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Menampilkan postingan dari Agustus, 2008

Water for the Pima

A few months ago, I published a post about the Pima Indians (Akimel O'odham) of Arizona. The Pima are one of the most heart-wrenching examples of the disease of civilization afflicting a society after a nutrition transition. Traditionally a healthy agricultural people, they now have some of the highest rates of obesity and diabetes in the world.

The trouble all started when their irrigation waters were diverted upstream in the late 19th century. Their traditional diet of corn, beans, squash, fish, game meats and gathered plant foods became impossible. They became dependent on government food programs, which provided them with white flour, sugar, lard and canned goods. Now they are the subjects of scientific research because of their staggering health problems.

I'm happy to report that after more than 30 years of activism, lawsuits and negotiation, the Pima and neighboring tribes have reached an agreement with the federal government that will restore a portion of their …

Conflict of Interest

The U.S. National Cholesterol Education Program (NCEP) is a government organization that educates physicians and the general public about the "dangers" of elevated cholesterol. They have a panel that creates official guidelines for the reduction of cardiovascular disease risk. They contain target cholesterol levels, and the usual recommendations to eat less saturated fat and cholesterol, and lose weight.

They recommend keeping LDL below 100 mg/dL, which would place tens of millions of Americans on statins.

I was reading Dr. John Briffa's blog today and he linked to a government web page disclosing NCEP panel members' conflicts of interest. It's fairly common in academic circles to require conflict of interest statements, so a skeptical audience can decide whether or not they think someone is biased. The 9-member NECP panel was happy to indulge us:
Dr. Grundy has received honoraria from Merck, Pfizer, Sankyo, Bayer, Merck/Schering-Plough, Kos, Abbott, Bristol-Mye…

Eating Down the Food Chain

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Europe once teemed with large mammals, including species of elephant, lion, tiger, bear, moose and bison.

America was also home to a number of huge and unusual animals: mammoths, dire wolves, lions, giant sloths and others.

The same goes for Australia, where giant kangaroos, huge wombats and marsupial 'lions' once roamed.

What do these extinctions have in common? They all occurred around when humans arrived. The idea that humans caused them is hotly debated, because they also sometimes coincided with climactic and vegetation changes. However, I believe the fact that these extinctions occurred on several different continents about when humans arrived points to an anthropogenic explanation.

A recent archaeological study from the island of Tasmania off the coast of Australia supports the idea that humans were behind the Australian extinctions. Many large animals went extinct around the time when humans arrived in Australia, but that time also coincided with a change in climat…

Saharan Hunter-Gatherers Unearthed

The media recently covered an archaeological discovery in Niger that caught my attention. In the middle of the Sahara desert, researchers found a hunter-gatherer burial site containing over 200 graves ranging from about 10,000 to 4,500 years old. During this period, the region was lush and productive.

There were two groups: the Kiffian, who were powerful hunters and fishermen, and the Tenerian, who were smaller pastoralists (herders) and fishermen.

Individuals at the Kiffian sites averaged over 6 feet tall, with some reaching 6' 8". They were powerfully muscled, and found with the remains of elephants, giraffes, pythons, giant perch and other large game.

Not that you have to be Conan the Barbarian to kill an elephant. Forest pygmies traditionally hunt elephants, and there's a picutre in Nutrition and Physical Degeneration to prove it. They use stealth, agility and an intimate knowledge of their prey to make up for their small size and primitive weapons.

Both the Kiff…

Fit at 70

In my professional life, I study neurodegenerative disease, the mechanisms of aging, and what the two have in common. I was reading through a textbook on aging a few months ago, and I came across an interesting series of graphs.

The first graph showed the average cardiorespiratory endurance of Americans at different ages. It peaks around 30 and goes downhill from there. But the author of this chapter was very intelligent; he knew that averages sometimes conceal meaningful information. The second graph showed two lines: one representing a man who was sedentary, and the other representing a man who exercised regularly for his entire life. The data were from real individuals. The endurance of the first man basically tracked the national average as he aged. The endurance of the second man remained relatively stable from early adulthood until the age of 70, after which it declined noticeably.

We aren't taking care of ourselves for nothing, ladies and gentlemen. We're doing …

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 t…

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 ra…

Cardiovascular Risk Factors on Kitava, Part III: Insulin

The Kitava study continues to get more and more interesting in later publications. Dr. Lindeberg and his colleagues continued exploring disease markers in the Kitavans, perhaps because their blood lipid findings were not consistent with what one would expect to find in a modern Western population with a low prevalence of CVD.

In their next study, the researchers examined Kitavans' insulin levels compared to Swedish controls. This paper is short but very sweet. Young Kitavan men and women have a fasting serum insulin level considerably lower than their Swedish counterparts (KM 3.9 IU/mL; SM 5.7; KW 3.5; SW 6.2). Kitavan insulin is relatively stable with age, whereas Swedish insulin increases. In the 60-74 year old group, Kitavans have approximately half the fasting serum insulin of Swedes. One thing to keep in mind is that these are average numbers. There is some overlap between the Kitavan and Swedish numbers, with a few Kitavans above the Swedish mean.

In figure 2, they ad…

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…

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 populat…

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 th…

Letter to the Editor

I wrote a letter to the New York Times about their recent article "The Overflowing American Dinnerplate", which I reviewed here. The letter didn't get accepted, so I will publish it here:


In the article "The Overflowing American Dinner Plate", Bill Marsh cites USDA data showing a 59% increase in fat consumption from 1970 to 2006, coinciding with the doubling of the obesity rate in America. However, according to Centers for Disease Control NHANES nutrition survey data, total fat intake in the US has remained relatively constant since 1971, and has actually decreased as a percentage of calories. The apparent discrepancy disappears when we understand that the USDA data Marsh cites are not comprehensive. They do not include the fat contained in milk and meat, which have been steadily decreasing since 1970.

The change Marsh reported refers primarily to the increasing use of industrially processed vegetable oils such as soybean oil. These have gradually rep…

Rats on Junk Food

If diet composition causes hyperphagia, we should be able to see it in animals. I just came across a great study from the lab of Dr. Neil Stickland that explored this in rats. They took two groups of pregnant rats and fed them two different diets ad libitum, meaning the rats could eat as much as they wanted. Here's what the diets looked like:
The animals were fed two types of diet throughout the study. They were fed either RM3 rodent chow alone ad libitum (SDS Ltd, Betchworth, Surrey, UK) or with a junk food diet, also known as cafeteria diet, which consisted of eight different types of palatable foods, purchased from a British supermarket. The palatable food included biscuits, marshmallows, cheese, jam doughnuts, chocolate chip muffins, butter flapjacks, potato crisps and caramel/chocolate bars.
It's important to note that the junk food-fed rats had access to rat chow as well. Now here's where it gets interesting. Rats with access to junk food in addition to rat chow a…

Hyperphagia

One of the things I didn't mention in the last post is that Americans are eating more calories than ever before. According to Centers for Disease Control NHANES data, in 2000, men ate about 160 more calories per day, and women ate about 340 more than in 1971. That's a change of 7% and 22%, respectively. The extra calories come almost exclusively from refined grains, with the largest single contribution coming from white wheat flour (correction: the largest single contribution comes from corn sweeteners, followed by white wheat flour).

Some people will see those data and decide the increase in calories is the explanation for the expanding American waistline. I don't think that's incorrect, but I do think it misses the point. The relevant question is "why are we eating more calories now than we were in 1971?"

We weren't exactly starving in 1971. And average energy expenditure, if anything, has actually increased. So why are we eating more? I believe t…

Media Misinterpretations

The New York Times just published an article called "The Overflowing American Dinner Plate", in which they describe changes in the American diet since 1970, the period during which the obesity rate doubled. Bill Marsh used USDA estimates of food consumption from 1970 to 2006. Predictably, he focuses on fat consumption, and writes that it has increased by 59% in the same time period.

The problem is, we aren't eating any more fat than we were in 1970. The US Centers for Disease Control NHANES surveys show that total fat consumption has remained the same since 1971, and has decreased as a percentage of calories. I've been playing around with the USDA data for months now, and I can tell you that Marsh misinterpreted it in a bad way. Here are the raw data, for anyone who's interested. They're in easy-to-use Excel spreadsheets. I highly recommend poking around them if you're interested.

The reason Marsh was confused by the USDA data is that he confused &…

Life Expectancy and Growth of Paleolithic vs. Neolithic Humans

If paleolithic people were healthier than us due to their hunter-gatherer lifestyle, why did they have a shorter life expectancy than we do today? I was just reminded by Scott over at Modern Forager about some data on paleolithic (pre-agriculture) vs. neolithic (post-agriculture) life expectancy and growth characteristics. Here's a link to the table, which is derived from an article in the text Paleopathology at the Origins of Agriculture.

The reason the table is so interesting is it allows us to ask the right question. Instead of "why did paleolithic people have a shorter life expectancy than we do today?", we should ask "how did the life expectancy of paleolithic people compare to that of pre-industrial neolithic people?" That's what will allow us to tease the effects of lifestyle apart from the effects of modern medicine.

The data come from age estimates of skeletons from various archaeological sites representing a variety of time periods in the Me…

Hunting

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Like 99.9% of the world's population, I am mostly dependent on agriculture for my food. It's fun to pretend sometimes though. I enjoy foraging for berries, mushrooms and nuts.

Last week, I went crabbing in the San Juan islands. We caught our limit of meaty dungeness crabs every day we put the pots out. If we had been working harder at it (and it was legal), we could easily have caught enough crabs to feed ourselves completely. We cooked them fresh and ate some the same day. We extracted the meat from the rest, and made an amazing crab bisque using a stock made from the shells, and lots of cream.

Here's a "hunting photo". No smiling allowed; I had to look tough...


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. "…