I’ve never been tempted to try a raw food diet, partly because I live in a chilly climate and the thought of eating cold food in the wintertime sends shivers down my spine, and partly because all the chopping, juicing, drying, soaking, and sprouting seems like a formidable obstacle. If you think cooking from scratch is time-consuming, you ain’t seen nothing until you’ve cracked a raw-food cookbook.
After reading Catching Fire: How Cooking Made Us Human by anthropologist Richard Wrangham, now I have even more reasons to prefer my food well-done.
Raw foodists often point out that humans are the only animals who cook their food -- as if this proves it’s unhealthy, or at least unnatural. Not so, argues Wrangham. Humans evolved to eat cooked food. We thrive on it. Cooking is what allowed us to transform from apelike creatures into the smartest, fastest, most dominant species on the planet.
(By the way, contemporary people on raw food diets often show decreased rates of fertility. In one study mentioned in the book, 50 percent of women on a raw food diet stopped menstruating. Given that modern raw foodists enjoy a reliable food supply and an array of labor-saving devices like juicers and food processors, while our ancestors had neither, it’s no wonder there are no traditional cultures anywhere in the world that subsist on raw food.)
What’s so special about cooking?
So how did cooking cause such a seismic evolutionary shift?
In a nutshell, you are not what you eat. You are what you digest. Raw food is harder for your body to digest than cooked food, and a greater percentage of it passes through your body unused. Cooking weakens food’s molecular bonds, allowing your gastric juices to process it more easily and efficiently. Digestion, it seems, is very costly to your body. Fewer resources devoted to digestion means more are available for other organs, specifically your brain, which is also an energy hog.
In other words, the adoption of cooking (probably discovered by accident) caused us to develop larger brains and smaller guts. Compared to most mammals, we humans have tiny mouths, teeth, and digestive systems, but significantly larger brains.
Consider our chimpanzee cousins, with their big strong jaws, which they need in order to process their raw diet. Chimps spend about half their awake time -- six hours a day -- chewing their food. The average adult human spends about 36 minutes a day doing the same. Less time spent chewing and digesting equals more time for hunting, gathering, and building civilizations.
Assembling around the fire meant humans were forced to get along and cooperate with each other, as opposed to everyone for himself. Cooking prompted us to create household economies and divide the labor. Men could spend their days hunting, knowing a meal would be ready when they got back to camp. Women could count on their mates guarding their food stockpiles from being stolen. This earliest form of marriage was, as Wrangham calls it, “a primitive protection racket.”
Not a level playing field
The most astonishing thing, to me, about the cooking hypothesis is its implication that the calorie content of a given food, as determined in a lab, is pretty much meaningless.
That’s right. Those nutrition facts on the label are only a ballpark estimate. Just as raw food takes more work to digest than cooked food, cold food costs more to digest than the same food eaten hot. Large particles are harder to digest than smaller ones. Foods eaten as part of large meals take longer than snacks. And so on. The variables are endless: even your state of mind while you’re eating plays a role in how well you digest your food, as I know from experience. People vary enormously in the efficiency of their digestive systems. The book even cites evidence that lean people routinely spend more energy on digestion than heavy people.
I've long suspected as much!
In our modern society, Wrangham observes, we’ve taken the cooking principle to its most extreme level. Our food today is so highly processed, and it takes so little effort to obtain, prepare, and digest, that we end up absorbing far more of it than we need. Hence, the obesity crisis.
It’s not an argument for a raw-food diet, but it’s one more good reason to eat the least-processed food you can manage.