What is Cob??

Cob

I've been thinking a lot about natural building lately. Here in the US, we are practically forced into occupying homes that are expensive and destructive to the environment. I met a woman last weekend who lives in a yurt and has an outdoor composting toilet. She paid $3,000 for the yurt, making it a dignified way to live on a low income. She's worried because what she's doing on her own property is illegal. She's living in a safe, efficient, inexpensive structure that is extremely light on the land, an it's illegal under her county building codes.

A conventional home that costs $200,000 may end up costing $400,000- $600,000 including interest paid to the bank and all fees. If you can save money and cut out the bank, you might be able to build your own code-compliant house for $100,000 or less, including the land. It isn't difficult to see the financial advantage of building yourself.

Conventional homes are also highly destructive to the environment, partly due to materials and partly due to inefficiency of the completed structure. As usual, I'm looking for alternatives.

One possibility that has caught my imagination is a material called cob. It's made of sand, clay and straw that's mixed together and allowed to harden into a durable monolithic structure. It's a traditional form of construction throughout the world, but the word comes from the UK, where thousands of cob buildings are still standing after up to 500 years. It's similar to adobe, except bricks are not used.

Cob uses inexpensive materials that can typically be gathered on-site or nearby, and have a low embodied energy. The straw is an agricultural waste product and is very inexpensive. Building with cob doesn't require much skill or strength. It can produce highly efficient structures in appropriate climates due to its high thermal mass. It's also extremely durable if cared for properly. Cob has all the attributes of an effective vernacular building technique.

It's also not code-compliant in most places in the US, but that may change as it becomes more familiar. That's also a reason why I'm considering alternatives like strawbale and timberframe construction. It's possible to build code-compliant cob houses in the UK.

Last weekend I went to a "Basics of Cob" workshop at the Ancient Earth school of natural building on Whidbey island. We learned how to mix cob and then we built a bench out of it. The bench will eventually be coated in a smooth earthen or lime plaster. Cob is an amazing material. It's sculptable when wet, but becomes very hard when it dries. It's compatible with a number of other natural building techniques like strawbale and light straw-clay. It really is at the intersection of construction and sculpting. When you build with cob, you aren't limited to straight lines and right angles, so you can create spaces that are highly functional and aesthetic, while also being space-efficient. Here are some photos from the workshop:

Cigarette Smoking

Cigarette Smoking-- Another Factor in the Obesity Epidemic

Obesity rates in the US have more than doubled in the last 30 years, and rates of childhood obesity and extreme adult obesity have tripled.  One third of US adults are considered obese, and another third overweight.  This is the "obesity epidemic".

The obesity epidemic has coincided with significant changes in the US diet, which are clearly involved.  However, there's another probable contributor that's often overlooked: declining smoking rates.  

Here's a graph of cigarette consumption over the last century in the US (1):

You can see that cigarette smoking has declined quite a bit since its peak in 1963-- a decrease of 63 percent to be exact.  It didn't start declining in earnest until 1976 however-- just before the obesity epidemic began.

How Does is Work? 

The main active ingredient in cigarettes is nicotine.  Nicotine acts by binding to a specific type of receptor on neurons (nerve cells) called the nicotinic acetylcholine receptor.  Acetylcholine is one of the main signaling molecules (neurotransmitters) that neurons use to communicate with one another.  Nicotine suppresses food intake, increases energy expenditure, and lowers body fatness.  Smokers tend to be leaner than non-smokers, even though they usually have a cluster of unhealthy lifestyle habits (2, 3), and they rapidly gain weight when they quit (4, 5).  Administering nicotine to rodents under controlled conditions also reduces food intake and body weight substantially (6).

Since the brain (and particularly the hypothalamus) is the organ in charge of regulating food intake and body fatness, one might guess that nicotine acts there either directly or indirectly.  As predicted, nicotine infused directly into the hypothalamus reduces food intake (7), and a recent high-impact paper demonstrated in mice that nicotine exerts its effects on food intake primarily via POMC cells, a type of neuron in the hypothalamus that is important for the regulation of food intake and body fatness (8). 

Have Declining Smoking Rates Contributed to the Obesity Epidemic?

Public health authorities have been waging a war on cigarette smoking since it was firmly established as a risk factor for a number of serious conditions (e.g., cancer and heart attacks)*.  There's no doubt that regularly smoking cigarettes is bad for your health-- in fact it's probably one of the most unhealthy habits there is.  However, smoking kept us leaner than we should have been in the 1950s, 1960s, and 1970s, likely preventing the gradual changes in the US diet and lifestyle from exerting their full effect on our waistline.  As the appetite suppressive effects of cigarettes went away, and our diet became increasingly commercialized, per capita daily calorie intake increased by about 20 percent, and the adult obesity rate doubled.

Here's a graph that I find striking (based on CDC and NHANES data):

Notice that the plateaus (1960 to late 70s) and the steepest slopes (late 70s to 2006) line up almost perfectly.


* My grandmother quit smoking cold turkey in the late 1970s.  When I asked her why, she said "because I found out it was bad for me".

The Tokelau Island Migrant Study: Background and Overview

The Tokelau Island Migrant Study: Background and Overview

Tokelau's troubles began in 1765 with its 'discovery' by British commodore John Byron. Traditionally, residents of the three small coral atolls collectively called Tokelau (Nukunonu, Fakaofo and Atafu) lived an isolated subsistence lifestyle, relying almost exclusively on coconut, seafood, wild fowl and fruit for food. The first reliable account of the Tokelauan population, by an American expedition in 1841, found the people there healthy and happy. Here's an excerpt from Migration and Health in a Small Society: the Case of Tokelau (1992):

The expedition considered the people living there to be healthy and handsome... They all appeared to be thriving on their 'meager diet' of fish and coconut, for no evidence of cultivation was seen... People of both sexes were tattooed with geometric designs and figures of turtles and fish. The numerous reports and journals of the Expedition leave the impression of a generally admirable people - amiable (though cautious), peaceful, orderly, and resourceful.

Between 1841 and 1863, the population of Tokelau was reduced to a fraction of its original size by epidemics and kidnapping by slave ships. The old social and religious order was broken, and the inhabitants were converted to Christianity by overzealous and competing Protestant and Catholic missionaries. During this time, Tokelauans also gained new food sources from other Polynesian islands, including breadfruit trees, pulaka (a starchy tuber), pigs and chickens. Breadfruit is a starchy fruit used like plantain.

Tokelau became a territory of New Zealand in 1925, and Tokelauans were granted New Zealand citizenship in 1948. In 1963, a government-assisted migration program was established to (voluntarily) bring Tokelauans to the New Zealand mainland, as the population of Tokelau had reached a cozy 1,870 people. When a cyclone devastated coconut and breadfruit crops in 1966, Tokelauans began taking advantage of the assisted migration program in earnest. By 1971, roughly half of Tokelauans lived on the New Zealand mainland.

There are two reasons why the Tokelau Island Migrant study is unique. First, it's one of the best-documented transitions from a traditional to a modern lifestyle, studied over decades on Tokelau and in New Zealand. Regular visits by physicians recorded the health of the population as it shifted from a relatively traditional diet to a more Western one. The second thing that makes this population unique is they traditionally have an extraordinarily high saturated fat intake from coconut. They derive between 54 and 62 percent of their calories from coconut, which is 87% saturated. This gives them perhaps the highest documented saturated fat intake in the world. This will be a test of the "diet-heart hypothesis", the idea that dietary fat, cholesterol and especially saturated fat contribute to cardiovascular disease!

Through the late 1960s, cargo ships visited Tokelau every three months, making only small contributions to the islanders' diets. In 1968, just two percent of Tokelauans' calories came from sugar. By 1978, the number had risen to 8 percent, and by 1982, 14 percent. The increase came chiefly from refined sugar and sweetened imported foods. In 1961, ships brought 12 lb of flour per person per year to Tokelau, increasing to 60 lb per year by 1980. During this time, importation of low-quality canned meats such as "mutton flaps" and chicken backs, and sweets also increased. Rice imports declined in the 1970s. The diet of migrants to New Zealand rapidly became highly Westernized, containing a higher proportion of refined carbohydrates such as flour and sugar, more red meat and poultry, and less coconut and seafood.

Here's a nice quote from Migration and Health in a Small Society: the Case of Tokelau, to set the tone for the rest of the posts in this series:

In the mid- and late twentieth century, 'Western diseases'- that is, diseases of affluence (Trowell and Burkitt 1981)- have become the major health risk for Polynesians, because of exposure to cosmopolitan diet patterns and life-style.
The varying cultures and resource bases of islands in the Pacific have influenced the degree to which their populations have been modernized and thus exposed to Western diseases. At one end of the spectrum are relatively traditional subsistence societies such as those on Tokelau and on the low islands- for example Pukapuka, Manihiki, and Rakahanga in the Northern Cook Islands. These atolls are characterized by the almost complete absence of soil, by the inhabitants' dependence on coconut in varied forms, and by a bountiful supply of fish as a major part of the traditional diet. Their populations are notable for their low levels of blood pressure, high rates of infectious disease, and low rates of coronary heart disease, obesity and diabetes. At the other end of the spectrum are those Polynesian societies, such as the Hawaiians and the Maori of New Zealand, who were submerged by 'Western' settlers and the dominating cultures they brought with them. These populations have inevitably acquired the diseases of the 'West', sometimes to an exaggerated degree.

That quote could have been straight out of Nutrition and Physical Degeneration, despite being published 60 years later. Good science is timeless. Join me in future posts as I explore the health of Tokelauan society as it transitions from a traditional diet and lifestyle to a modern one.

Dental Health

The Tokelau Island Migrant Study: Dental Health

I'm always on the lookout for studies that can confirm or deny the information in Nutrition and Physical Degeneration. Traveling around the world in the 1920s and 1930s, Dr. Weston Price found a number of non-industrial cultures that had excellent dental and overall health, including a high resistance to tooth decay, perfectly straight teeth, and wisdom teeth that erupted without impacting. These same cultures developed extreme dental problems, including severe dental decay and crooked teeth in the younger generation, upon adopting modern European foods. These foods always included white flour and refined sugar, with variable contributions from canned goods and vegetable oils.

I have detailed information on the Tokelauan diet beginning in 1968 and ending in 1982. The traditional diet until the 1960s consisted of coconut, fish, breadfruit, pulaka, fruit, pigs, chickens and wild fowl. These are typical Polynesian foods. From the 1960s through the 1980s, Tokelauans gradually adopted flour and sugar as major carbohydrate sources, partially displacing starchy breadfruit and pulaka intake as well as coconut. They also began eating low-quality canned meats that partially replaced fish in their diet. Total calorie intake fluctuated between 1,500 and 2,000 kilocalories but did not trend in any particular direction over time. Here's a graph of macronutrient changes:


I found a study on the dental health of Tokelauans that I thought would be a fitting way to kick off this series. It's titled "Changed oral conditions, between 1963 and 1999, in the population of the Tokelau atolls of the South Pacific". I was only able to get my hands on the abstract, but that was enough. In 1963, Tokelauans were consuming roughly 15 lb of white flour and 10 lb of sugar per person per year. By 1980, the numbers were 60 lb and 69 lb for flour and sugar, and the trend was showing no sign of slowing down (see the graph in the previous post). I don't have numbers for 1999, but they're likely to be higher than in 1980, given the trend. For comparison, in 2006, the average American ate 117 lb of flour per year.

Let's look at a graph. This represents the DMF score (decayed, missing or filled teeth) of Tokelauans 15-19 and 35-44 years old, in 1963 and 1999. I've connected the two data points with lines to give an idea of the trend.

Dental decay increased eight-fold in adolescents and more than four-fold in adults. I don't know what their dental health was like before 1963, but I can only guess it was better than when this study was conducted, due to the fact that the Tokelauan diet was already partially modernized in 1963. The authors conclude "a serious decline in oral health has occurred over the past 35 years."

Does this sound familiar? It should be, because it's been known at least since the 1930s. Here's a quote from Nutrition and Physical Degeneration, describing the Tongan islanders, another Polynesian group: 

The limited importation of foods to the Tongan Islands due to the infrequent call of merchant or trading ships has required the people to remain largely on their native foods. Following the war, however, the price of copra went up from $40.00 per ton to $400.00, which brought trading ships with white flour and sugar to exchange for the copra. The effect of this is shown very clearly in the condition of the teeth. The incidence of dental caries [cavities] among the isolated groups living on native foods was 0.6 per cent, while for those around the port living in part on trade foods, it is 33.4 per cent. The effect of the imported food was clearly to be seen on the teeth of the people who were in the growth stage at that time [i.e., they developed crooked teeth]. Now the trader ships no longer call and this forced isolation is very clearly a blessing in disguise. Dental caries has largely ceased to be active since imported foods became scarce, for the price of copra fell to $4.00 a ton. The temporary rise in tooth decay was apparently directly associated with the calling of trader ships.

0.6 percent is one tooth in every 167. In other words, less than one in five people had even a single cavity. That's without the benefit of tooth brushing, fluoride or any of the tools of modern dentistry. 33.4 percent tooth decay in Tongans living on modern foods means they had 11 cavities per person, a bit less than Tokelauans had in 1999. 

Weston Price's anecdote above is remarkably similar to something that happened on Tokelau in 1979. The atolls didn't receive their normal shipments of European foods for a five-month period, during which they resorted to traditional foods. Here's an excerpt from the New Zealand Herald from June 11, 1979:

What will happen the day the country runs out of fuel and the ships stop bringing those "essential" foods like sugar and flour? Tokelauans recently found out what the answer to that question was- they got healthier. One of the victims of cyclone Meli earlier this year was the passenger cargo ship Cenpac Rounder, chartered five times per year by the Tokelau Affairs office in Apia. Left high and dry on a reef South of Fiji it was badly damaged and could not be moved. So ever since January the three Tokelau atolls have not received fresh supplies. Late last month the first ship called in, chartered by the Tokelau Affairs office. The Secretary of the office said that when the ship arrived the atolls had run out of fuel. So the fishermen had returned to the traditional sail, a sight on the lagoon that had almost been forgotten, thanks to the outboard motor. There was no sugar, flour, tobacco and starch foods either- and the atoll hospitals reported a shortage of business during the enforced isolation. It was reported that the Tokelauans had been very healthy during that time and had returned to the pre-European diet of coconuts and fish. Many people lost weight and felt very much better including some of the diabetics.

Cholesterol and Cardiovascular Health

The Tokelau Island Migrant Study: Cholesterol and Cardiovascular Health

Let's get right to the meat of this study. It's relevant to the hypothesis that saturated fat is a cause of cardiovascular disease.  Tokelauans traditionally obtained 40-50% of their calories from saturated fat, in the form of coconut meat. That's more than any other group I'm aware of.

So are the Tokelauans dropping like flies of cardiovascular disease?  I don't have access to the best data of all: actual heart attack incidence data. But we do have some telltale markers. In 1971-1982, researchers collected data from Tokelau and Tokelauan migrants to New Zealand on cholesterol levels, blood pressure and electrocardiogram (ECG) readings. 

The Tokelauan diet, as I've described in detail in previous posts, is traditionally based on coconut, fish, starchy tubers and fruit. By 1982, their diet also contained a significant amount of imported flour and sugar. Migrants to New Zealand had a much more varied diet that was also more typically Western: more carbohydrate, coming chiefly from wheat, sugar and potatoes; more processed sweet foods and drinks; more red meat; more vegetables; more dairy and eggs. Sugar intake was 13 percent of calories, compared to 8 percent on Tokelau. Saturated fat intake in NZ was half of what it was on Tokelau, while total fat intake was similar. Polyunsaturated fat intake was higher in NZ, 4% as opposed to 2% in Tokelau. I don't have data to back this up, but I think it's likely that the n-6:n-3 ratio increased upon migration.

Blood pressure did not change significantly over time in Tokelau from 1971 to 1982, if anything it actually declined slightly. It was consistently higher in NZ than in Tokelau at all timepoints. Men were roughly three times more likely to be hypertensive in NZ than on Tokelau at all timepoints (4.0% vs. 12.0% in the early 1970s). Women were about twice as likely to be hypertensive (8.1% vs. 15.0%).

On to cholesterol. Total cholesterol in male Tokelauans was a bit lower on average than in New Zealand, but neither was particularly elevated (182 vs. 199 mg/dL). LDL was also a bit higher in NZ males (119 vs. 132 mg/dL). Triglycerides were lower in Tokelauan men than in NZ (80 vs. 114 mg/dL). There were no differences in total cholesterol, LDL cholesterol or triglycerides between Tokelauan and NZ women.  It's interesting that serum lipids don't correspond at all to saturated fat intake.

But does it cause heart attacks? The best data I have from this study are ECG readings. These use electrodes to monitor the electrical activity of the heart. There are certain ECG patterns that suggest that a person has had a heart attack (Minnesota codes 1-1 and 1-2). The data I am going to present here are all age-standardized, meaning they are comparing between groups of the same age. On Tokelau in 1982, 0.0% of men 40-69 years old showed ECG readings that indicated a probable past heart attack. In NZ in 1980-81, 1.0% of men 40-69 years old showed the same ECG readings. In Tecumseh U.S.A. in 1965, 3.5% of men 40-69 years old showed the same ECG pattern. I don't have data for women.

These data don't prove that no one ever has a heart attack on Tokelau. Tokelauans do have heart attacks sometimes, and they also have strokes (at least in modern times). But they do allow us to compare in quantitative terms between genetically similar people living in two different environments. 

This is consistent with what has been observed on Kitava and other traditional Pacific island cultures: a vanishingly small incidence of cardiovascular disease while they retain their traditional diet and lifestyle (and sometimes even when some processed Western food has been introduced). When diets and lifestyles become modern, there is invariably a rise in the incidence of chronic disease.

These data raise serious questions about the role of saturated fat in cardiovascular disease. Tokelau underlines the fact that a non-industrial diet and lifestyle may be a more significant protective factor than the quality of ingested fat.

Unless otherwise noted, the data in this post are from the book Migration and Health in a Small Society: the Case of Tokelau.

Weight Gain

The Tokelau Island Migrant Study: Weight Gain

Between 1968 and 1982, Tokelauans in nearly all age groups gained weight, roughly 5 kilograms (11 pounds) on average. They also became slightly taller, but not enough to offset the gain in weight. By 1980-82, migrants to New Zealand had become especially heavy, with all age groups weighing more than non-migrants by about 5 kg (11 lb) on average, and 10 kg (22 lb) more than Tokelauans did in 1968. 

The body mass index (BMI) is a rough estimate of fat mass (although it can be confounded by muscle mass), and is the weight in kilograms divided by the square of the height in meters [BMI = weight / (height^2)]. A BMI of 25 to 30 is considered overweight; 30 and over is considered obese.

The graphs I'm about to present require some explanation. The data in each graph were collected from the same individuals over time (15-69 years old). That means some weight gain is expected, as this population normally gains weight into middle age (then loses weight). What's interesting to note is the difference in the rate of weight change between migrants and non-migrants. The first two data points in 1968 are baseline, and compare non-migrants with "pre-migrants" still living on Tokelau. The second two data points in 1981-82 compare the same individual migrants in New Zealand with the same non-migrants.
Unless they all decided to become body builders, migrants to New Zealand gained more fat mass than Tokelauans between 1968 and 1982. The rate of weight gain in New Zealand was more than twice as fast for men and more than 50% faster for women than on Tokelau. 

Why did Tokelauans and especially migrants to New Zealand gain weight?  Probably because they had greater access to a wide variety of calorie-dense, palatable foods of modern commerce.  The introduction of wheat and sugar, at the expense of coconut and traditional carbohydrate sources, was the main change to the Tokelauan diet during this time period. See this post for a graph.

Finally, there's the question of exercise. Did a change in energy expenditure contribute to weight gain? The study didn't collect data on exercise during the time period in question, so all we have are anecdotes. During this time, men living on Tokelau progressively adopted outboard motors for their fishing boats, replacing the traditional sails and oars. Their energy expenditure probably decreased.

But what about women? Tokelauan women traditionally perform household tasks such as weaving mats and preparing food. Their energy expenditure probably didn't change much over the same time period. Since both men and women on Tokelau gained weight, it would be hard to argue that exercise was a dominant factor.

How about migrants to New Zealand? Here's a quote from Migration and Health in a Small Society: the Case of Tokelau:

Overall it is our belief that most of the migrants expend greater energy in their work than is currently the case in Tokelau.

Exercise doesn't appear to have been the main factor, although the data don't allow us to be totally confident about this.

The Tokelau Island Migrant Study: Diabetes

The Tokelau Island Migrant Study: Diabetes

This post will be short and sweet. Diabetes is a disease of civilization. As Tokelauans adopted Western industrial foods, their diabetes prevalence increased. At any given time point, age-standardized diabetes prevalence was higher in migrants to New Zealand than those who remained on Tokelau:


This is not a difference in diagnosis. Tokelauans were examined for diabetes by the same group of physicians, using the same criteria. It's also not a difference in average age, sice the numbers are age-standardized. On Tokelau, diabetes prevalence doubled in a decade. Migrants to New Zealand in 1981 had roughly three times the prevalence of diabetes that Tokelauans did in 1971. I can only imagine the prevalence is even higher in 2008.

We don't know what the prevalence was in Tokelauans when their diet was completely traditional, but I would expect it to be low like other traditional Pacific island societies. I'm looking at a table right now of age-standardized diabetes prevalence on 11 different Pacific islands. There is quite a bit of variation, but the pattern is clear: the more modernized, the higher the diabetes rate. In several cases, the table has placed two values side-by-side: one value for rural inhabitants of an island, and another for urban inhabitants of the same island. In every case, the prevalence of diabetes is higher in the urban group. In some cases, the difference is as large as four-fold.

The lowest value goes to the New Caledonians of Touho, who are also considered the least modernized on the table (although even their diet is not completely traditional). Men have an age-standardized diabetes prevalence of 1.8%, women 1.4%. At the other extreme are the Micronesians of Nauru, affluent due to phosphate resources, who have a prevalence of 33.4% for men and 32.1% for women. They subsist mostly on imported food and are extremely obese.

The same patterns can be seen in Africa, the Arctic and probably everywhere that has adopted processed Western foods. White rice alone (compared with the combination of wheat flour and sugar) does not seem to have this effect.

The data in this post are from the book Migration and Health in a Small Society: the Case of Tokelau.

The Tokelau Island Migrant Study: Background and Overview
The Tokelau Island Migrant Study: Dental Health
The Tokelau Island Migrant Study: Cholesterol and Cardiovascular Health
The Tokelau Island Migrant Study: Weight Gain

Asthma

The Tokelau Island Migrant Study: Asthma

Asthma may be another "disease of civilization", uncommon in non-industrial cultures. Between 1980 and 2001, its prevalence more than doubled in American children 17 years and younger. The trend is showing no sign of slowing down (CDC NHANES surveys).



The age-standardized asthma prevalence in Tokelauan migrants to New Zealand age 15 and older, was 2 - 6 times higher than in non-migrants from 1976 to 1982, depending on gender and year. The highest prevalence was in New Zealand migrant women in 1976, at 6.8%. The lowest was in Tokelauan men in 1976 at 1.1%.

A skeptic might suggest it's because these adults grew up around certain types of pollen or other antigens, and were exposed to new ones later in life. However, even migrant children in the 0-4 age group, who were most likely born in NZ, had more asthma than on Tokelau.

What could contribute to the increased asthma prevalence upon modernization? I'm not particularly knowledgeable about the mechanisms of asthma, but it seems likely to involve a chronic over-activation of the immune system ("inflammation").

The Tokelau Island Migrant Study: Background and Overview
The Tokelau Island Migrant Study: Dental Health
The Tokelau Island Migrant Study: Cholesterol and Cardiovascular Health
The Tokelau Island Migrant Study: Weight Gain
The Tokelau Island Migrant Study: Diabetes

Gout

The Tokelau Island Migrant Study: Gout

Gout is a disorder in which uric acid crystals form in the joints, causing intense pain. The body forms uric acid as a by-product of purine metabolism. Purines are a building block of DNA, among other things. Uric acid is normally excreted into the urine, hence the name.

On Tokelau between 1971 and 1982, gout prevalence fell slightly. In migrants to New Zealand, gout prevalence began at the same level as on Tokelau but increased rapidly over the same time period. Here are the prevalence data for men, from Migration and Health in a Small Society: the Case of Tokelau (I don't have data for women):

This paper found that the age-standardized risk of developing gout was 9 times higher in New Zealand than on Tokelau for men, and 2.7 times higher for women.

The Tokelau Island Migrant Study: Background and Overview
The Tokelau Island Migrant Study: Dental Health
The Tokelau Island Migrant Study: Cholesterol and Cardiovascular Health
The Tokelau Island Migrant Study: Weight Gain
The Tokelau Island Migrant Study: Diabetes
The Tokelau Island Migrant Study: Asthma

The Final Word

The Tokelau Island Migrant Study: The Final Word

Over the course of the last month, I've outlined some of the major findings of the Tokelau Island Migrant study. It's one of the most comprehensive studies I've found of a traditional culture transitioning to a modern diet and lifestyle. It traces the health of the inhabitants of the Pacific island Tokelau over time, as well as the health of Tokelauan migrants to New Zealand. 

Unfortunately, the study began after the introduction of modern foods. We will never know for sure what Tokelauan health was like when their diet was completely traditional. To get some idea, we have to look at other traditional Pacific islanders such as the Kitavans. 

What we can say is that an increase in the consumption of modern foods on Tokelau, chiefly white wheat flour and refined sugar, correlated with an increase in several non-communicable disorders, including overweight, diabetes and severe tooth decay. Further modernization as Tokelauans migrated to New Zealand corresponded with an increase in nearly every disorder measured, including heart disease, weight gain, diabetes, asthma and gout. These are all "diseases of civilization", which are not observed in hunter-gatherers and certain non-industrial populations throughout the world. 

One of the most interesting things about Tokelauans is their extreme saturated fat intake, 40- 50% of calories. That's more than any other population I'm aware of. Yet Tokelauans appear to have a low incidence of heart attacks, lower than their New Zealand- dwelling relatives who eat half as much saturated fat. This should not be buried in the scientific literature; it should be common knowledge.

Overall, I believe the Tokelau Island Migrant study (among others) shows us that partially replacing nourishing traditional foods with modern foods such as processed wheat and sugar, is enough to cause a broad range of disorders not seen in hunter-gatherers but typical of modern societies. Changes in lifestyle between Tokelau and New Zealand may have also played a role.The Tokelau Island Migrant Study: Background and Overview
The Tokelau Island Migrant Study: Dental Health
The Tokelau Island Migrant Study: Cholesterol and Cardiovascular Health
The Tokelau Island Migrant Study: Weight Gain
The Tokelau Island Migrant Study: Diabetes
The Tokelau Island Migrant Study: Asthma 
The Tokelau Island Migrant Study: Gout

Stuck at the Starting Gate?

The Diet-Heart Hypothesis: Stuck at the Starting Gate?

The diet-heart hypothesis is the idea that (1) dietary saturated fat, and in some versions, dietary cholesterol, raise blood cholesterol in humans and (2) therefore contribute to the risk of heart attack. 

I'm not going to spend a lot of time on the theory in relation to dietary cholesterol because the evidence that typical dietary amounts cause heart disease in humans is weak.  Here's a graph from the Framingham Heart study (via the book Prevention of Coronary Heart Disease, by Dr. Harumi Okuyama et al.) to drive home the point. Eggs are the main source of cholesterol in the American diet. In this graph, the "low" group ate 0-2 eggs per week, the "medium" group ate 3-7, and the "high" group ate 7-14 eggs per week (click for larger image):The distribution of blood cholesterol levels between the three groups was virtually identical. The study also found no association between egg consumption and heart attack risk. Dietary cholesterol does not have a large impact on serum cholesterol in the long term, perhaps because humans are adapted to eating cholesterol. Most people are able to adjust their own cholesterol metabolism to compensate when the amount in the diet increases. Rabbits don't have that feedback mechanism because their natural diet doesn't include cholesterol, so feeding them dietary cholesterol increases blood cholesterol and causes vascular pathology. 

The first half of the diet-heart hypothesis states that eating saturated fat raises blood cholesterol. This has been accepted without much challenge by diet-health authorities for nearly half a century. In 1957, Dr. Ancel Keys proposed a formula (Lancet 2:1959. 1957) to predict changes in total cholesterol based on the amount of saturated and polyunsaturated fat in the diet. This formula, based primarily on short-term trials from the 1950s, stated that saturated fat is the primary dietary influence on blood cholesterol.

According to Keys' interpretation of the trials, saturated fat raised, and to a lesser extent polyunsaturated fat lowered, blood cholesterol. But there were significant flaws in the data from the very beginning, which were pointed out in this critical 1973 literature review in the American Journal of Clinical Nutrition (free full text).

The main problem is that the controlled trials typically compared saturated fats to omega-6 linoleic acid (LA)-rich vegetable oils, and when serum cholesterol was higher in the saturated fat group, this was most often attributed to the saturated fat raising blood cholesterol rather than the LA lowering it. When a diet high in saturated fat was compared to the basal diet without changing LA, often no significant increase in blood cholesterol was observed. Studies claiming to show a cholesterol-raising effect of saturated fat often introduced it after an induction period rich in LA. Thus, the effect sometimes had more to do with LA lowering blood cholesterol than saturated fat raising it. This is not at all what I was expecting to find when I began looking through these trials.

Reading through the short-term controlled trials, I was surprised by the variability and lack of agreement between them. Some of this was probably due to a lack of control over variables and non-optimal study design. But if saturated fat has a dominant effect on serum cholesterol in the short term, it should be readily and consistently demonstrable.  

The long-term data are not kind to the diet-heart hypothesis. Reducing saturated fat while greatly increasing LA certainly does lower blood cholesterol substantially. This was the finding in the well-controlled Minnesota Coronary Survey trial, for example (14% reduction). But in other cases where LA intake changed less, such as MRFIT, the Women's Health Initiative Diet Modification trial and the Lyon Diet-Heart trial, reducing saturated fat intake had little or no effect on total cholesterol or LDL (0-3% reduction).  The small changes that did occur could have been due to other factors, such as increased fiber and phytosterols, since these were multiple-factor interventions. 

Another blow to the idea that saturated fat raises cholesterol in the long term comes from observational studies. Here's a graph of data from the Health Professionals Follow-up study, which followed 43,757 health professionals for 6 years (via the book Prevention of Coronary Heart Diseaseby Dr. Harumi Okuyama et al.):What this graph shows is that at a relatively constant LA intake, neither saturated fat intake nor the ratio of LA to saturated fat were related to blood cholesterol in freely living subjects. This was true across a wide range of saturated fat intakes (7-15%). 

There's more. If saturated fat were important in determining the amount of blood cholesterol in the long term, you'd expect populations who eat the most saturated fat to have high blood cholesterol levels. But that's not the case. The Masai traditionally get a high proportion of their calories from milk fat, half of which is saturated. In 1964, Dr. George V. Mann published a paper showing that traditional Masai warriors eating practically nothing but very fatty milk, blood and meat had an average cholesterol of 115 mg/dL in the 20-24 year age group. For comparison, he published values for American men in the same age range: 198 mg/dL (J. Atherosclerosis Res. 4:289. 1964). Apparently, eating three times the saturated animal fat and several times the cholesterol of the average American wasn't enough to elevate their blood cholesterol. What does elevate the cholesterol of a Masai man?Junk food. 

Now let's swim over to the island of Tokelau, where the traditional diet includes nearly 50% of calories from saturated fat from coconut. This is the highest saturated fat intake of any population I'm aware of. How's their cholesterol? Men in the age group 20-24 had a concentration of 168 mg/dL in 1976, which was lower than Americans in the same age group despite a four-fold higher saturated fat intake. Tokelauans who migrated to New Zealand, eating half the saturated fat of their island relatives, had a total cholesterol of 191 mg/dL in the same age group and time period, and substantially higher LDL (J. Chron. Dis. 34:45. 1981). Sucrose consumption was 2% on Tokelau and 13% in New Zealand. Saturated fat seems to take a backseat to some other diet/lifestyle factor(s).  Body fatness and excess calorie intake are good candidates, since they influence circulating lipoproteins.

Does dietary saturated fat influence total cholesterol and LDL over the long term?  I don't have the answers, but I do think it's interesting that the evidence is much less consistent than it's made out to be.  It may be that if dietary saturated fat influences total cholesterol or LDL concentration in the long term, the effect is is secondary to other factors.  That being said, it's clear that linoleic acid, in large amount, reduces circulating total cholesterol and LDL.

High-Fat Dairy, Obesity, Metabolic Health and Cardiovascular Disease.

New Review Paper by Yours Truly: High-Fat Dairy, Obesity, Metabolic Health and Cardiovascular Disease

My colleagues Drs. Mario Kratz, Ton Baars, and I just published a paper in the European Journal of Nutrition titled "The Relationship Between High-Fat Dairy Consumption and Obesity, Cardiovascular, and Metabolic Disease".  Mario is a nutrition researcher at the Fred Hutchinson Cancer Research Center here in Seattle, and friend of mine.  He's doing some very interesting research on nutrition and health (with an interest in ancestral diets), and I'm confident that we'll be getting some major insights from his research group in the near future.  Mario specializes in tightly controlled human feeding trials.  Ton is an agricultural scientist at the University of Kassel in Germany, who specializes in the effect of animal husbandry practices (e.g., grass vs. grain feeding) on the nutritional composition of dairy.  None of us have any connection to the dairy industry or any other conflicts of interest.

The paper is organized into three sections:

1. A comprehensive review of the observational studies that have examined the relationship between high-fat dairy and/or dairy fat consumption and obesity, metabolic health, diabetes, and cardiovascular disease.
2. A discussion of the possible mechanisms that could underlie the observational findings.
3. Differences between pasture-fed and conventional dairy, and the potential health implications of these differences.

 We wrote this paper because after reviewing the evidence, we found it to be surprising and fairly contradictory to conventional ideas on nutrition and health.  I wrote the sections on obesity, metabolic health and diabetes, Mario wrote the sections on cardiovascular disease and fatty acids, and Ton wrote the section on husbandry practices and dairy fat composition.  Mario was the lead author and did most of the editing/formatting, submitted the manuscript, etc.  Our paper went through a rigorous peer review process.

Here are our basic findings:

• High-fat dairy consumption is not associated with obesity, in fact, 11 out of 16 studies found that higher dairy fat intake is associated with lower body fat and/or less fat gain over time.  None identified an association between high-fat dairy consumption and fat gain, although some did find an association between low-fat dairy consumption and fat gain.
• High-fat dairy consumption is not associated with poorer metabolic health.  Six of 11 studies found that higher high-fat dairy consumption is associated with better metabolic health, while only one found that it was associated with one marker of poorer metabolic health (and this study used an odd design). 
• The association between high-fat dairy intake and diabetes risk is inconsistent.  Zero of eight studies found that high-fat dairy consumption is associated with diabetes risk, and three found that it was protective.  However, three studies also found that low-fat dairy intake was inversely associated with diabetes risk, compared to no association with high-fat dairy, suggesting by inference that the fat content of the dairy could be harmful.  These studies all adjusted for body fatness.  Since body fatness is a key risk factor for diabetes, and dairy fat intake is inversely associated with body fatness, this is obviously a major confound.  We discussed this and other potential confounds in the paper.
• The evidence on cardiovascular disease is inconsistent, with a number of studies suggesting a protective association, a few suggesting a harmful one, and several suggesting no association.
• Dairy fat is a complex substance.  There are major differences in the fatty acid composition of dairy from pasture-raised vs. conventionally raised cows, and many of these fatty acids are bioactive and could influence human health.
• We also discuss the limitations of observational studies in some detail, and many other issues that I won't touch on here.

What This Paper Means 

This is the first comprehensive review of studies on the association between high-fat dairy intake and obesity, metabolic, and cardiovascular health.  Typical dietary advice includes the recommendation to eat low-fat or skim dairy products.  This is based on the hypothesis that avoiding the (mostly saturated) fat in dairy will reduce the risk of obesity, metabolic problems, and cardiovascular disease.  This idea is logical, but not every idea that is logical is correct when tested scientifically, particularly when it pertains to a complex natural food.  We asked the question "what does the evidence say about this hypothesis?"

The research to date suggests that high-fat dairy overall does not have a negative impact on obesity risk, metabolic problems, diabetes risk, or cardiovascular disease.  In fact, these studies offer fairly strong support to the hypothesis that high-fat dairy may protect against obesity.  However, there was variability between studies and this may be explained by factors such as a) differences in the quality of dairy products between countries/regions, b) the form in which dairy is consumed (e.g., traditional cheeses vs. ice cream and pizza), and c) other confounding factors discussed in the paper. 

Please keep in mind that these studies are observational and therefore can not establish cause and effect. They're best viewed as a springboard for future research.

What This Paper Doesn't Mean

I want to be very clear about this.  This paper does not mean that adding butter to all your food will make you lose fat or become healthier.  In fact, if you do that you will most likely gain fat and become less healthy.  Say what??  The studies we reviewed examined the role of high-fat dairy in the context of normal varied diet patterns.  They did not compare people eating normally to people who put extra butter on everything, which is an excellent way to increase your calorie intake.  Essentially they compared people eating high-fat dairy to people eating other types of fats as part of a mixed diet.  The difference is subtle but critical to understand: addition vs. replacement. 

So does this mean that replacing other types of fats with dairy fat (pasture-raised in particular), in the context of a normal varied diet, could lead to less fat gain and perhaps even better health over time?  Perhaps.  That is what the studies suggest overall.  But again, these are observational studies with major limitations, so we'll have to wait for more evidence before we can hang our hats on the idea.  In the meantime, it's clear that typical dietary recommendations to favor low-fat dairy over high-fat dairy are on thin ice.

Cancer and the Immune System

Cancer and the Immune System

My understanding of cancer has changed radically over the past few months. I used to think of it as an inevitable consequence of aging, a stochastic certainty. The human body is made of about 50 trillion cells, many of which replicate their DNA and divide regularly. It's only a matter of time until one of those cells randomly accumulates the wrong set of mutations, and loses the molecular brakes that restrict uncontrolled growth. 

Strictly speaking, the idea is correct. That is how cancer begins. However, there's another check in place that operates outside the cancer cell itself: the immune system. A properly functioning immune system can recognize and destroy cancerous cells before they become dangerous to the organism. In fact, your immune system has probably already controlled or destroyed a number of them in your lifetime. 

I recently read a fascinating account of some preliminary findings from the lab of Dr. Zheng Cui at Wake Forest university. His group took blood samples from 100 people and purified a type of immune cell called the granulocyte. They then evaluated the granulocytes' ability to kill cervical cancer cells in a cell culture dish. They found that it varied dramatically from one individual to another. One person's granulocytes killed 97% of the cancer cells in 24 hours, while another person's killed 2%. 

They found some important trends. Granulocytes from people over 50 years old had a reduced ability to kill cancer cells, as did granulocytes from people with cancer. This raises the possibility that cancer is not simply the result of getting too old, but a very specific weakening of the immune system.

The most important finding, however, was that the granulocytes' kung-fu grip declined dramatically during the winter months. Here's Dr. Cui:

Nobody seems to have any cancer-killing ability during the
winter months from November to April.

Hmm, I wonder why that could be?? Vitamin D anyone??

Cancer Among the Inuit

Cancer Among the Inuit

I remember coming across a table in the book Eat, Drink and Be Healthy (by Dr. Walter Willett) a few years back. Included were data taken from Dr. Ancel Keys' "Seven Countries Study". It showed the cancer rates for three industrialized nations: the US, Greece and Japan. Although specific cancers differed, the overall rate was remarkably similar for all three: about 90 cancers per 100,000 people per year. Life expectancy was also similar, with Greece leading the pack by 4 years (the data are from the 60s). 

The conclusion I drew at the time was that lifestyle did not affect the likelihood of developing cancer. It was easy to see from the same table that heart disease was largely preventable, since the US had a rate of 189 per 100,000 per year, compared to Japan's 34. Especially since I also knew that Japanese-Americans who eat an American diet get heart disease just like European-Americans. 

I fell prey to the same logic that is so pervasive today: the idea that you will eventually die of cancer if no other disease gets you first. It's easy to believe, since the epidemiology seems to tell us that lifestyle doesn't affect overall cancer rates very much. There's only one little glitch... those epidemiological studies compare the sick to the sicker. 

Here's the critical fact that modern medicine seems to have forgotten: hunter-gatherers and numerous non-industrial populations throughout the world have unusually low cancer rates. This idea was widely accepted in the 19th century and the early 20th, but has somehow managed to fade into obscurity.  Allow me to explain. 

I recently read Cancer, Disease of Civilization by Vilhjalmur Stefansson (thanks Peter). Stefansson was an anthropologist and arctic explorer who participated in the search for cancer among the Canadian and Alaskan Inuit. Traditionally, most Inuit groups were mostly carnivorous, eating a diet of raw and cooked meat and fish almost exclusively. Their calories came primarily from fat. They alternated between seasons of low and high physical activity, typically enjoyed an abundant food supply yet also periodically faced famines. 

Field physicians in the arctic noted that the Inuit were a remarkably healthy people. While they suffered from a tragic susceptibility to European communicable diseases, they did not develop the chronic diseases we now view as part of being human: tooth decay, overweight, heart attacks, appendicitis, constipation, diabetes and cancer. When word reached American and European physicians that the Inuit did not develop cancer, a number of them decided to mount an active search for it. This search began in the 1850s and tapered off in the 1920s, as traditionally-living Inuit became difficult to find. 

One of these physicians was captain George B. Leavitt. He actively searched for cancer among the traditionally-living Inuit from 1885 to 1907. Along with his staff, he claims to have performed tens of thousands of examinations. He did not find a single case of cancer. At the same time, he was regularly diagnosing cancers among the crews of whaling ships and other Westernized populations. It's important to note two relevant facts about Inuit culture: first, their habit of going shirtless indoors. This would make visual inspection for external cancers very easy. Second, the Inuit generally had great faith in Western doctors and would consult them even for minor problems. Therefore, doctors in the arctic had ample opportunity to inspect them for cancer. 

A study was published in 1934 by F.S. Fellows in the US Treasury's Public Health Reports entitled "Mortality in the Native Races of the Territory of Alaska, With Special Reference to Tuberculosis". It contained a table of cancer mortality deaths for several Alaskan regions, all of them Westernized to some degree. However, some were more Westernized than others. In descending order of Westernization, the percent of deaths from cancer were as follows:


Keep in mind that all four of the Inuit populations in this table were somewhat Westernized. It's clear that cancer incidence tracks well with Westernization, although other factors could be involved in producing this result (such as poorer diagnosis in less Westernized regions). By "Westernization", what I mean mostly is the adoption of European food habits, including wheat flour, sugar, canned goods and vegetable oil. Later, most groups also adopted Western-style houses, which incidentally were not at all suited to their harsh climate. 

In the next post, I'll address the classic counter-argument that hunter-gatherers were free of cancer because they didn't live long enough to develop it.

Mortality and Lifespan of the Inuit

Mortality and Lifespan of the Inuit

One of the classic counter-arguments that's used to discredit accounts of healthy hunter-gatherers is the fallacy that they were short-lived, and thus did not have time to develop diseases of old age like cancer. While the life expectancy of hunter-gatherers was not as high as ours today, most groups had a significant number of elderly individuals, who sometimes lived to 80 years and beyond. Mortality came mostly from accidents, warfare and infectious disease rather than chronic disease. 

I found a a mortality table from the records of a Russian mission in Alaska (compiled by Veniaminov, taken from Cancer, Disease of Civilization), which recorded the ages of death of a traditionally-living Inuit population during the years 1822 to 1836. Here's a plot of the raw data:

Here's the data re-plotted in another way. I changed the "bin size" of the bars to 10 year spans each (rather than the bins above, which vary from 3 to 20 years). This allows us to get a better picture of the number of deaths over time. I took some liberties with the data to do this, breaking up a large bin equally into two smaller bins. I also left out the infant mortality data, which are interesting but not relevant to this post: 

Excluding infant mortality, about 25% of their population lived past 60. Based on these data, the approximate life expectancy (excluding infant mortality) of this Inuit population was 43.5 years. It's possible that life expectancy would have been higher before contact with the Russians, since they introduced a number of nasty diseases to which the Inuit were not resistant. Keep in mind that the Westerners who were developing cancer alongside them probably had a similar life expectancy at the time. Here's the data plotted in yet another way, showing the number of individuals surviving at each age, out of the total deaths recorded:

It's remarkably linear. Here's the percent chance of death at each age:


In the next post, I'll briefly summarize cancer data from several traditionally-living cultures other than the Inuit.