diet
gluten
hyperphagia
leptin
overweight
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 that our increased food intake, or hyperphagia, is the result of metabolic disturbances, rather than the cause of them.Humans, like all animals, have a sophisticated system of hormones and brain regions whose function is to maintain a proper energy balance. Part of the system's job is to keep fat mass at an appropriate level. With a properly functioning system, feedback loops inhibit hunger once fat mass has reached a certain level, and also increase resting metabolic rate to burn excess calories. If the system is working properly, it's very difficult to gain weight. There have been a number of overfeeding studies in which subjects have consumed huge amounts of excess calories. Some people gain weight, many don't.The fact that fat mass is hormonally regulated can be easily seen in other mammals. When was the last time you saw a fat squirrel in the springtime? When was the last time you saw a thin squirrel in the fall? These events are regulated by hormones. A squirrel in captivity will put on weight in the fall, even if its daily food intake is not changed.A key hormone in this process is leptin. Leptin levels are proportional to fat mass, and serve to inhibit hunger and eating behaviors. Under normal conditions, the more fat tissue a person has, the more leptin they will produce, and the less they will eat until the fat mass has reached the body's preferred 'set-point'. The problem is that overweight Westerners are almost invariably leptin-resistant, meaning their body doesn't respond to the signal to stop eating!Leptin resistance leads to hyperphagia, overweight and the metabolic syndrome (a common cluster of symptoms that implies profound metabolic disturbance). It typically precedes insulin resistance during the downward slide towards metabolic syndrome.I suspect that wheat, sugar and perhaps other processed foods cause hyperphagia. I believe hyperphagia is at least partially secondary to a disturbed metabolism. There's something about industrial foods that reached a critical mass in the mid-70s. The shift in diet sent us into a tailspin of excessive eating and unprecedented weight gain.
diet
fats
overweight
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 "added fats" with "total fat". While total fat intake has remained stable over this time period, added fats have increased by 59%. The increase is almost exclusively due to industrially processed seed oils (butter and lard have decreased). Total fat has remained the same because we now eat low-fat cuts of meat and low-fat dairy products to make up for it! Another problem with the article is it only shows percent changes in consumption of different foods, rather than absolute amounts. This obscures some really meaningful information. For example, grain consumption is up a whopping 42%. That is the largest single food group change if you exclude the misinterpreted fat data. Corn is up 188%, rice 170%, wheat 21%. But in absolute amounts, the increase in wheat consumption is larger than corn or rice! That's because baseline wheat consumption dwarfed corn and rice. We don't get that information from the data presented in the article, due to the format. So now that I've deconstructed the data, let's see what the three biggest changes in the American diet from 1970 to 2006 actually are:- We're eating more grains, especially white wheat flour
- We're eating more added sweeteners, especially high-fructose corn syrup
- Animal fats from milk and meat have been replaced by processed seed oils
Wheat + sugar + processed vegetable oil = fat and unhealthy. Sounds familiar, doesn't it?
archaeology
paleolithic diet
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 Mediterranean region. Paleolithic skeletons indicated a life expectancy of 35.4 years for men and 30.0 years for women, which includes a high rate of infant mortality. This is consistent with data from the Inuit that I posted a while back (life expectancy excluding infant mortality = 43.5 years). With modest fluctuations, the life expectancy of humans in this Mediterranean region remained similar from paleolithic times until the last century. I suspect the paleolithic people died most often from warfare, accidents and infectious disease, while the neolithic people died mostly from chronic disease, and infectious diseases that evolved along with the domestication of animals (zoonotic diseases). But I'm just speculating based on what I know about modern populations, so you can take that at face value.The most interesting part of the table is actually not the life expectancy data. It also contains numbers for average stature and pelvic inlet depth. These are both markers of nutritional status during development. Pelvic inlet depth is a measure of the size of the pelvic canal through which a baby would pass during birth. It can be measured in men and women, but obviously its implications for birth only apply to women. As you can see in the table, stature and pelvic inlet depth declined quite a bit with the adoption of agriculture, and still have not reached paleolithic levels to this day. The idea that a grain-based diet interferes with normal skeletal development isn't new. It's well-accepted in the field of archaeology that the adoption of grains coincided with a shortening of stature, thinner bones and crooked, cavity-ridden teeth. This fact is so well accepted that these sorts of skeletal changes are sometimes used as evidence that grains were adopted in a particular region historically. Weston Price saw similar changes in the populations he studied, as they transitioned from traditional diets to processed-food diets rich in white wheat flour, sweets and other processed foods. The change in pelvic inlet depth is also very telling. Modern childbirth is so difficult, it makes you wonder why our bodies have evolved to make it so drawn-out and lethal. Without the aid of modern medicine, many of the women who now get C-sections and other birth interventions would not make it. My feeling is that we didn't evolve to make childbirth so lethal. It's more difficult in modern times, at least partially because we have a narrower pelvic inlet than our ancestors. Another thing Weston Price commented on was the relative ease of childbirth in many of the traditional societies he visited. Here's an exerpt from Nutrition and Physical Degeneration:A similar impressive comment was made to me by Dr. Romig, the superintendent of the government hospital for Eskimos and Indians at Anchorage, Alaska. He stated that in his thirty-six years among the Eskimos, he had never been able to arrive in time to see a normal birth by a primitive Eskimo woman. But conditions have changed materially with the new generation of Eskimo girls, born after their parents began to use foods of modern civilization. Many of them are carried to his hospital after they had been in labor for several days. One Eskimo woman who had married twice, her last husband being a white man, reported to Dr. Romig and myself that she had given birth to twenty-six children and that several of them had been born during the night and that she had not bothered to waken her husband, but had introduced him to the new baby in the morning.
Now that's what I call fertility!
real food
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...
diet
fats
native 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.
archaeology
book review
diet
I recently read this book after discovering it on another health site. It's a compilation of chapters written by several researchers in the fields of comparative biology, paleontology, archaeology and zoology. It's sometimes used as a textbook.
I've learned some interesting things, but overall it was pretty disappointing. The format is disjointed, with no logical flow between chapters. I also would not call it comprehensive, which is one of the things I look for in a textbook. Here are some of the interesting points: - Humans in industrial societies are the only mammals to commonly develop hypertension, and are the only free-living primates to become overweight.
- The adoption of grains as a primary source of calories correlated with a major decrease in stature, decrease in oral health, decrease in bone density, and other problems. This is true for wheat, rice, corn and other grains.
- Cranial capacity has also declined 11% since the late paleolithic, correlating with a decrease in the consumption of animal foods and an increase in grains.
- According to carbon isotope ratios of teeth, corn did not play a major role in the diet of native Americans until 800 AD. Over 15% of the teeth of post-corn South American cultures showed tooth decay, compared with less than 5% for pre-corn cultures (many of which were already agricultural, just not eating corn).
- Childhood mortality seems to be similar among hunter-gatherers and non-industrial agriculturists and pastoralists.
- Women may have played a key role in food procurement through foraging. This is illustrated by a group of modern hunter-gatherers called the Hadza. While men most often hunt, which supplies important nutrients intermittently, women provide a steady stream of calories by foraging for tubers.
- We have probably been eating starchy tubers for between 1.5 and 2 million years, which precedes our species. Around that time, digging tools, (controversial) evidence of controlled fire and changes in digestive anatomy all point to use of tubers and cooked food in general. Tubers make sense because they are a source of calories that is much more easily exploited than wild grains in most places.
- Our trajectory as a species has been to consume a diet with more calories per unit fiber. As compared to chimps, who eat leaves and fruit all day and thus eat a lot of fiber to get enough calories, our species and its recent ancestors ate a diet much lower in fiber.
- Homo sapiens has always eaten meat.
The downside is that some chapters have a distinct low-fat slant. One chapter attempted to determine the optimal diet for humans by comparing ours to the diets of wild chimps and other primates. Of course, we eat more fat than a chimp, but I don't think that gets us anywhere. Especially since one of our closest relatives, the neanderthal, was practically a carnivore.
They consider the diet composition of modern hunter-gatherers that eat low-fat diets, but don't include data on others with high-fat diets like the Inuit.
There's some good information in the book, if you're willing to dig through a lot of esoteric data on the isotope ratios of extinct hominids and that sort of thing.
cancer
Melanoma is the most deadly type of skin cancer, accounting for most skin cancer deaths in the US. As Ross pointed out in the comments section of the last post, there is an association between severe sunburn at a young age and later development of melanoma. Darker-skinned people are also more resistant to melanoma. The association isn't complete, however, since melanoma sometimes occurs on the soles of the feet and even in the intestine. This may be due to the fact that there are several types of melanoma, potentially with different causes.
Another thing that associates with melanoma is the use of sunscreen above a latitude of 40 degrees from the equator. In the Northern hemisphere, 40 degrees draws a line between New York city and Beijing. A recent meta-analysis found consistently that sunscreen users above 40 degrees are at a higher risk of melanoma than people who don't use sunscreen, even when differences in skin color are taken into account. Wearing sunscreen decreased melanoma risk in studies closer to the equator. It sounds confusing, but it makes sense once you know a little bit more about UV rays, sunscreen and the biology of melanoma.
The UV light that reaches the Earth's surface is composed of UVA (longer) and UVB (shorter) wavelengths. UVB causes sunburn, while they both cause tanning. Sunscreen blocks UVB, preventing burns, but most brands only weakly block UVA. Sunscreen allows a person to spend more time in the sun than they would otherwise, and attenuates tanning. Tanning is a protective response (among several) by the skin that protects it against both UVA and UVB. Burning is a protective response that tells you to get out of the sun. The result of diminishing both is that sunblock tends to increase a person's exposure to UVA rays.
It turns out that UVA rays are more closely associated with melanoma than UVB rays, and typical sunscreen fails to prevent melanoma in laboratory animals. It's also worth mentioning that sunscreen does prevent more common (and less lethal) types of skin cancer.
Modern tanning beds produce a lot of UVA and not much UVB, in an attempt to deliver the maximum tan without causing a burn. Putting on sunscreen essentially does the same thing: gives you a large dose of UVA without much UVB.
The authors of the meta-analysis suggest an explanation for the fact that the association changes at 40 degrees of latitude: populations further from the equator tend to have lighter skin. Melanin blocks UVA very effectively, and the pre-tan melanin of someone with olive skin is enough to block most of the UVA that sunscreen lets through. The fair-skinned among us don't have that luxury, so our melanocytes get bombarded by UVA, leading to melanoma. This may explain the incredible rise in melanoma incidence in the US in the last 35 years, as people have also increased the use of sunscreen. It may also have to do with tanning beds, since melanoma incidence has risen particularly in women.
In my opinion, the best way to treat your skin is to tan gradually, without burning. Use clothing and a wide-brimmed hat if you think you'll be in the sun past your burn threshold. If you want to use sunscreen, make sure it blocks UVA effectively. Don't rely on the manufacturer's word; look at the ingredients list. It should contain at least one of the following: titanium dioxide, zinc oxide, avobenzone (Parsol 1789), Mexoryl SX (Tinosorb). It's best if it's also paraben-free.
Fortunately, as an external cancer, melanoma is easy to diagnose. If caught early, it can be removed without any trouble. If caught a bit later, surgeons may have to remove lymph nodes, which makes your face look like John McCain's. Later than that and you're probably a goner. If you have any questions about a growth, especially one with irregular borders that's getting larger, ask your doctor about it immediately!
