Kitava: Wrapping it Up

There's a lot to be learned from the Kitava study. Kitavans eat a diet of root vegetables, coconut, fruit, vegetables and fish and have undetectable levels of cardiovascular disease (CVD), stroke and overweight. Despite light smoking. 69% of their calories come from carbohydrate, 21% from fat and 10% from protein. This is essentially a carbohydrate-heavy version of what our paleolithic ancestors ate. They also get lots of sunshine and have a moderately high activity level.

The first thing we can say is that a high intake of carbohydrate is not enough, by itself, to cause overweight or the diseases of civilization. It's also not enough to cause insulin resistance. I sent an e-mail to Dr. Lindeberg asking if his group had measured Kitavans' glucose tolerance. He told me they had not. However, I can only guess they had good glucose control since they suffered from none of the complications of unmanaged diabetes.

The Kitavan diet is low in fat, and most of the fat they eat is saturated because it comes from coconuts. Compared to Americans and Swedes, they have a high intake of saturated fat. So much for the theory that saturated fat causes CVD... They also have a relatively high intake of fish fat, at 4g per day. This gives them a high ratio of omega-3 to omega-6 fatty acids, with plenty of DHA and EPA.

Their blood lipid profile is not what a mainstream cardiologist would expect. In fact, it's "worse" than the Swedish profile in many ways, despite the fact that Swedes are highly prone to CVD. This raises the possibility that blood lipids are not causing CVD, but are simply markers of diet and lifestyle factors. That's very easy for me to swallow because it never made sense to me that our livers would try to kill us by secreting triglycerides and withholding HDL. The blood lipid profile that associates best with CVD and metabolic syndrome in the West (but has no relation to them on Kitava) is one that's consistent with a high carbohydrate intake. Where does carbohydrate come from in the West? White flour and sugar maybe?

Kitavans also have very low serum leptin. This may be a keystone to their leanness and health. It suggests that their diet is not interfering with the body's metabolic feedback loops that maintain leanness.

The Kitavan diet is one path to vibrant health. Like many other non-industrial groups, Kitavans eat whole, natural foods that are broadly consistent with what our hunter-gatherer ancestors would have eaten. It amazes me that as humans, we can live well on diets that range from near-complete carnivory to plant-rich omnivory. We are possibly the most adaptable species on the planet.

The ideal diet for humans includes a lot of possibilities. I believe the focus on macronutrients is misguided. There are examples of cultures that were/are healthy eating high-fat diets, high-carbohydrate diets and everything in between. What they do not eat is processed grains, particularly wheat, refined sugar, industrially processed seed oils and other modern foods. I believe these are unhealthy, and this is visible in the trail of destruction they have left around the globe. Its traces can be found in the Pacific islands, where close genetic relatives of the Kitavans have become morbidly obese and unhealthy on a processed-food diet.

Cardiovascular Risk Factors on Kitava, Part IV: Leptin

Leptin is a hormone that is a central player in the process of weight gain and chronic disease. Its existence had been predicted for decades, but it was not identified until 1994. Although less well known than insulin, its effects on nutrient disposal, metabolic rate and feeding behaviors place it on the same level of importance.

Caloric intake and expenditure vary from day to day and week to week in humans, yet most people maintain a relatively stable weight without consciously adjusting food intake. For example, I become hungry after a long fast, whereas I won't be very hungry if I've stuffed myself for two meals in a row. This suggests a homeostatic mechanism, or feedback loop, which keeps weight in the body's preferred range. Leptin is the major feedback signal.

Here's how it works. Leptin is secreted by adipose (fat) tissue, and its blood levels are proportional to fat mass. The more fat, the more leptin. It acts in the brain to increase the metabolic rate, decrease eating behaviors, and inhibit the deposition of fat. Thus, if fat mass increases, hunger diminishes and the body tries to burn calories to regain its preferred equilibrium.

The next logical question is "how could anyone become obese if this feedback loop inhibits energy storage in response to fat gain?" The answer is a problem called leptin resistance. In people who are obese, the brain no longer responds to the leptin signal. In fact, the brain believes leptin levels are low, implying stored energy is low, so it thinks it's starving. This explains the low metabolic rate, increased tendency for fat storage and hyperphagia (increased eating) seen in many obese people. Leptin resistance has reset the body's preferred weight 'set-point' to a higher level.

Incidentally, some reaserchers have claimed that obese people gain fat because they don't fidget as much as others. This is based on the observation that thin people fidget more than overweight people. Leptin also influences activity levels, so it's possible that obese people fidget less than thin people due to their leptin resistance. In other words, they fidget less because they're fat, rather than the other way around.

The problem of leptin resistance is well illustrated by a rat model called the Zucker fatty strain. The Zucker rat has a mutation in the leptin receptor gene, making its brain unresponsive to leptin signals. The rat's fat tissue pumps out leptin, but its brain is deaf to it. This is basically a model of severe leptin resistance, the same thing we see in obese humans. What happens to these rats? They become hyperphagic, hypometabolic, obese, develop insulin resistance, impaired glucose tolerance, dyslipidemia, diabetes, and cardiovascular disease. Basically, severe metabolic syndrome.

This shows that leptin resistance is sufficient to cause many of the common metabolic problems that plague modern societies. In humans, it's a little known fact that leptin resistance precedes the development of obesity, insulin resistance, and impaired glucose tolerance! Furthermore, humans with leptin receptor mutations or impaired leptin production become hyperphagic and severely obese. This puts leptin at the top of my list of suspects.

So here we have the Kitavans, who are thin and healthy. How's their leptin? Incredibly low. Even in young individuals, Kitavan leptin levels average less than half of Swedish levels. Beyond age 60, Kitavans have 1/4 the leptin level of Swedish people. The difference is so great, the standard deviations don't even overlap.

This isn't surprising, since leptin levels track with fat mass and the Kitavans are very lean (average male BMI = 20, female BMI = 18). Now we are faced with a chicken and egg question. Are Kitavans thin because they're leptin-sensitive, or are they leptin-sensitive because they're thin?

There's no way to answer this question conclusively using the data I'm familiar with. However, in mice and humans, leptin resistance by itself can initiate a spectrum of metabolic problems very reminiscent of what we see so frequently in modern societies. This leads me to believe that there's something about the modern lifestyle that causes leptin resistance. As usual, my microscope is pointed directly at industrial food.

Cardiovascular Risk Factors on Kitava, Part II: Blood Lipids

The findings in the previous post are all pretty much expected in a population that doesn't get heart disease. However, things started to get interesting when Lindeberg's group measured the Kitavans' serum lipids ("cholesterol"). Kitavan and Swedish total cholesterol is about the same in young men, around 174 mg/dL (4.5 mmol/L). It rises with age in older Swedish men but not Kitavans.

Doctors commonly refer to total cholesterol over 200 mg/dL (5.2 mmol/L) as "high", so Kitavan men are in the clear. On the other hand, Kitavan women should be dying of heart disease left and right with their high middle-age cholesterol of 247 mg/dL (6.4 mmol/L)! That's actually higher than the value for Swedish women of the same age, who are far more prone to heart disease than Kitavans.

The fun doesn't stop there. Total cholesterol isn't a good predictor of heart attack risk, but there are better measures. LDL on Kitava is lower in males than in Sweden, but for females it's about the same until old age.  HDL is slightly lower than Swedes' at middle and old age, and triglycerides are higher on average. Judging by these numbers, Kitavans should have cardiovascular disease (CVD) comparable to Swedes, who suffer from a high rate of cardiovascular mortality.

Kitavan smokers had a lower HDL than nonsmokers, yet still did not develop CVD. Smoking is considered one of the most powerful risk factors for cardiovascular disease in Western populations.  I think it's worth noting, however, that Kitavans tend to be light smokers.

These data are difficult to reconcile with the hypothesis that certain patterns of blood lipids cause CVD. Kitavans, particularly the women, have a blood lipid profile that should have them clutching their chests, yet they remain healthy.

There is a theory of the relationship between blood lipids and CVD that can explain these data. Perhaps blood lipids, rather than causing CVD, simply reflect diet composition and other lifestyle factors. Both on Kitava and in the West, low HDL and elevated triglycerides imply a high carbohydrate intake. Low-carbohydrate diets consistently raise HDL and lower triglycerides. On Kitava, carbohydrate comes mostly from root crops. In the West, it comes mostly from processed grains (typically wheat) and sugar. So the blood lipid pattern that associates best with CVD and the metabolic syndrome in the West is simply a marker of industrial food intake.

Cardiovascular Risk Factors on Kitava, Part I: Weight and Blood Pressure

The Kitavans are an isolated population free of cardiovascular disease and stroke, despite the fact that more than three quarters of them smoke cigarettes (although not very frequently). They eat a carbohydrate-heavy, whole-foods diet that is uninfluenced by modern food habits and consists mostly of starchy root crops, fruit, vegetables, coconut and fish. Their intake of grains and processed foods is negligible.

Naturally, when Dr. Lindeberg's group discovered that Kitavans don't suffer from heart disease or stroke, they investigated further. In the second paper of the series, they analyzed the Kitavans' "cardiovascular risk factors" that sometimes associate with heart disease in Western populations, such as overweight, hypertension, elevated total cholesterol and other blood lipid markers.

Kitavans are lean. Adult male body mass index (BMI) starts out at 22, and diminishes with age. For comparison, Swedes begin at a BMI of 25 and stay that way. Both populations lose muscle mass with age, so Kitavans are staying lean while Swedes are gaining fat. The average American has a BMI of about 28, which is considered overweight and 2 points away from being obese.

Kitavans also have a low blood pressure that rises modestly with age. This is actually a bit surprising to me, since other non-industrial groups like the Kuna do not experience a rise in blood pressure with age. Compared with Swedes, Kitavans' blood pressure is considerably lower at all ages.

In the next post, I'll discuss the Kitavans' blood lipid numbers ("cholesterol"), which challenge current thinking about heart disease risk factors.

The Kitavans: Wisdom from the Pacific Islands

There are very few cultures left on this planet that have not been affected by modern food habits. There are even fewer that have been studied thoroughly. The island of Kitava in Papua New Guinea is host to one such culture, and its inhabitants have many profound things to teach us about diet and health.

The Kitava study, a series of papers produced primarily by Dr. Staffan Lindeberg and his collaborators, offers a glimpse into the nutrition and health of an ancient society, using modern scientific methods. This study is one of the most complete and useful characterizations of the diet and health of a non-industrial society I have come across. It's also the study that created, and ultimately resolved, my cognitive dissonance over the health effects of carbohydrate.

From the photos I've seen, the Kitavans are beautiful people. They have the broad, attractive faces, smooth skin and excellent teeth typical of healthy non-industrial peoples.

Like the Kuna, Kitavans straddle the line between agricultural and hunter-gatherer lifestyles. They eat a diet primarily composed of tubers (yam, sweet potato, taro and cassava), fruit, vegetables, coconut and fish, in order of calories. This is typical of traditional Pacific island cultures, although the relative amounts differ.

Grains, refined sugar, vegetable oils and other processed foods are virtually nonexistent on Kitava. They get an estimated 69% of their calories from carbohydrate, 21% from fat, 17% from saturated fat and 10% from protein. Most of their fat intake is saturated because it comes from coconuts. They have an omega-6 : omega-3 ratio of approximately 1:2. Average caloric intake is 2,200 calories per day (9,200 kJ). By Western standards, their diet is high in carbohydrate, high in saturated fat, low in total fat, a bit low in protein and high in calories.

Now for a few relevant facts before we really start diving in:

• Kitavans are moderately active. They have an activity level comparable to a moderately active Swede, the population to which Dr. Lindeberg draws frequent comparisons.
  


• They have abundant food, and shortage is uncommon.
  


• Their good health is probably not related to genetics, since genetically similar groups in the same region are exquisitely sensitive to the ravages of industrial food. Furthermore, the only Kitavan who moved away from the island to live a modern life is also the only fat Kitavan.
  


• Their life expectancy at birth is estimated at 45 years (includes infant mortality), and life expectancy at age 50 is an additional 25 years. This is remarkable for a culture with limited access to modern medicine.
  


• Over 75% of Kitavans smoke cigarettes, although in small amounts. Even the most isolated societies have their modern vices.

The first study in the series is provocatively titled "Apparent absence of stroke and ischaemic heart disease in a traditional Melanesian island: a clinical study in Kitava." In it, Dr. Lindeberg presents data from interviews and electrocardiograms (ECG) suggesting that heart disease and stroke are absent or extremely rare on Kitava. The inhabitants are entirely unfamiliar with the (characteristic) symptoms of heart attack and stroke, despite the sizable elderly population. This is confirmed by the ECG findings, which indicate remarkable cardiovascular health. It also agrees with data from other traditional cultures in Papua New Guinea. Lindeberg states:

For the whole of PNG, no case of IHD or atherothrombotic stroke has been reported in clinical investigations and autopsy studies among traditionally living Melanesians for more than seven decades, though an increasing number of myocardial infarctions [heart attacks] and angina pectoris in urbanized populations have been reported since the 1960s.

Dementia was not found except in in two young Kitavans, who were born handicapped. The elderly remained sharp until death, including one man who reached 100 years of age. Kitavans are also unfamiliar with external cancers, with the exception of one possible case of breast cancer in an elderly woman.

Overall, Kitavans possess a resistance to degenerative diseases that is baffling to industrialized societies. Not only is this typical of non-industrial cultures, I believe it represents the natural state of existence for Homo sapiens. Like all other animals, humans are healthy and robust when occupying their preferred ecological niche. Our niche happens to be a particularly broad one, ranging from near-complete carnivory to plant-rich omnivory. But it does not include large amounts of industrial foods.

In the next few posts, I'll discuss more specific data about the health of the Kitavans.