A Sacrilegious Read

Jacob Schor ND FABNO

August 21, 2009

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A book report:

Catching Fire: How Cooking Made Us Human

by Richard Wrangham


I should hide the book I’m reading. I’m in Tacoma Washington at the annual convention of the American Association of Naturopathic Physicians.  I attend these conferences almost yearly for the continuing education programs.  I also attend the annual board and membership meeting of our oncology specialty society, OncANP, and probably most importantly to see and touch old friends.  The book I’m reading is Catching Fire: How Cooking Made Us Human by Richard Wrangham.  It is an excellently written and easy to read essay promoting what the author calls, ‘the cooking hypothesis.’


The author is a professor of biological anthropology at Harvard University and Curator of Primate Behavioral Biology at the Peabody Museum.  His book argues that learning to use and control fire and thus being able to cook food was the force that drove human evolution from early hominids, the habilines, into homo erectus between 1.8 and 1.6 million years ago.   Traditional thinking has it that humans evolved into about what we are today and then figured out how to use fire, perhaps as recently as 30,000 years ago.  If we, as Wrangham suggests, started cooking almost 2 million years ago this is a significant change and should change what we think about food and diet. 

Fire and cooked food provided an enormous evolutionary advantage.  Wrangham thinks that having protection provided by a nighttime fires allowed habilenes to sleep on the ground rather than in trees, the first primate to do so. Cooking expanded the range of foods these ancestors of ours could eat.  Cooking plants allowed better digestion and yielded more energy.  This gave our forebears an evolutionary advantage and provided the energy and nutrients required for our brains to evolve into higher energy consuming organs. 


According to Wrangham, the human body quickly adapted to eat cooked food.  Mouths became smaller, jaw muscles weaker, teeth smaller, digestive tracts shorter.  All these changes occurred as we adapted to eating cooked food 


“Cooked food does many familiar things,” Wrangham observes. “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 food.”


Once one considers Wrangham’s ‘cooking hypotheses,’ it seems so reasonable an explanation that it is hard to believe that it is really a new theory. 


Wrangham’s theory tends toward sacrilege because of what it tells us about raw food.  Our naturopathic profession has ascribed to the theory that raw food is healthier than cooked food.  The theory is that uncooked food is more natural and closer to what our bodies are designed to eat evolutionarily.  I’ve lost count of the raw vegetable platters accompanied by Ranch dressing we’ve been served over this last week.  Wrangham theory cuts apart the assumption that eating raw foods like these is healthier and tears these beliefs to shreds.


“The question,” that Dr. Wrangham poses to us is, “…what kind of diet we need…?  Are we just an ordinary animal that happens to enjoy the tastes and securities of cooked food without in any way depending on them?  Or are we a new kind of species tied to the use of fire by our biological needs, relying on cooked food to supply enough energy to our bodies?”

If Wrangham’s hypothesis is correct and at this point we have every reason to assume it is, the assumption that raw food is healthier for humans is called into immediate question.

In 2006 nine human volunteers took part in a kind of reality TV  ‘experiment’ that was produced for BBC television. These people lived in a special enclosure in an English zoo and ate a diet designed for chimpanzees.  All their food was raw.  They ate all the raw fruits, vegetables, and nuts that they could.  After a week they did add some cooked fish into their diets. “The regime was called the Evo Diet because it was supposed to represent the types of foods our bodies have evolved to eat. Chimpanzees or gorillas would have loved it and would have grown fat on a menu that was certainly of higher quality than they would find in the wild.”


I’ve mentioned this study in years past because of what happened to the participants’ cholesterol levels; they fell by 25%.  What I had not realized was that the participants also lost a great deal of weight, almost ten pounds each.  Certainly on the short term, losing ten pounds sounds like a good idea for some of us.  Consider that these people were eating 2,300 calories per day, an amount that should have maintained their weight, and you realize that something was very wrong; they were not able to harvest the calories in the food in its raw state as efficiently as if it had been cooked.  If they had attempted to continue on this diet long term they would have not had sufficient energy to meet their needs. 


There is scant research published on people who choose to eat raw food.  The most extensive is the Giessen Raw Food Study that used questionnaires to gather information on 513 Germans who chose to eat raw food for health reasons. As the proportion of raw food in the diet increased, Body Mass Index (BMI) decreased.  Average weight loss while shifting to a raw food diet was 26.5 pounds.  Of those eating a purely raw diet, almost a third suffered from ‘chronic energy deficiency.’  Among women eating totally raw diets, about 50% stopped menstruating.  A population that ceases to reproduce would certainly be at an evolutionary disadvantage.


It turns out that there are no human cultures on record that live on raw foods except for brief periods when they have no alternative.  Certainly there are instances of people who out of necessity have survived on raw foods but none do so purposefully.


Uncooked starches of course are not only rather unpalatable they are nearly indigestible yielding about 1/3 to ½ less calories.  Meat also is easier to digest and yields more energy when it is cooked.  Pretty much any food that is reduced to smaller size by chopping, blending, mashing or in any way pulverizing becomes easier to for us to digest, but the best method of processing it is with heat. 

Cooking makes food safer, reducing risk of pathogenic infection, inactivating many poisons or anti-nutritional factors innate to particular foods.


[I’m just repeating Wrangham’s arguments here.  As compelling as they are, I must be cautious about taking a position, especially considering where I am.  I haven’t even finished reading the book.  At this point though I find no argument against this hypothesis and am cautiously assuming he is right.]


There are certainly many foods in our modern diet that can be eaten uncooked.  There are few though in this category that are not the result of careful plant breeding.  Wild blueberries are the first exception that comes to my mind.  Of course I’ve always been rather partial to blueberries.  That doesn’t mean that they aren’t better tasting and more digestible when consumed as blueberry pie.  There is an obvious limit to how many raw blueberries one can eat. 


There are certain nutritional factors that are more abundant in uncooked foods that are reduced by cooking.  This loss may not be as important as the gain in caloric utilization that cooking causes.  These are interesting thoughts to contemplate. Cooking does have its downside.  Heating food reduces vitamin content.  It also creates some carcinogenic chemicals.  At the same time heating does, in certain foods, activate anticancer compounds.  Having enough calories to survive the week will probably take precedence over avoiding vitamin deficiencies months in the future.  Clearly in the short run, cooking has advantages. 


What our bodies apparently need are not ‘whole, unprocessed, unheated, raw’ food but on the other hand Hostess Twinkies are equally far from ideal.   If Wrangham’s hypothesis becomes accepted we are going to seriously rethink about what our dietary goals are.


As fascinating as this change of thinking may bring to many concepts of natural health, there is something else to contemplate here.  It is the process of intellectual change.  Who among us will be the early adopters and who will be the Luddites?


If this hypothesis does prove to be true, a great many opinions about what kind of diet is healthy will have to shift.  How do people let go of assumptions that they have considered true for most of their lives?  In our case as naturopathic physicians, the assumption that raw is better is so deeply entrenched that it acts as the unconscious basis of much of our medical practice. All of us have encouraged patients to eat less processed or raw foods.  Many of us encourage raw food cleanses.  Our advice and treatments may have been based on false assumptions.


This does not necessarily mean that these practices do not work.  We have enough clinical experience suggesting that they do.  It is our rationale for explaining their benefit that may be wrong.  It is not that raw foods are more natural.  A better possible explanation is that in some ways they are more dangerous.  The sudden loss of calories caused by switching to raw food is a shock to the system and will mobilize defensive reactions.  In a way eating raw is a caloric restricted diet, something we know that has profound biochemical effect.  Or it could be that the fully active phytochemicals found in raw plants triggers protective mechanisms that provide health benefit.  These sorts of explanations are written about under the term phytochemical hormesis. Perhaps we don’t need to change our therapies as much as our rationale for using them.


We often profess to be a scientific minded profession and claim to be open minded, adjusting our thinking to new knowledge.  Will we be able to think out of the box when it comes to such fundamental beliefs as raw versus cooked?  Or will we react to this idea that contradicts our long held beliefs by shuttering our minds to the possibility that Wrangham is right?  I hope not.


Our species face different threats today than in the past.  Advanced weapons have changed the scale of internecine conflict.  Our effect on global climate is about to precipitate earth’s next mass extinction. The greatest challenge may not be how to confront and negate these threats.  It may be to learn how to collectively and rapidly assimilate new knowledge and make intelligent and rationale decisions based on it.  Doing so is a rare skill to find in an individual.  It is more rare to find such traits embodied in a culture or society.  Yet this may be the most important thing we must learn to do both as individuals and more importantly as a society.  Learning to make smart decisions may be more challenging to do than merely learning to ‘catch fire.’