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Reference topic 8: The Heart That Remembers the Savanna

Heart disease and evolution: why the heart needs movement

ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.64 sources8 graded recommendationsTopic hub: Movement

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In 2014 and 2015, 705 Tsimane men and women aged 40 and over left their villages in the Bolivian Amazon to lie, one at a time, inside a CT scanner in the city of Trinidad. The Tsimane, forager-farmers of the Maniqui River, lived without clean water, sewerage or electricity. At any time, more than two-thirds of their adults carried intestinal worms.1 The journey took one to two days by river to the nearest market town, then about six hours by road.2

The study's cardiologists had hunted for heart disease in stranger places: several had spent years scanning mummies for hardened arteries.1 Now they looked in the living, for calcium in the coronary arteries that feed the heart muscle. Calcium there marks atherosclerosis, fatty plaque that narrows and stiffens arteries.

Mismatch card

The system

The heart and blood vessels, a pump built to move large volumes of blood for hours.

What it expects

Hours of light and moderate activity daily, little salt, plenty of potassium, a lean body and low LDL for life.

What it gets

Long sitting, about 11 g of salt a day on the global average, too little potassium, abundant food.

What happens in the gap

Blood pressure that climbs with age, earlier and commoner atherosclerosis, a lower aerobic ceiling; 1.4 billion adults aged 30 to 79 with hypertension.

The handrail

Daily movement and aerobic training (●●●); potassium-rich food and, where safe, potassium-enriched salt (●●●)

Strength of evidence

●●○ Trials firmly link salt, potassium and training to blood pressure and fitness, but population comparisons and the fitness-mortality link are observational.

What this topic covers

  • ·A Pump Built for Volume
  • ·The Aerobic Ceiling
  • ·The Beat Between Beats
  • ·Pressure That Need Not Rise
  • ·The Smokers of Kitava
  • ·Swapping the Salt
  • ·Nagano Measures Its Soup
  • ·The Outboard Motor

The practical version is in the book: Chapter 3, The Body That Walks.

The handrail

Topic 40 holds the full movement program; these points are for the heart.

Each recommendation carries the strength of the evidence behind it. How the grades work.

  1. Move through the day, every day

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Use the step and weekly-minute targets in Topic 40; the Tsimane pattern is hours of mostly light and moderate activity.5

  2. Raise your ceiling

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Evidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism. that training raises VO2 max·Evidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. that this lengthens life

    Steady endurance training and intervals both raise VO2 max, by about 5 mL/kg/min in trials of healthy adults aged 18 to 45, intervals slightly more.59 One tested format: four 4-minute efforts at 90-95% of maximum heart rate, each followed by 3 minutes of easy active recovery, three times a week. In a trial of 40 moderately trained men, it raised VO2 max 7.2% in 8 weeks.60

  3. Eat for potassium

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Build meals on fruit and vegetables, as DASH did, though that diet changed more than potassium.34 WHO suggests at least 3,510 mg of potassium a day from food.61 Avoid potassium supplements unless a clinician prescribes them; at high doses they raised pressure in some trials.35 With kidney disease, or on a medicine that affects potassium, ask your clinician what intake is right for you.

  4. If you salt at home, swap the shaker

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Evidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism. for blood pressure·Evidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials. for strokes and deaths outside rural China

    Potassium-enriched salt (about 25% potassium chloride) lowers systolic pressure by about 4-5 mmHg, and more where kitchens do the salting.3862 Do not use it if you have kidney disease, take potassium-sparing diuretics or potassium supplements, or have any condition or medicine that reduces potassium excretion; ask a clinician first. WHO's guideline does not cover pregnant women or children.3963

  5. Keep salt under 5 g a day

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Evidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism. for blood pressure· the effect on survival is debated

    WHO's limit.28

  6. Know your numbers

    StrongEvidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.

    Some 44% of people with hypertension do not know it.19 Get checked, measure at home if your clinician advises, and never stop blood-pressure medicine on your own.

  7. Treat HRV as a trend, not a target

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    Training raises it; chasing a nightly score is a trap (Topic 43).18

  8. Safety

    Vigorous exertion briefly raises the risk of sudden cardiac death, but the absolute risk is tiny: among 21,481 male physicians, one death per 1.51 million bouts, and less in habitual exercisers.64 Build up gradually. With chest pain, breathlessness out of proportion to effort, fainting, known heart disease or several risk factors, see a clinician before vigorous training.

The skeptic's corner

The case against this topic, from the research itself.

Hardened arteries are not new. Before the Tsimane study, the Horus team CT-scanned 137 mummies spanning more than 4,000 years, from ancient Egypt and Peru to the Ancestral Puebloans and the Unangan hunter-gatherers of the Aleutian Islands. A third had probable or definite atherosclerosis, among them three of the five Unangan. That finding "raises the possibility of a more basic predisposition to the disease."48 The prehistoric Tyrolean Iceman, Ötzi, had calcified arteries too, and a genetic predisposition to coronary heart disease (Topic 4).49

What is new is the epidemic. Only six mummies showed disease in the coronary arteries, and those with atherosclerosis had died older, at 43 on average against 32.48 Heart disease has been America's leading cause of death since 1921.50 After decades of increase, age-adjusted deaths from heart disease and stroke in industrialized countries fell to about a third of their 1960s level by 2000. That was too fast for any change in genes; models credit less smoking and better prevention and treatment.51 In a Dutch family with an inherited form of very high cholesterol, carriers' death rates were normal in the nineteenth century, rose after 1915 and peaked in the mid-twentieth.52

The field evidence has soft spots. Kitava's "absence" of heart disease rests on interviews and resting ECGs, not autopsies or scans; smoking intensity is unclear; and systolic pressure there still rose after 50.323031 Kitava does not show that smoking is safe; at most it suggests that other risks can be low enough to blunt it. The low-salt INTERSALT groups were also lean and drank little alcohol.24 The island Kuna of Panama ate plenty of salt yet kept low blood pressure into old age: salt is not the only lever.53 Nor are the Tsimane free of vascular disease. More than nine in ten Tsimane and Moseten adults studied had calcified arteries inside the skull, a higher share than in comparable industrialized groups.54 And those who reach old age in a hard life may be unusually hardy.

The fixes have caveats too. In trials, cutting salt lowers blood pressure in people with and without hypertension.55 But large cohort studies that estimate intake from one morning urine sample find the lowest risk at moderate sodium intakes, with risk rising at both extremes.56 Critics blame the single sample. One long follow-up with repeated full-day urine collections found mortality rising steadily with sodium, even at the lowest intakes.5755 The links between fitness and long life are observational. A five-year exercise trial in Norwegians in their seventies found no significant effect on deaths, though its control group was itself quite active.58

Terms this topic defines

Related topics

Sources cited above

  1. 1.Kaplan, H., Thompson, R.C., Trumble, B.C., Wann, L.S., et al. (2017). "Coronary atherosclerosis in indigenous South American Tsimane: a cross-sectional cohort study." The Lancet, 389(10080), 1730-1739. https://doi.org/10.1016/S0140-6736(17)30752-3 (Scans ran July 2014 to September 2015; about 16,000 Tsimane lived in villages of 60 to 200 people. Of people over 60 not scanned, 49 had moved after major flooding, 15 were busy hunting, farming or caring for children, and two refused. 596 of 705 had no coronary calcium, 13% scored 1 to 100 and 3% above 100; over 75, 65% had none and 8% scored 100 or more, five times lower than in industrialized populations. Less than 10% of daylight hours sedentary; about 72% of calories from carbohydrate; mean LDL 91 mg/dL at the time of the scans, after averaging 1.84 mmol/L (about 71 mg/dL) in 2004-2011 and rising about 0.16 mmol/L a year after 2011.)
  2. 2.Thompson, D. (2017, 20 March). "Why this Amazon tribe may have the world's healthiest hearts." HealthDay, published by CBS News. https://www.cbsnews.com/news/amazon-tsimane-tribe-diet-lifestyle-habits-healthy-hearts/ (journalistic source; travel times as Gregory Thomas described them).
  3. 48.Thompson, R.C., Allam, A.H., Lombardi, G.P., Wann, L.S., et al. (2013). "Atherosclerosis across 4000 years of human history: the Horus study of four ancient populations." The Lancet, 381(9873), 1211-1222. https://doi.org/10.1016/S0140-6736(13)60598-X (137 mummies; six (4%) with coronary involvement.)
  4. 49.Keller, A., Graefen, A., Ball, M., Matzas, M., et al. (2012). "New insights into the Tyrolean Iceman's origin and phenotype as inferred by whole-genome sequencing." Nature Communications, 3, 698. https://doi.org/10.1038/ncomms1701
  5. 50.Centers for Disease Control and Prevention (1999). "Decline in deaths from heart disease and stroke, United States, 1900-1999." MMWR, 48(30), 649-656. https://pubmed.ncbi.nlm.nih.gov/10488780/
  6. 51.Mensah, G.A., Wei, G.S., Sorlie, P.D., Fine, L.J., et al. (2017). "Decline in cardiovascular mortality: possible causes and implications." Circulation Research, 120(2), 366-380. https://doi.org/10.1161/CIRCRESAHA.116.309115
  7. 52.Sijbrands, E.J., Westendorp, R.G., Defesche, J.C., de Meier, P.H., et al. (2001). "Mortality over two centuries in large pedigree with familial hypercholesterolaemia: family tree mortality study." BMJ, 322(7293), 1019-1023. https://doi.org/10.1136/bmj.322.7293.1019
  8. 32.Lindeberg, S., and Lundh, B. (1993). "Apparent absence of stroke and ischaemic heart disease in a traditional Melanesian island: a clinical study in Kitava." Journal of Internal Medicine, 233(3), 269-275. https://doi.org/10.1111/j.1365-2796.1993.tb00986.x (213 adults aged 20 to 96.)
  9. 30.Carrera-Bastos, P., Fontes-Villalba, M., Gurven, M., Muskiet, F.A.J., et al. (2020). "C-reactive protein in traditional Melanesians on Kitava." BMC Cardiovascular Disorders, 20(1), 524. https://doi.org/10.1186/s12872-020-01812-7 (Mean body mass index 18.9.)
  10. 31.Lindeberg, S., Berntorp, E., Nilsson-Ehle, P., Terént, A., and Vessby, B. (1997). "Age relations of cardiovascular risk factors in a traditional Melanesian society: the Kitava Study." American Journal of Clinical Nutrition, 66(4), 845-852. https://doi.org/10.1093/ajcn/66.4.845
  11. 24.Carvalho, J.J., Baruzzi, R.G., Howard, P.F., Poulter, N., et al. (1989). "Blood pressure in four remote populations in the INTERSALT Study." Hypertension, 14(3), 238-246. https://doi.org/10.1161/01.hyp.14.3.238 (Median salt intake under 1 g to 3 g a day against more than 9 g elsewhere; mean blood pressure 103/63 mmHg against 120/74.)
  12. 53.Hollenberg, N.K., Martinez, G., McCullough, M., Meinking, T., et al. (1997). "Aging, acculturation, salt intake, and hypertension in the Kuna of Panama." Hypertension, 29(1 Pt 2), 171-176. https://doi.org/10.1161/01.hyp.29.1.171
  13. 54.Barisano, G., Bigjahan, B., Schleifer, G., Ashna, M., et al. (2026). "High prevalence of cerebrovascular calcifications and clinical correlates in Indigenous Bolivian forager-horticulturalists." Journal of the American Heart Association, 15(3), e043028. https://doi.org/10.1161/JAHA.125.043028 (1,232 adults; more than 90%.)
  14. 55.He, F.J., Tan, M., Ma, Y., and MacGregor, G.A. (2020). "Salt reduction to prevent hypertension and cardiovascular disease: JACC state-of-the-art review." Journal of the American College of Cardiology, 75(6), 632-647. https://doi.org/10.1016/j.jacc.2019.11.055
  15. 56.O'Donnell, M., Mente, A., Rangarajan, S., McQueen, M.J., et al. (2019). "Joint association of urinary sodium and potassium excretion with cardiovascular events and mortality: prospective cohort study." BMJ, 364, l772. https://doi.org/10.1136/bmj.l772
  16. 57.Cook, N.R., Appel, L.J., and Whelton, P.K. (2016). "Sodium intake and all-cause mortality over 20 years in the Trials of Hypertension Prevention." Journal of the American College of Cardiology, 68(15), 1609-1617. https://doi.org/10.1016/j.jacc.2016.07.745
  17. 58.Stensvold, D., Viken, H., Steinshamn, S.L., Dalen, H., et al. (2020). "Effect of exercise training for five years on all cause mortality in older adults: the Generation 100 study: randomised controlled trial." BMJ, 371, m3485. https://doi.org/10.1136/bmj.m3485 (1,567 participants aged 70 to 77.)
  18. 5.Gurven, M., Jaeggi, A.V., Kaplan, H., and Cummings, D. (2013). "Physical activity and modernization among Bolivian Amerindians." PLoS ONE, 8(1), e55679. https://doi.org/10.1371/journal.pone.0055679
  19. 59.Milanović, Z., Sporiš, G., and Weston, M. (2015). "Effectiveness of high-intensity interval training (HIT) and continuous endurance training for VO2max improvements: a systematic review and meta-analysis of controlled trials." Sports Medicine, 45(10), 1469-1481. https://doi.org/10.1007/s40279-015-0365-0
  20. 60.Helgerud, J., Høydal, K., Wang, E., Karlsen, T., et al. (2007). "Aerobic high-intensity intervals improve VO2max more than moderate training." Medicine and Science in Sports and Exercise, 39(4), 665-671. https://doi.org/10.1249/mss.0b013e3180304570
  21. 34.Appel, L.J., Moore, T.J., Obarzanek, E., Vollmer, W.M., et al. (1997). "A clinical trial of the effects of dietary patterns on blood pressure." New England Journal of Medicine, 336(16), 1117-1124. https://doi.org/10.1056/NEJM199704173361601 (459 adults; 11.4/5.5 mmHg in people with hypertension.)
  22. 61.World Health Organization (2012). Guideline: Potassium intake for adults and children. https://www.ncbi.nlm.nih.gov/books/NBK132458/
  23. 35.Filippini, T., Naska, A., Kasdagli, M.I., Torres, D., et al. (2020). "Potassium intake and blood pressure: a dose-response meta-analysis of randomized controlled trials." Journal of the American Heart Association, 9(12), e015719. https://doi.org/10.1161/JAHA.119.015719 (32 trials; 3.9/2.4 mmHg; benefit weakened above an extra 30 mmol or so a day, and pressure rose above about 80.)
  24. 38.Lai, H., Nesrallah, G., Guyatt, G.H., Vernooij, R.W.M., et al. (2026). "Comparative effects of salt substitutes on blood pressure, cardiovascular events and mortality: a systematic review and network meta-analysis." BMC Medicine, 24(1), 106. https://doi.org/10.1186/s12916-026-04635-z
  25. 62.Zhang, X., Yuan, Y., Gao, C., Yin, X., et al. (2026). "Blood pressure reduction effects of salt substitutes in different application settings: a meta-analysis of randomized controlled trials." JACC: Asia, 6(7), 1148-1158. https://doi.org/10.1016/j.jacasi.2026.02.014
  26. 39.World Health Organization (2025). Use of lower-sodium salt substitutes: WHO guideline. https://www.ncbi.nlm.nih.gov/books/NBK612035/
  27. 63.Xu, X., Zeng, L., Jha, V., Cobb, L.K., et al. (2024). "Potassium-enriched salt substitutes: a review of recommendations in clinical management guidelines." Hypertension, 81(3), 400-414. https://doi.org/10.1161/HYPERTENSIONAHA.123.21343
  28. 28.World Health Organization (2026). Sodium reduction (fact sheet, updated 11 May 2026). https://www.who.int/news-room/fact-sheets/detail/sodium-reduction (2021 estimate.)
  29. 19.World Health Organization (2025). Hypertension (fact sheet, updated 25 September 2025). https://www.who.int/news-room/fact-sheets/detail/hypertension; World Health Organization (2025). Global report on hypertension 2025: high stakes, turning evidence into action (launch news release, 23 September 2025). https://www.who.int/news/item/23-09-2025-uncontrolled-high-blood-pressure-puts-over-a-billion-people-at-risk (1.4 billion adults in 2024, two-thirds in low- and middle-income countries; about 44% unaware; 23% controlled.)
  30. 18.Sandercock, G.R., Bromley, P.D., and Brodie, D.A. (2005). "Effects of exercise on heart rate variability: inferences from meta-analysis." Medicine and Science in Sports and Exercise, 37(3), 433-439. https://doi.org/10.1249/01.mss.0000155388.39002.9d
  31. 64.Albert, C.M., Mittleman, M.A., Chae, C.U., Lee, I.M., et al. (2000). "Triggering of sudden death from cardiac causes by vigorous exertion." New England Journal of Medicine, 343(19), 1355-1361. https://doi.org/10.1056/NEJM200011093431902

This topic carries 64 notes in the research manuscript; the 31 above are those behind the material on this page. Full source register.