Academic ResearchHeart DiseaseNewsletter

South American tribe & heart disease

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.

The study

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.

19 thoughts on “South American tribe & heart disease

  • “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”. I don’t understand how you came to this conclusion, nor its relevance to your article.

    • Hi Philip
      Because hunter gatherers value produce from hunts higher than produce from gathers. You can simply get more energy and more valuable nutrition from animals than from plants.
      The relevance is that the lead author 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”, as if somehow a tribe would be choosing fibre over fat.
      Best wishes – Zoe

  • Did they measure fasting glucose and fasting insulin and calculate any HOMA2-IR scores? My guess is the Bolivians mostly would score <5.5 mmol/L and 21-50 pmol/L (or at least less than their age), respectively. That is to say, the lack of hypertension, atherosclerosis, obesity and hyperinsulinemic diabetes mellitus would be due to an absence of insulin resistance.

    • Hi there – they measured fasting blood glucose only. This was reported in Table 1 as the proportion above a risk factor cut off, which was defined as >6.9 mmol/L. All age groups were either 0.00 or 0.01 (as a proportion) on this scale i.e. no-one!

      Hypertension in the same table was reported as proportion above 140 DBP and the highest this got was 0.1 in the 40-44 years old age group.

      Your lack of insulin resistance diagnosis looks good!
      Best wishes – Zoe

  • Well done Zoe, you spotted some things I’d missed.
    I found an earlier Tsimane’ paper which stated that the corn and manioc specifically were consumed as chicha (fermented beer). This would reduce carb % a bit. And in the Martin et al breast milk paper they state
    “our behavioural observations of foods eaten did not account for organ meat consumption or the addition of cooking fat, which may substantially increase saturated fat intake.”
    This would also increase total fat intake above 14%.
    Failure to account for organ meat consumption may also mean that the Tsimane protein intake was higher than 14%. They didn’t include organ meat, I think, because it wasn’t in the USDA tables they used to get nutritional values (but it’s unlikely these were very accurate for tapir, capybara, money, or piranha).
    According to Martin et al,
    “Tsimane women generally cook with rendered animal fat, and rarely purchase or use vegetable oils.”
    The milk composition values – very high in long chain PUFAs found only in animals and low in linoleic acid compared with US values – clearly show the importance of animal foods.

    • Thank you for this! We’re a good team from across the other side of the world eh?!
      Best wishes – Zoe

  • Thank you. I just shake my head when I read about these studies that are more about media and less about good science. This particular study and your great critique reminded me of the British doctors that were stationed in the forts and trading posts around the world in the 1800’s. As presented in Good Calories, Bad Calories, these doctors saw the same results that the above study saw. But those ole time doctors came to the similar conclusions as you did. Good science does not always require all of the modern equipment and mathematical evaluation tools of modern science. Just good old fashion – unbiased observation.

  • Outstanding critique, as usual. Were the researchers “massaging” the facts to promote an agenda?

    • Thanks Johnny – who know what’s going on with ‘research’ at the moment! It’s way too geared around media headlines, that’s for sure. “Eat more carbs” is a headline that ‘fits’ and, sure enough, it go big coverage. “To have great CAC scores, you need to live like the Tsimane people and in Bolivia” – not quite the same ring!
      Best wishes – Zoe

  • Another brilliant bit of delving and dispelling Zoe. Thank you for this.

    • I think exercise can help in ways other than by calorie-deficit.

      I’ll use myself as an example. I’m probably an outlier, (who shouldn’t even be talking here!) But here goes.

      Over the last couple of years I’ve lost perhaps 3 kilograms, dropping my BMI from about 20.5 to about 19, and losing an inch from my waist. This is during a period when I’ve switched pretty thoroughly to LCHF, accompanied by High Intensity exercises. (Interval Training, Resistance Training, and Isometric Training). I do those exercises before breakfast, hence typically 14 to 16 hours after last eating. (Although I’ve had some tea, whole milk, no sugar, before).

      I think what is happening is that those exercises burn visceral and ectopic fat. I don’t count calories – I eat until I run out of appetite. My small amounts of non-fibrous carbohydrate, and moderate amounts of protein, both raise blood-glucose levels. (That is my interpretation of my variations in blood-glucose levels over a day). This presumably gets stored partly in fat cells. But my exercises (after a long fast) presumably help deplete those cells – I appear to be at least partly fat-adapted.

      I think I am running my body as “thin on the inside”. If so, I am helping to achieve my objective of metabolic health, which is vitally important since I am nearly 70. Perhaps the Tsimane also run their bodies “thin on the inside”?

      I wonder if we worry too much about subcutaneous fat and not enough about internal fat? And sometimes interpret BMI incorrectly as a result?

      • I agree with you. I have, however, gone from 4 days/week to 3 then 2 and now 1 day/week of exercise. I now use Body by Science, which advocates short, very intense weightlifting once per week. Even with doing some extra back exercises every two weeks and rotator cuff exercises every week, and taking a shower, I’m out of the gym before most people are warmed up.

        I think the recommendation (at least in the US) of exercising 60 minutes a day, 6 days a week is to overcome the effects of the high carb, low fat diet they recommend. If you don’t eat HCLF, and instead eat LCHF (and I also fast regularly), I don’t think you need to exercise daily.

        • Thanks, BobM.

          I’ve read Body by Science twice. Obviously I’ve paid particular attention to chapter 11 (for seniors). One day I’ll be a senior, but I’m not even 70 yet!

          I do a sequence of planned exercises every two days. (I do them at home, not at a gym). Apart from HIIT on an exercise bike every 4 days, my major exercises are multiples of 4 days apart, at least 8 to avoid over-training. I use a variety of resistance and isometric exercises to build strength and resilience. And I pay particular attention to careful rotator-cuff exercises, having damaged my left-arm rotator-cuff tendon last year being over-enthusiastic with my exercises! So I suspect we are not very different.

          I agree with you that very intense exercises combined with LCHF and fasting has a very different effect on the body from moderate exercise, HCLF, (and perhaps a calorie-reduction diet). I appear to be maintaining or improving my health parameters year by year, and building up my strength almost month by month. I hope to keep this up for a long time, before I get old.

          (I am worried that I may be eating too much protein. I am trying to avoid the muscle-loss that occurs as we get older, and I’m even trying to add muscle mass. But excessive protein can itself be life-limiting. I don’t know how much the recommended amounts should be modified, either up or down, for someone my age).

          When I compare what I eat and do with the UK national guidelines, there is virtually no resemblance. I hope I’m not the one who’s lost the plot! It is as though those setting the guidelines are unaware of the last 10 or more years of nutrition and exercise science. This is a pity, because the consequences are devastating in both humanitarian and economic terms. There are probably some schoolchildren who have worse health-check parameters than me. That shouldn’t happen!

        • 60 minutes a day! I wouldn’t have the time or the strength after a days work.

    • BobM, I read your link and the corresponding study that contends that the Hadza and Westerners burn the same number of calories. Well yes and no. You would agree that China has a bigger GDP than the UK but the UK has a better GDP per capita, thus they are better off. The same principle applies here. Although the Hadza and Westerners have an approximate TEE, the Hadza burn more calories per weight kg (see Table 1 of the study).

  • On first hearing this I thought the ‘conclusions’ of the study fell right into the ‘eat less move more’ trap yet again. Is there any mention of any other ailments these people my suffer? I wonder also whether there was any mention of average life span and age distribution. This may of course skew any so called ‘outcome’. Also was there any mention of calories/day? If not that was an opportunity missed to confirm the paradigm. Seems to me that this was a one day headline and will sink into oblivion like the ‘eat 10 a day’ nonsense a few weeks ago, which, if memory serves was served up be an Australian study a few years previous. I just keep wondering who pays for all this.

    • The Tsimane’ have high levels of inflammatory markers – this study refutes the idea that any old inflammation will cause heart disease. Parasites and infections are causes of disease and early mortality, and iron deficiency anaemia is common in children.
      Maybe they just have zero CAC because their diets are deficient in calcium; but low iron would definitely lower CHD risk.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.