Thoughts on the McDougall Advanced Study Weekend

For those of you who aren't familiar with him, Dr. John McDougall is a doctor and diet/health advocate who recommends a very low fat, high starch, whole food vegan diet to control weight and avoid chronic disease.  He's been at it for a long time, and he's a major figure in the "plant-based diet" community (i.e., a diet including little or no animal foods).

Dr. McDougall invited me to participate in his 3-day Advanced Study Weekend retreat in Santa Rosa, CA.  My job was to give my talk on insulin and obesity, and participate in a panel discussion/debate with Dr. McDougall in which we sorted through issues related to low-carb, Paleo, and the health implications of eating animal foods.  I was glad to receive the invitation, because I don't see myself as a diet partisan, and I believe that my evidence-based information is applicable to a variety of diet styles.  I saw the Weekend as an opportunity to extend my thoughts to a new community, challenge myself, and maybe even learn a thing or two.  It was particularly interesting to compare and contrast the Advanced Study Weekend with the Ancestral Health Symposium, which is more Paleo- and low-carb-friendly.

General Observations

The attendees were a lot older than AHS attendees.  I estimate that most of them were in their 60s, although there were some young people in attendance.

I don't place too much emphasis on peoples' personal appearance at conferences like this.  You don't know what a person's background, genetics, or personal struggles may be, you don't know how closely they adhere to the program, and you don't know to what degree a group of people might be self-selected for particular traits*.  But I will note that Dr. McDougall, his family, and many of the other starch-based/plant-based diet advocates tended to be extremely lean with low fat and muscle mass.  They also tended to have a healthy and energetic appearance and demeanor.  As I would expect, decades of exceptionally high starch intake hasn't made them obese or obviously ill.

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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 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.

Composition of the Hunter-Gatherer Diet

I bumped into a fascinating paper today by Dr. Loren Cordain titled "Plant-Animal Subsistence Ratios and Macronutrient Estimations in Worldwide Hunter-Gatherer Diets." Published in 2000 in the American Journal of Clinical Nutrition, the paper estimates the food sources and macronutrient intakes of historical hunter-gatherers based on data from 229 different groups. Based on the available data, these groups did not suffer from the diseases of civilization. This is typical of hunter-gatherers.

Initial data came from the massive Ethnographic Atlas by Dr. George P. Murdock, and was analyzed further by Cordain and his collaborators. Cordain is a professor at Colorado State University, and a longtime proponent of paleolithic diets for health. He has written extensively about the detrimental effects of grains and other modern foods. Here's his website.

The researchers broke food down into three categories: hunted animal foods, fished animal foods and gathered foods. "Gathered foods" are primarily plants, but include some animal foods as well:

Although in the present analysis we assumed that gathering would only include plant foods, Murdock indicated that gathering activities could also include the collection of small land fauna (insects, invertebrates, small mammals, amphibians, and reptiles); therefore, the compiled data may overestimate the relative contribution of gathered plant foods in the average hunter-gatherer diet.

There are a number of striking things about the data once you sum them up. First of all, diet composition varied widely. Many groups were almost totally carnivorous, with 46 getting over 85% of their calories from hunted foods. However, not a single group out of 229 was vegetarian or vegan. No group got less than 15% of their calories from hunted foods, and only 2 of 229 groups ate 76-85% of their calories from gathered foods (don't forget, "gathered foods" also includes small animals). On average, the hunter-gatherer groups analyzed got about 70% of their calories from hunted foods. This makes the case that meat-heavy omnivory is our preferred ecological niche. However, it also shows that we can thrive on a plant-rich diet containing modest amounts of quality animal foods.

The paper also discusses the nature of the plant foods hunter-gatherers ate. Although they ate a wide variety of plants occasionally, more typically they relied on a small number of staple foods with a high energy density. There's a table in the paper that lists the most commonly eaten plant foods. "Vegetables" are notably underrepresented. The most commonly eaten plant foods are fruit, underground storage organs (tubers, roots, corms, bulbs), nuts and other seeds. Leaves and other low-calorie plant parts were used much less frequently.

The paper also gets into the macronutrient composition of hunter-gatherer diets.  He writes that

...the most plausible... percentages of total energy from the macronutrients would be 19-35% for protein, 22-40% for carbohydrate, and 28-58% for fat.

He derives these numbers from projections based on the average composition of plant foods, and the whole-body composition of representative animal foods (includes organs, marrow, blood etc., which they typically ate). 

However, some groups may have eaten more fat than this.  Natives on the North American Pacific coast rendered fat from fish, seals, bears and whales, using it liberally in their food. Here's an excerpt from The Northwest Coast by James Swan, who spent three years living among the natives of the Washington coast in the 1850s:

About a month after my return from the treaty, a whale was washed ashore on the beach between Toke's Point and Gray's Harbor and all the Indians about the Bay went to get their share... The Indians were camped near by out of the reach of the tide, and were all very busy on my arrival securing the blubber either to carry home to their lodges or boiling it out on the spot, provided they happened to have bladders or barrels to put the oil in. Those who were trying out [rendering] the blubber cut it into strips about two inches wide, one and a half inches thick, and a foot long. These strips were then thrown into a kettle of boiling water, and as the grease tried out it was skimmed off with clam shells and thrown into a tub to cool and settle. It was then carefully skimmed off again and put into the barrels or bladders for use. After the strips of blubber have been boiled, they are hung up in the smoke to dry and are then eaten. I have tried this sort of food but must confess that, like crow meat, "I didn't hanker arter it".

I was very impressed by the paper overall. I think it presents a good, simple model for eating well: eat whole foods that are similar to those that hunter-gatherers would have eaten, including at least 20% of calories from high-quality animal sources. Organs are mandatory, vegetables may not be. Sorry, Grandma.

Cancer in Other Non-Industrialized Cultures

In Cancer, Disease of Civilization (1960), Wilhjalmur Stefansson mentions a few cultures besides the Inuit in which large-scale searches never turned up cancer. Dr. Albert Schweitzer examined over 10,000 traditionally-living natives in Gabon (West Africa) in 1913 and did not find cancer. Later, it became common in the same population as they began "living more and more after the manner of the whites."

In Cancer, its Nature, Cause and Cure (1957), Dr. Alexander Berglas describes the search for cancer among natives in Brazil and Ecuador by Dr. Eugene Payne. He examined approximately 60,000 people over 25 years and found no evidence of cancer.

Sir Robert McCarrison conducted a seven year medical survey among the Hunza, in what is now Northern Pakistan. Among 11,000 people, he did not find a single case of cancer. Their diet consisted of soaked and sprouted grains and beans, fruit, vegetables, grass-fed dairy and a small amount of meat (including organs of course).