Did We Adapt to Cooked Foods?
Recently, a book was published that seems to contradict a lot of the established raw food theory. The book is called “Catching Fire: How Cooking Made Us Human” by Richard Wrangham, who’s a British primatologist.
A few of my readers have asked me what I think of this book.
So I spent the time reading the 300 page book, initially with some skepticism. I expected another meat-eating scientist trying to rationalize their habits by some unsubstantiated arguments. Instead, I found the book “Catching Fire” to be quite fascinating, bringing light to a lot of controversies that raw-foodists will definitely find interesting.
It also destroys the foundation of many common raw-food myths (that I didn’t believe in anyway), but surprisingly, the basic conclusions of Mr. Wrangham’s research partially support the low-fat, fruit-based diet that I recommend.
Before I go into the details the theory presented in “Catching Fire”, let me review some of the current beliefs common in many books on the raw-food diets (including some of my own):
• Humans are apes. Other apes we know eat a plant-based diet of fruits and vegetables. Chimpanzees and bonobos, which are the types of apes sharing the most DNA with humans, eat a fruit-based diet. Therefore, our natural diet should also be diet of fruits, vegetables, nuts and seeds.
• Before the advent of cooking, humans lived essentially on fruits, vegetables, and perhaps some nuts and seeds and animal products (when they could find them).
• There must have been a “golden period” of time, before cooking, when we lived for much longer than we do today (some claim 120 to 140 years is our natural lifespan). The advent of cooking and processed foods brought the “descent” of man, as far as our health is concerned.
• Humans have not “adapted” to cooked foods. We ate cooked foods for survival purposes, but our bodies are still wearing down from the consumption of these foods. Because cooked food is toxic, the most natural diet would be a diet of 100% raw foods.
• Humans are not carnivores. Meat has no place in the human diet.
• Grains are not our natural foods. We have been eating grains for only a tiny fraction of our history on this planet. Our natural diet, the one we’re the most adapted to, is one of fruits, vegetables, nuts and seeds.
• We should eat a raw food diet because of the enzymes and other essential nutrients that are destroyed in the cooking process.
As you may imagine, the book Catching Fire demolishes most of these claims. The book’s central claim is that cooking played a very key role in our evolution.
“I believe the transformative moment that gave rise to the genus Homo, one of the great transitions in the history of life, stemmed from the control of fire and the advent of cooked meals. Cooking increased the value of our food. It changed our bodies, our brains, our use of time, and our social lives. It made us into consumers of external energy and thereby created an organism with a new relationship to nature, dependent on fuel.”
Now most raw-foodist will definitely deny these claims. After all, cooked food is “poison” and couldn’t possibly have played any role into making us into who we are (at least not in a positive way). Raw-foodists would disagree strongly with the statement that “cooking increases the value of our food.” Raw-foodists believe that cooking only destroys and cannot possibly “improve” anything. However, objectively speaking, Wrangham is correct about something.
The Quest for Calories
All over nature, it seems that the biggest challenge for all animals trying to stay alive is getting enough to eat. Modern humans, on the other hand, spend only a fraction of their day eating.
“Because the amount of time spent chewing is related to body size among primates, we can estimate how long humans would be obliged to spend chewing if we lived on the same kind of raw food that great apes do. Conservatively, it would be 42 percent of the day, or just over five hours of chewing in a twelve-hour period.”
The main thing that cooking does is it increases the overall caloric content of our diet, our at least it enabled us to obtain more calories in less time and with less energy.
it allowed us to eat many rich foods we wouldn’t have been able to eat in nature, such as roots and starches. This was certainly a key element in freeing our ancestors from having to search for foods and chew tough fruits with few calories all day long.
So according to Wrangham, the main appreciable thing that cooking does is simple: it increases the amount of energy we could obtain from our food. By that, of course, he means calories.
“Studies of digestibility show that we use cooked starch very efficiently. The percentage of cooked starch that has been digested by the time it reaches the end of the ileum is at least 95 percent in oats, wheat, potatoes, plantains, bananas, cornflakes, white bread, and the typical European or American diet (a mixture of starchy foods, dairy products, and meat). A few foods have lower digestibility: starch in home-cooked kidney beans and flaked barley has a digestibility of only around 84 percent. Comparable measurements of the digestibility of raw starch are much lower. Digestibility is 71 percent for wheat starch, 51 percent for potatoes, and a measly 48 percent for raw starch in plantains and cooking bananas.”
“We need to know what cooking does. Cooked food does many familiar things. It makes our food safer, creates rich and delicious tastes, and reduces spoilage. Heating can allow us to open, cut, or mash tough foods. But none of these advantages is as important as a little-appreciated aspect: cooking increases the amount of energy our bodies obtain from our food. ”
Of course, one might argue that raw-foods contain more “energy” and nutrients, but the fact is that Wrangham is correct in pointing out that it is easier to get calories from cooked foods than it was, at least for early humans, to get them from wild raw plants.
However, the author is obviously biased in favor of cooking, but I’m sure you have guessed it by now.
“Raw-foodists are dedicated to eating 100 percent of their diets raw, or as close to 100 percent as they can manage. There are only three studies of their body weight, and all find that people who eat raw tend to be thin. The most extensive is the Giessen Raw Food study, conducted by nutritionist Corinna Koebnick and her colleagues in Germany, which used questionnaires to study 513 raw-foodists who ate from 70 percent to 100 percent of their diet raw. They chose to eat raw to be healthy, to prevent illness, to have a long life, or to live naturally. Raw food included not only uncooked vegetables and occasional meat, but also cold-pressed oil and honey, and some items that were lightly heated such as dried fruits, dried meat, and dried fish. Body mass index (BMI), which measures weight in relation to the square of the height, was used as a measure of fatness. As the proportion of food eaten raw rose, BMI fell. The average weight loss when shifting from a cooked to a raw diet was 26.5 pounds (12 kilograms) for women and 21.8 pounds (9.9 kilograms) for men. Among those eating a purely raw diet (31 percent), the body weights of almost a third indicated chronic energy deficiency. The scientists’ conclusion was unambiguous: “a strict raw food diet cannot guarantee an adequate energy supply.” The amount of meat in the Giessen Raw Food diets was not recorded but many raw-foodists eat rather little meat. Could a low meat intake have contributed to their poor energy supply? It is possible. However, among people who eat cooked diets, there is no difference in body weight between vegetarians and meat eaters: when our food is cooked we get as many calories from a vegetarian diet as from a typical cooked diet.”
My comments on this last quote from the book is that it is certainly true that a typical raw food diet is deficient in energy. As I have mentioned every time, vegetables simply do not contain enough calories to sustain life, and raw fats such as avocados are difficult to eat in large quantities to maintain energy levels (especially considering that they are more difficult to digest than cooked starches). The traditional raw-food diet is a weight loss program. It’s not something that can be sustained over the long-term.
Some ridiculous comments are being made because the authors of the study have obviously little knowledge on how one could balance a raw-food diet and make it work. However, the raw-food diet they describe is very typical of what many raw-foodists eat, and the absolute opposite of what I recommend.
Wrangham goes on:
“The energy consequences of forgoing cooked food lead to a consistent reaction, illustrated by journalist Jodi Mardesich when she became a raw-foodist. “I’m hungry. These days, I’m almost always hungry,” she wrote. A typical day began at 7 A.M. when she cut and juiced two ounces of wheat grass. At 8:30 A.M. she had a bowl of “energy soup,” which she describes as a “room-temperature concoction made of sunflower greens, which are the tiny first shoots of a sunflower plant, and rejuvelac, a fermented wheat drink that tastes a lot like bad lemonade.” She added a couple of spoonfuls of blended papaya for interest. Lunch was a salad of sunflower greens, sprouted fenugreek seeds, sprouted broccoli seeds, fermented cabbage, and a loaf made of sprouted sunflower seeds, dehydrated seaweed, and some vegetables.”
“Dinner was more sprouts, avocado chunks, pineapple, red onion, olive oil, raw vinegar, and sea salt. An hour later she was hungry again. In photographs she looks distinctly thin, but she was happy. She described herself as feeling energized, mentally sharper, and more serene. Nevertheless, after six months, during which she lost 18 pounds (8.2 kilograms), she could not resist slipping out for a pizza. Mardesich was not alone in finding a wholly raw diet a challenge. The Giessen Raw Food study found that 82 percent of long-term raw-foodists included some cooked food in their diets.”
The raw diet described above is typical of many people trying to eat raw. Unfortunately, this diet doesn’t work. It obviously is very low in calories (energy) while being high in fat. Unfortunately, that’s the way a lot of raw-foodists try to eat, and it just isn’t sustainable. That’s why I recommend to get sufficient calories from fruit, while keeping your overall diet low in fat.
“Anthropologist Elizabeth Marshall Thomas describes bushman women in Africa’s Kalahari Desert returning to camp at the end of their ordinary long day thoroughly exhausted, because for much of the day they have been squatting and digging and walking, and hefting large loads of food, wood, and children. Even in populations that cook, these natural activity levels are high enough to interfere with reproductive function. If we imagine the lives of our German raw-foodists made more difficult by a daily regime of foraging for food in the wild, their rate of energy expenditure would surely be substantially increased. As a result, many more than 50 percent of the women would be incapable of pregnancy. Then add that the subjects of the Giessen Raw Food study obtained their diets from supermarkets. Their foods were the typical products of modern farming—fruits, seeds, and vegetables all selected to be as delicious as possible. “Delicious” means high energy, because what people like are foods with low levels of indigestible fiber and high levels of soluble carbohydrates, such as sugars. Agricultural improvements have rendered fruits in a supermarket, such as apples, bananas, and strawberries, far higher in quality than their wild ancestors. In our laboratory at Harvard, nutritional biochemist NancyLou Conklin-Brittain finds that carrots contain as much sugar as the average wild fruit eaten by a chimpanzee in Kibale National Park in Uganda. But even carrots are better quality than a typical wild tropical fruit, because they have less fiber and fewer toxic compounds. If the German raw-foodists had been eating wild foods, their energy balance and reproductive performance would have been much lower than found by Koebnick’s team.”
These points are interesting. Even under the best circumstances, where we get hybridized raw foods with lots of calories, most people have trouble getting enough raw food to eat so they’re not hungy all the time. Can you imagine what early humans would have done, with no access to bananas or hybridized high-calorie fruits, supermarket avocados, bottles of oils and packs of nuts? Especially when you consider the fact that early humans were much more active than we are, it makes the “struggle for raw calories” even more obvious.
Wrangham also points out some studies where various groups of people tried to live off wild raw-foods, and in every single case they did not manage to get enough calories to thrive.
“Raw-Foodist thrive only in rich modern environments where they depend on eating exceptionally high-quality foods. Animals do not have the same constraints: they flourish on wild raw foods. The suspicion prompted by the shortcomings of the Evo Diet is correct, and the implication is clear: there is something odd about us. We are not like other animals.”
Are We Just Like Chimpanzees?
The logic of nature is often easy to follow.
Once we realize that we are animals living among other animals, it’s easy to look at nature and try to see where we fit in the grand scheme of things. For example, we might look and try to find other animals similar to us.
Science tells us that humans are apes, related to some degree to chimpanzee by a common, earlier ancestor. We share more DNA with chimpanzees than with any animals on the planet. Looking at these creatures, we can see so many apparent similarities. In fact, I remember reading how many people in England were shocked when they first saw Chimpanzees in a zoo for the first time. Many people were disturbed by the sight of these animals, precisely because they look so similar to us, which was viewed as repulsive for people of that time, who believe that humans were unlike any other animal on the planet.
So raw-foodists look at what apes eat, and although you will find evidences of some meat-eating among them, even scientists admit that they essentially live on fruits and vegetables. Obviously, since we’re apes, our diet should be something along those lines. (not eating dairy, grains, refined foods)
We also know that there are profound differences between chimpanzees and us. How profound?
“Evolutionary benefits of adapting to cooked food are evident from comparing human digestive systems with those of chimpanzees and other apes. The main differences all involve humans having relatively small features. We have small mouths, weak jaws, small teeth, small stomachs, small colons, and small guts overall. In the past, the unusual size of these body parts has mostly been attributed to the evolutionary effects of our eating meat, but the design of the human digestive system is better explained as an adaptation to eating cooked food than it is to eating raw meat.”
“Mick Jagger’s biggest yawn is nothing compared to a chimpanzee’s. Given that the mouth is the entry to the gut, humans have an astonishingly tiny opening for such a large species. All great apes have a prominent snout and a wide grin: chimpanzees can open their mouths twice as far as humans, as they regularly do when eating. If a playful chimpanzee ever kisses you, you will never forget this point. To find a primate with as relatively small an aperture as that of humans, you have to go to a diminutive species, such as a squirrel monkey, weighing less than 1.4 kilograms (3 pounds). In addition to having a small gape, our mouths have a relatively small volume—about the same size as chimpanzee mouths, even though we weigh some 50 percent more than they do. Zoologists often try to capture the essence of our species with such phrases as the naked, bipedal, or big-brained ape. They could equally well call us the small-mouthed ape.”
(…) The difference in mouth size is even more obvious when we take the lips into account. The amount of food a chimpanzee can hold in its mouth far exceeds what humans can do because, in addition to their wide gape and big mouths, chimpanzees have enormous and very muscular lips. When eating juicy foods like fruits or meat, chimpanzees use their lips to hold a large wad of food in the outer part of their mouths and squeeze it hard against their teeth, which they may do repeatedly for many minutes before swallowing. The strong lips are probably an adaptation for eating fruits, because fruit bats have similarly large and muscular lips that they use in the same way to squeeze fruit wads against their teeth. Humans have relatively tiny lips, appropriate for a small amount of food in the mouth at one time.
(…) Human chewing teeth, or molars, also are small—the smallest of any primate species in relation to body size. Continuing farther into the body, our stomachs again are comparatively small. In humans the surface area of the stomach is less than one-third the size expected for a typical mammal of our body weight, and smaller than in 97 percent of other primates. The high caloric density of cooked food suggests that our stomachs can afford to be small. Great apes eat perhaps twice as much by weight per day as we do because their foods are packed with indigestible fiber (around 30 percent by weight, compared to 5 percent to 10 percent or less in human diets). Thanks to the high caloric density of cooked food, we have modest needs that are adequately served by our small stomachs.
(…) The human small intestine is only a little smaller than expected from the size of our bodies, reflecting that this organ is the main site of digestion and absorption, and humans have the same basal metabolic rate as other primates in relation to body weight. But the large intestine, or colon, is less than 60 percent of the mass that would be expected for a primate of our body weight. The colon is where our intestinal flora ferment plant fiber, producing fatty acids that are absorbed into the body and used for energy. That the colon is relatively small in humans means we cannot retain as much fiber as the great apes can and therefore cannot utilize plant fiber as effectively for food. But that matters little. The high caloric density of cooked food means that normally we do not need the large fermenting potential that apes rely on.
(…) The weight of our guts is estimated at about 60 percent of what is expected for a primate of our size: the human digestive system as a whole is much smaller than would be predicted on the basis of size relations in primates.”
Another change that is not mentioned is that humans produce several times the amount of starch-splitting enzymes (useful for digesting complex carbohydrates) than chimpanzees. It’s obvious that although we share a lot of similarities with these animals, we are VERY different. We would also expect our diet to be somewhat different.
Could Humans Live on a Chimpanzee Diet?
The idea is appealing: chimpanzees live on fruit, therefore we can also live on fruit.
However, we should ask ourselves: what kind of fruits do chimpanzees live on?
“Evolutionary adaptation to cooking might likewise explain why humans seem less prepared to tolerate toxins than do other apes. In my experience of sampling many wild foods eaten by primates, items eaten by chimpanzees in the wild taste better than foods eaten by monkeys. Even so, some of the fruits, seeds, and leaves that chimpanzees select taste so foul that I can barely swallow them. The tastes are strong and rich, excellent indicators of the presence of non-nutritional compounds, many of which are likely to be toxic to humans—but presumably much less so to chimpanzees. Consider the plum-size fruit of Warburgia ugandensis, a tree famous for its medicinal bark. Warburgia fruits contain a spicy compound reminiscent of a mustard oil. The hot taste renders even a single fruit impossibly unpleasant for humans to ingest. But chimpanzees can eat a pile of these fruits and then look eagerly for more. Many other fruits in the chimpanzee diet are almost equally unpleasant to the human palate. Astringency, the drying sensation produced by tannins and a few other compounds, is common in fruits eaten by chimpanzees.”
(…) Astringency is caused by the presence of tannins, which bind to proteins and cause them to precipitate. Our mouths are normally lubricated by mucoproteins in our saliva, but because a high density of tannins precipitates those proteins, it leaves our tongues and mouths dry: hence the “furry” sensation in our mouths after eating an unripe apple or drinking a tannin-rich wine. One has the same experience when tasting chimpanzee fruits such as Mimusops bagshawei or the widespread Pseudospondias microcarpa. Though chimpanzees can eat more than 1 kilogram (2.2 pounds) of such fruits during an hour or more of continuous chewing, we cannot.
(…) The shifts in food preference between chimpanzees and humans suggest that our species has a reduced physiological tolerance for foods high in toxins or tannins. Since cooking predictably destroys many toxins, we may have evolved a relatively sensitive palate.
My Comments: Since I’ve been coming to Costa Rica, I’ve had the chance to look at what monkeys eat in the wild. The monkeys in Costa Rica are not like great apes, but fruit constitutes most of the diet of some of these monkeys.
What always puzzled me is that whenever I saw the fruits these monkeys ate, and by accident some of it was dropped on the ground, it always looked far from edible to me. Whenever I tried to eat some of these fruits, I found them to be quite repulsive.
I don’t think that my taste buds have been corrupted by the foods I’ve eaten all my life. For a modern human, I have pretty natural taste buds. And I’m quite convinced that a baby human would not enjoy many of the fruits eaten by most monkeys, and would in fact refuse to eat them.
Even Raw-Foodists “Cook” Their Foods
“It makes sense that we like foods that have been softened by cooking, just as we like them chopped up in a blender, ground in a mill, or pounded in a mortar. The unnaturally, atypically soft foods that compose the human diet have given our species an energetic edge, sparing us much of the hard work of digestion. Fire does a job our bodies would otherwise have to do.”
This last quote by Wrangham made me look at the way raw-foodist eat their foods. In my opinion, even smart raw-foodists like 80-10-10 do the equivalent of “cooking” without using any heat. Let me explain:
- We get more calories from our raw foods by making smoothies and other blended foods
- We assimilate more from our greens by blending them into soups or even juicing them
- We favor high-calorie fruits such as bananas, dates, mangoes and other tropical fruits, which have been bred to be high in sugar and low in fiber.
- We make rich dressings by blending nuts, seeds and avocados
- Some raw-foodist also ferment certain tough vegetables
Why do you think that blending is so popular in the raw-food world? Why do you think that green smoothies are such a craze? Why do you think vegetable juicing has so many fans? These are all techniques we use to get the most out of our raw foods! In other words, most people inherently understand that eating carrot sticks doesn’t work. They know that raw-foods are lower in calories, and therefore have discovered all kinds of ingenious ways to make them more digestible.
I do believe that this raw food diet CAN works when we use some of these tools. In my opinion, in would be almost impossible to live off wild foods. And I can bet you anything that anyone who eats a significant quantity of wild food in their diet gets the bulk of their calories from either cultivated fruits, cooked rice or grains, potatoes or avocados, or has access to an unnatural variety of dried “wild” foods shipped from all corners of the world.
It’s not that cooking food is one of the defining aspects of civilization. I believe that it’s the “processing” of foods that makes the difference. This includes: blending, cultivating, hybridizing, juicing, etc. Raw-foodists may just be a lot smarter by using methods that don’t create toxins that are harmful to the body when processing their raw foods.
We are civilized by nature. Even the modern raw-food diet is “unnatural”.
So my final comments on this topic are as follows:
- There may never have been a “golden age” where humans lived in perfect health eating delicious fruits and vegetables. Most likely, we come from a line of animals that ate tough and astringent fruits similar to those modern apes eat. Over time, we started to cook more and more, and learned how to hybridize plants to get sweeter and better varieties. We evolved to prefer these foods over the wild foods we formely ate. Trying to go back to wild foods simply doesn’t work.
- Cooking was probably a key element in human evolution, however it doesn’t mean we are forced to keep eating it today. Modern nutritional knowledge of calories, combined with cultivation of many varieties of sweet fruits, non-bitter vegetables and modern techniques such as blending allow us to eat a raw diet and get the best of both worlds (civilization and nature).
- We come from such a long line of sick and diseased ancestors and parents living on the low-quality, toxic Standard American Diet that a low-toxin, high-nutrient raw-based diet is definitely the way the go.
I do not believe that the research presented in the book Catching Fire really goes against the low-fat, fruit-based raw diet. However, it does show you how unsustainable most other low-calorie, high-fat raw-diets are, and how many of their claims are not based in solid science.
IMPORTANT FINAL NOTE: I don’t intend to turn this discussion into a creation vs. evolution debate. I respect everyone’s beliefs but will not let the comment section turn into a heated fight between religion and science. That is not the point of this article. The discussion is about civilization vs. nature, so please keep that in mind before posting any comment.