with lifestyle factors. Blood lipids, blood pressure, blood glucose and body mass index are indicators of health. They are outcomes. Not smoking and doing plenty of physical activity are lifestyle factors. They are inputs. To be of any transferable value, industrialised populations need to know what inputs make a difference. The most fundamental difference between the Tsimane and New Yorkers is that the former live as we evolved to live. The latter live anything but the life we evolved to live. This brings us to the first of five observations about this study:
1) Heart disease is a disease of civilisation.
What this study fundamentally showed is that heart disease is a disease of civilisation. That was the single biggest finding, but it was not reported as such. The UK Times newspaper quoted Tim Chico, reader in cardiovascular medicine at Sheffield University: “Would I live like the Tsimane to reduce my risk of heart disease? No way. But what I would learn from them is that my risk of heart disease is largely determined by what I do not what I am.”
Sorry Chico, but if you want the arteries of the Tsimane, you need to live like the Tsimane. What industrialised people do is so dramatically different to what the Tsimane do that even emulating some of their transferable habits (not smoking for example – good luck with the 6-7 hours physical activity a day) won’t negate the impact of modern life. Pretty much the only worry for the Tsimane person is where the next meal is coming from. The industrialised person lives in a world of chemical, noise and light pollution, the combination of stimulants and constant fatigue and they worry about everything from terrorism to should I have a muffin with my skinny latte?!
The reporting of The Lancet paper variously implied that having low cholesterol and/or a high carb diet would give one the arteries of an Amazonian hunter. Puh-lease! This does bring us on to the second point…
2) The diet was assigned great significance, but this was not a dietary study. (It did support the real food message however).
The study lead author, Professor Kaplan was quoted as saying: “Their [the Tsimane] lifestyle suggests that a diet low in saturated fats and high in non-processed fibre-rich carbohydrates, along with wild game and fish, not smoking and being active throughout the day could help prevent hardening in the arteries of the heart. The loss of subsistence diets and lifestyles could be classed as a new risk factor for vascular ageing and we believe that components of this way of life could benefit contemporary sedentary populations”.
The only detail about diet in The Lancet paper is on p7 – part of one paragraph contains the following: “An estimated 14% of their [the Tsimane] average caloric diet is protein, 14% is fat, and 72% is carbohydrate. (Ref 30) Meat protein and fat are acquired by hunting with guns and bow and arrow, or fresh water fishing with arrows, hook and line, or nets. Non-processed carbohydrates are grown in the form of rice, plantain, manioc, and corn via slash-and-burn horticulture, and the Tsimane also gather wild nuts and fruits. Importantly, carbohydrates are high in fibre and very low in saturated fat and simple sugars, which might further explain our study findings. The Tsimane diet lacks trans fats, and is a low fat diet, with an average estimated daily consumption of 38 g fat, with 11 g saturated fat, 14 g monounsaturated fat, and 8 g polyunsaturated fat. (Ref 30)”
This tells us that the researchers did not study the diet of the Tsimane (despite having worked with this population since 2002!), but relied upon another paper for details about the diet. This other paper, reference 30, can be seen here. The full paper is available. As you can see from the title, it is primarily about breast milk.
On p7 of this breast milk paper, we find the passage from which The Lancet researchers took details without question: “In 24-hr dietary-recall interviews taken at milk collection, 83% of the Tsimane mothers reported eating fish at least once the day prior; 63% reported eating meat, 49% reported eating both and only one reported eating neither. From previously gathered population-wide dietary observations, we estimate that for adults aged 20 and older, the average Tsimane diet comprises 74% plant and 26% animal foods. Locally cultivated staples (rice, plantain, manioc and corn) account for 66% of total dietary energy, wild and cultivated fruits and nuts 6%, and market foods (crackers, bread, pasta, sugar) 2%. Game meat (primarily species of peccary, tapir, capybara and monkey) accounts for 17% of total dietary energy; freshwater fish 7%; and beef, poultry, and pork from free-ranging animals 2%. The Tsimane do not consume domestic milk or dairy products, and eggs account for less than 0.5% of the diet. An estimated 14% of average daily energy is derived from fat, 14% from protein and 72% from carbohydrates. Minimally, the average adult Tsimane diet contains 38 g fat per day, with 11 g saturated fat, 14 g monounsaturated fat and 8 g polyunsaturated fat. “
This immediately tells us “Houston, we have a problem.” Notwithstanding the inaccuracy of dietary-recall, let’s take these numbers at face value. If 26% of energy comes from animal foods and dairy products are not consumed, then 26% of energy comes from fat and protein for starters. There is essentially no carbohydrate in meat, fish and eggs. The remaining non-animal 74% has been assumed to be virtually all carbohydrate, which is wrong (74% plant foods has become 72% carbohydrate with no further explanation). The only substance that is 100% carbohydrate is sucrose and that forms part of less than 2% of the overall Tsimane diet. The plant percentage includes nuts – Brazil nuts are available in Bolivia and they are 66% fat, 14% protein and just 12% carbohydrate (water, ash & minerals make up the rest). Wild rice is 15% protein and white corn is 9% protein and 5% fat. The assumption that non-animal foods are entirely carbohydrate is nutritionally ignorant and was not questioned by The Lancet authors.
The good thing about the Tsimane diet is that it is 98% real food. The first principle of dietary advice among the growing group of people who reject the dietary guidelines is: EAT REAL FOOD! The market foods aside, this is a real food diet and the absence of junk is where much of the benefit will lie (as seen in Seventh Day Adventist studies). Our second dietary principle is to choose that real food for the nutrients it provides and this drives people towards meat, fish, eggs, dairy, green leafy vegetables, nuts and seeds – foods that just happen to be naturally high in fat and/or low in carbohydrate. The Tsimane will likely not be eating so much carbohydrate by choice, but as a necessity when animals and fish are more difficult to catch. Interestingly, The Lancet article reports that some health indicators have worsened among the Tsimane “coincident with the availability of small gasoline motors”, which have enabled easier access to the market town and thus easier access to refined carbohydrates/fake food.
3) The level of physical activity is significant.
The diet is not 72% carbohydrate; we don’t know what the macronutrient composition of the Tsimane diet is. However, it is safe to assume that it is high in carbohydrate – the addition of horticulture to hunting and gathering will have given the Tsimane access to far more food – mostly carbohydrate/protein crops.
The Lancet paper tells us that “Men and women spend a mean of 6-7 and 4-6 hours per day engaging in physical activity respectively. Less than 10% of Tsimane daylight hours are spent engaged in sedentary activity, while more than 54% of waking hours are sedentary in industrial populations.” The Amazon foragers thus have most of their waking day to burn off the carbohydrate intake they consume (remember carbohydrate can only be used for fuel, it cannot be used for the body maintenance and repair roles undertaken by fat and protein). Adopting the Tsimane carbohydrate intake, without their hours of activity, would be a recipe for diabetes and obesity.
4) The low fat high carbohydrate diet has not produced girth or height.
Table 1 in The Lancet paper tells us the physical characteristics of the Tsimane people studied. Approximately equal proportions of men and women were studied. Sadly the weight and height data were not split by gender, but the combined details are still striking. The average height of the Tsimane men and women is 155cm – 5 foot; their average weight is 58kg – 128lb. The inhabitants of NY, LA, Baltimore, Chicago, among other communities, involved in the American comparator group, may consider those dimensions too high a price to pay for low Coronary Artery Calcium scores.
5) Cholesterol levels support my latitude finding.
In 2009, when studying the Seven Countries Study, I noticed that, for the 7 countries and 16 cohorts, the correlation between coronary heart disease and cholesterol was substantially less impressive than the correlation between coronary heart disease (CHD) and another factor. That factor was latitude. The correlation was almost perfect: 0.96 for the 7 countries and 0.93 for the 16 cohorts.
This also made sense. The closer the country/cohort to the equator, the more sunshine and therefore the more cholesterol that had been turned into vitamin D. The lower heart disease could be a result of higher vitamin D, with cholesterol nothing more than the marker of cholesterol and concomitant vitamin D levels.
In the Seven Countries Study the highest latitude number (64 degrees north) was for north Karelia (Finland), which had the highest death rate from CHD. The lowest latitude numbers were in Japan (32-33 degrees north), which had the lowest death rate from CHD. The latitude for Bolivia is 16 degrees south – even closer to the equator and the Tsimane will reside outdoors far more than industrialised populations. If industrialised populations want to emulate the heart health of an Amazon tribe, they should forget statins and move to the rain forests.
The takeaway message
Heart disease is a disease of civilisation and that’s pretty much it. Industrialised people can do some helpful things to minimise heart disease (don’t smoke, be active and live outdoors near the equator). However, there is a world of difference between the lifestyle of remote tribal people and Wall Street bankers. If you think eating several hundred calories of even unrefined carbohydrates, without being active for approximately 6 hours a day, will help, even without addressing the numerous and significant other stresses and exposures of modern life, you’re in for a disappointment at best and diabetes at worst.