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What can people who barely get heart disease teach us?
Heart disease is not a normal part of getting old. Two traditional peoples, on a Pacific island and in the Amazon, have almost none. They eat whole, unprocessed food, stay lean and move all day. Their lives show heart disease can be avoided.
An island without heart attacks
Kitava is a small island in the Trobriand Islands of Papua New Guinea. Around 1990, Swedish doctor Staffan Lindeberg studied its people. They lived on yams, sweet potato, taro, fruit, coconut and fish, and ate almost no Western food.
Lindeberg's team interviewed 213 adults aged 20 to 96 about sudden deaths, chest pain on exertion and signs of stroke, and took heart tracings (ECGs) from 171 of them. Nobody described a case of stroke, sudden cardiac death or angina. The team concluded that stroke and heart disease "appear to be absent" on the island.
Not what you'd expect
Kitavans were no health poster. Around three in four adults smoked, and most of their food was starchy tubers. Yet compared with healthy Swedes, Kitavans had:
- lower diastolic blood pressure, which didn't rise with age;
- lower body weight: everyone over 40 was leaner than the Swedish average;
- total and LDL ("bad") cholesterol 10 to 30% lower in older adults;
- fasting insulin that fell with age. At 50 to 74, Kitavans had half the insulin level of Swedes the same age, a sign their bodies handled sugar far better.
Lindeberg's own reading: leanness and low blood pressure best explain the missing heart disease, and different eating habits may explain both.
The healthiest arteries ever measured
The Tsimane live along rivers in the Bolivian Amazon by hunting, fishing, gathering and farming. Their diet is mostly unprocessed carbohydrate (rice, plantain, cassava, corn), with fish and game, and very little fat. Men spend six to seven hours a day physically active, women four to six.
In 2014 and 2015, researchers gave CT scans of the heart to 705 Tsimane adults aged 40 and over. The scan measures calcium in the heart's arteries, a marker of built-up plaque. Their 2017 report in The Lancet found:
| Result | Tsimane |
|---|---|
| No calcium at all | 85% |
| Score over 100 (significant disease) | 3% |
| Over 75 with no calcium | 65% |
Among people over 75, significant disease was five times less common than in a large US comparison group. The authors called it the lowest level of coronary artery disease of any population recorded. This despite high inflammation from infections and parasites, which usually raises risk.
What the two groups share
The diets differ. What they have in common:
- food eaten close to how it grew, with almost nothing processed or packaged;
- low body weight, blood pressure and blood sugar across a whole lifetime;
- plenty of physical work.
The Tsimane researchers put it this way: most coronary artery disease can be avoided with a lifetime of low LDL cholesterol, low blood pressure, low blood sugar, a normal weight, no smoking and lots of activity. They also said the share each factor contributes is still unknown.
This fits a wider pattern. In 1981, doctors Hubert Trowell and Denis Burkitt gathered evidence from 34 scientists on 25 diseases common in rich countries and rare among hunter-gatherers and village farmers. They named them "Western diseases".
What these studies can't tell you
- Food is one difference among many. Activity, sleep, social life and stress all differ too. Observational studies can't separate them.
- Other risks remain. Both groups live with far more infection than people in rich countries. Half the Tsimane scanned had raised markers of inflammation. The heart findings describe the people who reach middle and old age, not everyone born.
- Small numbers. The Kitava work relies on interviews and ECGs, not autopsies or scans, and a few cases could be missed.
So "eat like a Kitavan and never get heart disease" goes too far. "Heart disease is mostly made, not inherited" is supported.
What you can check
The Tsimane authors list the factors behind their finding, and you can measure each of them:
- Blood pressure. Ask for it at any GP or pharmacy.
- LDL cholesterol and fasting blood sugar: one blood test.
- Waist measurement and weight over time.
- Hours a day spent sitting.
- How much of what you eat comes in a packet with an ingredients list.
Each one you move toward the Kitavan or Tsimane range is a step you can take without moving to an island.
Sources
- Lindeberg, S., & 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. doi.org/10.1111/j.1365-2796.1993.tb00986.x
- Lindeberg, S., Nilsson-Ehle, P., Terént, A., Vessby, B., & Scherstén, B. (1994). Cardiovascular risk factors in a Melanesian population apparently free from stroke and ischaemic heart disease: The Kitava study. Journal of Internal Medicine, 236(3), 331–340. doi.org/10.1111/j.1365-2796.1994.tb00804.x
- Lindeberg, S., Eliasson, M., Lindahl, B., & Ahrén, B. (1999). Low serum insulin in traditional Pacific Islanders: The Kitava study. Metabolism, 48(10), 1216–1219. doi.org/10.1016/s0026-0495(99)90258-5
- Kaplan, H., Thompson, R. C., Trumble, B. C., et al. (2017). Coronary atherosclerosis in indigenous South American Tsimane: A cross-sectional cohort study. The Lancet, 389(10080), 1730–1739. doi.org/10.1016/S0140-6736(17)30752-3
- ScienceDaily. (2017, 17 March). Indigenous South American group has healthiest arteries of all populations yet studied. sciencedaily.com
- Trowell, H. C., & Burkitt, D. P. (Eds.). (1981). Western diseases: Their emergence and prevention. Harvard University Press.