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Expert reaction to study looking at health of arteries of the Tsimane group in South American

A new cross-sectional cohort study published in The Lancet reports 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.

 

Dr Tim Chico, Reader in Cardiovascular Medicine / consultant cardiologist, University of Sheffield, said:

“The present study found that the Tsimane had much lower levels of coronary artery calcification than previously found in other populations, in fact the lowest of any population so far measured.  This is an interesting finding but this study cannot explain why the Tsimane have such low levels of coronary artery calcification.

“The authors speculate that the low coronary calcification in the Tsimane is due to their lifestyle.  Since we know that regular exercise, being a healthy weight, not smoking, and a healthy diet all reduce the risk of heart disease, these results are not too surprising since the Tsimane fulfil almost all of these.  It is important not to romanticise the Tsimane existence; two thirds of them suffer intestinal worms and they have a very hard life, without fresh water, sewerage or electricity.  The rates of diseases other than heart disease are much higher in the Tsimane than in the West, particularly infections (1% of the Tsimane had possible tuberculosis, a much higher rate than in the West).

“This study performed a test called coronary artery calcium scoring using a CT scan, which gives an indication of how likely someone is to get coronary artery disease.  One limitation is that they only did this in the Tsimane people and did not have a control group that they assessed at the same time, but they did compare the findings with other similar studies in different populations, including in Japan and North America.  Overall I think the findings of this study are reasonably robust.

“So, 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, and that I can greatly reduce my risk of developing a heart attack if I am regularly active, if I eat a diet rich in vegetables and low in processed foods, maintain a healthy weight, and don’t smoke.”

 

Prof Sir Nilesh Samani, Medical Director at the British Heart Foundation, said:

“We already know that certain aspects of lifestyle increase your risk of heart disease, and we’ve been providing advice on these for many years now.  This study simply adds to the wealth of research already done on this topic.

“There are some lessons we can learn from this study though. It may not be possible for people in the industrialised world to copy the Tsimane community’s way of life, but there are certainly aspects of their diet and lifestyle, such as not smoking and eating a diet low in fat, that we can better incorporate into our lives to help reduce our risk of heart disease.”

 

Dr Amitava Banerjee, Senior Clinical Lecturer in Clinical Data Science and Honorary Consultant Cardiologist, UCL, said:

“This is a high-quality observational study of risk factors for cardiovascular disease and coronary artery calcium scores, which are an accurate way of looking at coronary atherosclerosis: the ‘furring up of the arteries’ which leads eventually to heart attacks.  The authors compared coronary calcium scores in a Bolivian indigenous Tsimane community which lives in pre-industrial conditions (hunting, gathering, fishing and farming), with a contemporary American population.  They found the lowest levels of coronary atherosclerosis found in any human population to-date: five times less than the American population in adults over the age of 75 years, with extremely low levels of risk factors such as hypertension, cholesterol and diabetes.

“This study adds to the evidence base that ‘ideal cardiovascular health’ over a lifetime in terms of low blood pressure, low cholesterol, low blood glucose, normal body-mass index (BMI) and high levels of physical activity can largely prevent coronary atherosclerosis.  Further analysis of this Bolivian community’s lifestyle is required to determine which of these factors or combinations of factors is most important in reducing the future risk of heart disease.

“The Tsimane diet is largely based on unprocessed carbohydrates and low in fat, in contrast to so-called Western diets which are high in fat and high in refined carbohydrates.  On the basis of this one study, it is hard to recommend any particular diet, and it is definitely not possible to recommend any of the many fad diets which are publicised today.  However, it is clear that a healthy, balanced diet as part of a healthy lifestyle, including exercise and refraining from smoking, leads to a healthy heart in the long run.”

 

Prof. Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:

“This study of a Tsimane people in the Bolivian rainforest shows they have very low rates of atherosclerotic disease which is the underlying cause of coronary heart disease.  They live under relatively primitive conditions – fishing, hunter gathering and growing their own food.  The novelty of the study is its use of a scanning technique that measures arterial calcification in the coronary arteries.  It is well known that arteries stiffen with age and this is more likely to occur in arteries affected by atherosclerosis.  Atherosclerosis develops over several decades from early adult life but stiffening occurs much later.  In the developed world arterial stiffening seems to accelerate beyond the age of 60 years of age.  Arterial stiffening is strongly associated with raised blood pressure and it is notable that blood pressure is low lifelong in this group.  Unfortunately, no information is presented on salt intake in this study.  However, other South American tribes such as Yanomami in the Amazon rainforest have been shown to have very low intakes of salt and low blood pressure.  The heavy rainfall in tropical rain forests tends to wash the salt out of the soil.

“Blood cholesterol levels were also low in the Tsimane people which would be consistent with low intakes of saturated fat and high levels of physical activity.  There is limited information on how dietary intake was assessed and the intakes of fat seem much lower than expected for a group consuming fish, wild animals and nuts.  The diet was reported to be very high in carbohydrates.  However, the men had relatively high proportions of body fat – about 22%, where the expected range would be closer to 10-15%.  As body fat is derived mainly from dietary fat, I suspect fat intake from fish, games and nuts may have been under-estimated.  The authors suggest that their lower blood cholesterol concentrations may be part of the explanation for their lower levels of arterial calcification.  Lowering blood cholesterol reduces lipid deposits in arteries but calcification of arteries probably involves a different mechanism.  Indeed, drugs such as statins that lower blood cholesterol concentration tend to increase rather than reduce arterial calcification.

“The high levels of physical activity probably contribute to the lower rate of stiffening as ‘arterial stretching’ helps maintain healthy arteries.  The lack of type 2 diabetes and lack of elevated blood sugar levels in the Tsimane may also be another reason, because glycation (reaction with glucose) of proteins in the artery wall can contribute to stiffening.  Although there are several aspects of the Tsimane people’s lifestyle (including low levels of tobacco use) that seem positive with regard to risk of cardiovascular disease, it is to be noted that the most common age of death (modal) was only 70 compared with over 80 years in the UK.  Furthermore, both the men and women were stunted with average height of men being 1.55 m (5 ft 1 inch).  Life-expectancy at birth is much lower in communities such as these than in developed economies because of high rates of maternal mortality in pregnancy (as high as 10%) and infant mortality (about 20% of children die in first five years of life) as well as a high death rate from infectious disease in adults.”

 

Dr Gunter Kuhnle, Associate Professor in Nutrition and Health, University of Reading, said:

“These kinds of studies have a long history of providing unique insights into risk factors of disease.  While such anthropological investigations are usually not sufficient to confirm or reject hypothesis, they definitely contribute to the body of evidence available.

“The study is very interesting: not because it supports current advice to prevent cardiovascular diseases (low saturated fat intake, regular exercise) but because it clearly shows that in this group very high carbohydrate intake (much higher than in the UK) is not associated with increased heart disease risk – something that has been regularly claimed recently.

“There are of course numerous limitations: the study is cross-sectional and there are many factors involved in heart disease risk – the study design makes it impossible to identify a single one.  But the data are extremely useful to inform further research.”

 

Prof. Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said:

“This is a beautiful real life study which reaffirms all we understand about preventing heart disease.  Simply put, eating a healthy diet very low in saturated fat and full of unprocessed products, not smoking and being active life long, is associated with the lowest risk of having furring up of blood vessels in the heart and the lowest risk of heart disease.  As such this study provides strong support for well-known health messages but in striking way.”

 

Prof. David Thurnham, Emeritus Professor of Human Nutrition, University of Ulster, said:

“A very interesting paper showing a very low risk of coronary atherosclerosis associated with a subsistence lifestyle in Bolivian Tsimane people.  Lifestyle factors examined included hunting, gathering, fishing and farming and this was accompanied by a high infectious inflammatory burden.

“In more sedentary populations inflammation is suggested to be a contributor to atherosclerosis risk but there was no association between the inflammatory biomarkers and low blood HDL or LDL cholesterol concentrations in these people in whom obesity, hypertension, high blood sugar and smoking were rare.

“A factor which was not mentioned in this paper was the vegetable intake.  No information was given or what was ‘gathered’ and no mention on what was farmed apart from manioc (a starchy tuberous root rich in carbohydrate).  At the start of 2016, Leermakers reported a systematic review of the literature on lutein and its beneficial associations with cardiometabolic health1.  The carotenoid lutein is a good biomarkers of vegetable intake and our own work has shown that plasma lutein concentration were very high French people living in Toulouse where the risk of atherosclerosis was among the lowest in the Western world2.  Lutein is a yellow pigment with antioxidant properties and widely distributed in green plant material and also the yolk of eggs and some fruits.

“The lack of information on the vegetable intake of the Tsimane people is unfortunate in what is otherwise a very interesting piece of work.”

  1. Leermakers ET, Darweesh SK, Baena CP et al. The effects of lutein on cardiometabolic health across the life course: a systematic review and meta-analysis. Am J Clin Nutr 2016; 103:481-494.
  1. Howard AN, Thurnham DI. Lutein and atherosclerosis: Belfast versus Toulouse revisited. Med Hypoth 2017; 98:63-68.

 

Dr Gavin Sandercock, Reader in Clinical Physiology (Cardiology) and Director of Research, University of Essex, said:

“This is an excellent study with unique findings.  The Tsimane get 72% of their energy from carbohydrates.  The fact that they have the best indicators of cardiovascular health ever reported is the exact opposite to many recent suggestions that carbohydrates are unhealthy.  The study findings strongly support the long-standing recommendations to get around 65% of our energy from carbohydrates.

“There are problems generalising the study findings to inform healthy lifestyles in developed countries.  The Tsimane lifestyle is like that of our ancestors and their living conditions much more like those which shaped our evolution.  While their dietary intake is not dissimilar to many westerners their physical activity habits could not be more different.

“Like our ancestors they are active most of the day – neither do they sit for prolonged periods.  Sedentary activities (those that require a sitting posture) are relatively modern human behaviours.  While they are active for 5-7 hours each day, the Tsimane don’t appear to ‘exercise’ or train like athletes or gym-users in developed countries do; sport is also a relatively recent human behaviour.  The findings highlight the benefits of habitual activity, particularly staying active in older age.

“Although they live to 70 (compared with around 80 years in developed countries) it is hard to compare the Tsimane with older adults in the UK.  There may not be many old Tsimane men with heart disease but that’s probably because only the fittest and healthiest Tsimane survive to old age.  This makes the sample of available older Tsimane selective – many might have died in childhood or adulthood of diseases westerners are innoculated against, infection or parasites. These selection pressures have been removed in developed countries.

“The Tsimane lead what we refer to as a ‘high energy flux lifestyle’ (they move a lot and eat a lot – including lots of carbohydrates).  Humans evolved to live like this – but we have engineered much of natural activity out of our lives.  It’s obvious that sitting down all day and driving instead of walking mean we are less active than our hunter-gatherer ancestors.  UK adults eat fewer calories today than ever before (including less sugar) but being inactive is fighting against our evolutionary physiology.  Modern medicine has added many years to life – but prolonged senescence supported by an expensive cocktail of pharmacological aids and medical interventions means our latter years may not provide the quality of life we expect.  Keeping active and eating well can add life to years – and it’s free.”

 

* ‘Coronary atherosclerosis in indigenous South American Tsimane: a cross-sectional cohort study’ by Hillard Kaplan et al. published in The Lancet on Friday 17 March 2017.

 

Declared interests

Dr Tim Chico: “I am a committee member and Treasurer of the British Atherosclerosis Society, a charity established in 1999 to promote UK atherosclerosis research.”

Dr Amitava Banerjee: “No conflicts of interest.”

Prof. Tom Sanders: “Prof Tom Sanders is a Scientific Governor of the charity British Nutrition Foundation, member of the scientific advisory committee of the Natural Hydration Council (which promotes the drinking of water), and honorary Nutritional Director of the charity HEART UK.

Prof Tom Sanders is now emeritus but when he was doing research at King’s College London, the following applied:

Tom does not hold any grants or have any consultancies with companies involved in the production or marketing of sugar-sweetened drinks. In reference to previous funding to Tom’s institution: £4.5 million was donated to King’s College London by Tate & Lyle in 2006; this funding finished in 2011. This money was given to the College and was in recognition of the discovery of the artificial sweetener sucralose by Prof Hough at the Queen Elizabeth College (QEC), which merged with King’s College London. The Tate & Lyle grant paid for the Clinical Research Centre at St Thomas’ that is run by the Guy’s & St Thomas’ Trust, it was not used to fund research on sugar. Tate & Lyle sold their sugar interests to American Sugar so the brand Tate & Lyle still exists but it is no longer linked to the company Tate & Lyle PLC, which gave the money to King’s College London in 2006.

Tom also used to work for Ajinomoto on aspartame about 8 years ago.

Tom was a member of the FAO/WHO Joint Expert Committee that recommended that trans fatty acids be removed from the human food chain.

Tom has previously acted as a member of the Global Dairy Platform Scientific Advisory Panel and Tom is a member of the Programme Advisory Committee of the Malaysian Palm Oil Board.

In the past Tom has acted as a consultant to Archer Daniel Midland Company and received honoraria for meetings sponsored by Unilever PLC.

Tom’s research on fats was funded by Public Health England/Food Standards Agency.”

Dr Gunter Kuhnle: “Associate Professor at the University of Reading.  Grant funding: Investigation of links between polyphenol intake and health – EU, Mars, Horizon.  Appointments: EFSA Working group – risk assessment of soy isoflavones.  Memberships: British Mass Spectrometry Society, British Nutrition Society, Registered Nutritionist (Reg. Nr. 8236); 2011 to 2012 member of ‘Biomarker group’ at ILSI Europe.  Other financial interests: Vineyard owned by family.”

Prof. Naveed Sattar: “NS has consulted for Amgen and Sanofi.”

Prof. David Thurnham: “I do consultancy work for the Howard Foundation (HF). HF is a charity and has financial interests in the beneficial properties of lutein in eye health and dementia.”

Dr Gavin Sandercock: “I have no conflicts of interest to declare.”

None others received.

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