Clarifications About Carbohydrate and Insulin

My statements about carbohydrate and insulin in the previous post seem to have kicked up some dust!  Some people are even suggesting I've gone low-fat!  I'm going to take this opportunity to be more specific about my positions.

I do not think that post-meal insulin spikes contribute to obesity, and they may even oppose it.  I'm not aware of anyone who researches metabolism for a living who thinks post-meal insulin spikes contribute to obesity, and after having looked into it, I understand why.  It's not a controversial issue in my field as far as I can tell. Elevated fasting insulin is a separate issue-- that's a marker of insulin resistance.  It's important not to confuse the two.  Does insulin resistance contribute to obesity?  I don't know, but it's hypothetically possible since insulin acts like leptin's kid brother in some ways.  As far as I can tell, starch per se and post-meal insulin spikes do not lead to insulin resistance.
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Eating Down the Food Chain

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 climate. What the new study shows is that the same large animals survived for another 5,000 years in Tasmania... until humans arrived there from the mainland. Then they promptly went extinct. That time period didn't correspond to a major climate change, so it's hard to explain it away.

It's a harsh reality that our big brains and remarkable adaptability give us the power to be exceptionally destructive to the environment. We're good at finding the most productive niches available, and exploiting them until they implode. Jared Diamond wrote an excellent book on the subject called Collapse, which details how nearly every major civilization collapse throughout history was caused at least in part by environmental damage. It's been a hallmark of human history since the beginning.

I don't think it will take much to convince you that the trend has accelerated in modern times. Ocean life, our major source of nutrient-rich wild food, has already been severely depleted. The current extinction rate is estimated to be over 1,000 times the baseline, pre-modern level, and rising.

Humans have always been top-level predators. We kill and eat nutrient-dense prey that is often much larger than we are. But today, the extinction of such walking meat lockers has caused us to eat down the food chain. We're turning to jellyfish and sea cucumbers and... gasp... lobsters!

While it's true that we've probably always eaten things like shellfish and insects, I find it disturbing that we've depleted the oceans to the point where we can no longer sustainably eat formerly abundant carnivorous fish like tuna. We need to make a concerted effort to preserve these species because extinction is permanent.

I don't want to live in a future where the only thing on the menu is bacteria patties, the other other other other white meat.

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 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!

Book Review: "The Human Diet: Its Origins and Evolution"

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.

Grains and Human Evolution

You've heard me say that I believe grains aren't an ideal food for humans. Part of the reason rests on the assertion that we have not been eating grains for long enough to have adapted to them. In this post, I'll go over what I know about the human diet before and after agriculture, and the timeline of our shift to a grain-based diet. I'm not an archaeologist so I won't claim that all these numbers are exact, but I think they are close enough to make my point.

As hunter-gatherers, we ate some combination of the following: land mammals (including organs, fat and marrow), cooked tubers, seafood (fish, mammals, shellfish, seaweed), eggs, nuts, fruit, honey, "vegetables" (stems, leaves, etc.), mushrooms, assorted land animals, birds and insects. The proportion of each food varied widely between groups and even seasons. This is pretty much what we've been living on since we evolved as a species, and even before, for a total of 1.5 million years or so (this number is controversial but is supported by multiple lines of evidence). There are minor exceptions, including the use of wild grains in a few areas, but for the most part, that's it.

The first evidence of a calorically important domesticated crop I'm aware of was about 11,500 years ago in the fertile crescent. They were cultivating an early ancestor of wheat called emmer. Other grains popped up independently in what is now China (rice; ~10,000 years ago), and central America (corn; ~9,000 years ago). That's why people say humans have been eating grains for about 10,000 years.

The story is more complicated than the dates suggest, however. Although wheat had its origin 11,500 years ago, it didn't become widespread in Western Europe for another 4,500 years. So if you're of European descent, your ancestors have been eating grains for roughly 7,000 years. Corn was domesticated 9,000 years ago, but according to the carbon ratios of human teeth, it didn't become a major source of calories until about 1,200 years ago! Many American groups did not adopt a grain-based diet until 100-300 years ago, and in a few cases they still have not. If you are of African descent, your ancestors have been eating grains for 9,000 to 0 years, depending on your heritage. The change to grains was accompanied by a marked decrease in dental health that shows up clearly in the archaeological record.

Practically every plant food contains some kind of toxin, but grains produce a number of nasty ones that humans are not well adapted to. Grains contain a large amount of phytic acid for example, which strongly inhibits the absorption of a number of important minerals. Tubers, which were our main carbohydrate source for about 1.5 million years before agriculture, contain less of it. This may have been a major reason why stature decreased when humans adopted grain-based agriculture. There are a number of toxins that occur in grains but not in tubers, such as certain heat-resistant lectins.

Non-industrial cultures often treated their seeds, including grains, differently than we do today. They used soaking, sprouting and long fermentation to decrease the amount of toxins found in grains, making them more nutritious and digestible. Most grain staples are not treated in this way today, and so we bear the brunt of their toxins even more than our ancestors did.

From an evolutionary standpoint, even 11,500 years is the blink of an eye. Add to that the fact that many people descend from groups that have been eating grains for far less time than that, and you begin to see the problem. There is no doubt that we have begun adapting genetically to grains. All you have to do to understand this is look back at the archaeological record, to see the severe selective pressure (read: disease) that grains placed on its early adopters. But the question is, have we had time to adapt sufficiently to make it a healthy food? I would argue the answer is no.

There are a few genetic adaptations I'm aware of that might pertain to grains: the duplication of the salivary amylase gene, and polymorphisms in the angiotensin-converting enzyme (ACE) and apolipoprotein B genes. Some groups duplicated a gene that secretes the enzyme amylase into the saliva, increasing its production. Amylase breaks down starch, indicating a possible increase in its consumption. The problem is that we were getting starch from tubers before we got it from grains, so it doesn't really argue for either side in my opinion. The ACE and apolipoprotein B genes may be more pertinent, because they relate to blood pressure and LDL cholesterol. Blood pressure and blood cholesterol are both factors that respond well to low-carbohydrate (and thus low-grain) diets, suggesting that the polymorphisms may be a protective adaptation against the cardiovascular effects of grains.

The fact that up to 1% of people of European descent may have full-blown celiac disease attests to the fact that 7,000 years have not been enough time to fully adapt to wheat on a population level. Add to that the fact that nearly half of genetic Europeans carry genes that are associated with celiac, and you can see that we haven't been weeded out thoroughly enough to tolerate wheat, the oldest grain!

Based on my reading, discussions and observations, I believe that rice is the least problematic grain, wheat is the worst, and everything else is somewhere in between. If you want to eat grains, it's best to soak, sprout or ferment them. This activates enzymes that break down most of the toxins. You can soak rice, barley and other grains overnight before cooking them. Sourdough bread is better than normal white bread. Unfermented, unsprouted whole wheat bread may actually be the worst of all.