When it comes to diet, what’s common isn’t normal

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“But that’s so extreme!”

This is a common response when people first hear about the paleolithic diet, which eliminates commonly eaten foods like grains, legumes, sugar and industrial seed oils.

But while a paleo diet may seem extreme from our modern perspective, it’s actually the most “normal” diet for humans to eat.

After the Homo genus evolved 2.4 million years ago, humans lived for 84,000 generations as hunter-gatherers. We ate meat, fish, nuts and seeds, vegetables, some wild fruits when available and starchy tubers like sweet potato and yams.

Agriculture, and the mass consumption of cereal grains it enabled, didn’t happen until just 350 generations ago. And modern, refined foods like high-fructose corn syrup and industrial seed oils – which now comprise up to 30% of calories in the Standard American Diet – have only been around for about three generations.

Another way to look at it is to consider human history as a football field 100 yards long. If you started walking from one end zone toward the other, the first 99.5 yards would represent the amount of time we lived as hunter gatherers. Agriculture, and things like bread and pasta, only showed up in that last one-half yard. Coca-cola, Cheetos, energy bars and other processed foods didn’t become available until the last few inches of that final half-yard.

When you look at it this way, the diet we call “normal” today is what seems extreme and abnormal. There’s no doubt that a lot has changed for us in the past 120,000 years. Our life today would be unrecognizable to our paleolithic ancestors. But there’s one thing that hasn’t changed much over that period: our genes.

120,000 years seems like an eternity to us, but it’s almost inconsequential on the scale of evolutionary time. This means that humans are still genetically wired to live a hunter-gatherer lifestyle, and eat the same foods our paleo ancestors ate way back when.

It also means that if we stray from this evolutionary template, we’ll have problems. All animals evolved to eat a certain way. Cows are herbivores. They have small stomachs and very large intestines, which help them digest the cereal grasses they eat. Cats, on the other hand, are carnivores. They have large stomachs, to help them digest meat, but relatively small intestines because they don’t eat any vegetable matter.

If you feed a cow a meat-based diet, it will get sick, just as a cat will if you feed it grains and vegetables. Likewise, humans get sick when we eat a diet full of foods that we’re not adapted to eat.

There’s a big difference between what’s common, and what’s normal. The Standard American Diet may be what’s common for us today, but it’s far from normal. A normal diet is the one our ancestors ate for a couple million years before agriculture was invented. And it’s the diet we thrive on.

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  1. says

    Great post. Some questions/thoughts for you. I’ve read many reports where traditional cultures have indeed evolved around the foods they eat. As a very rough generalization, one could say that certain asian groups have evolved to more easily digest rice while certain European groups can better handle lactose (this is mainly from material I’ve read from WAPF). This seems to indicate that our genes can and do work on the smaller timelines (~120000 yrs), but perhaps you are saying this is insignificant when compared to our evolutionary timeline? Still, it begs the question, how far can you deviate from the evolutionary template before things go haywire? Obviously the SAD is too far.

  2. chriskresser says

    Ray: that kind of adaptation isn’t genetic. It’s based on changes in the gut flora. Studies have shown that certain species of intestinal bacteria will increase in the presence of certain foods, enabling us to digest them better. This is true for the Japanese and seaweeds, for example. It’s also true for lactose. Some people can “cure” themselves of lactose intolerance by very slowly and gradually building up to eating a reasonable amount of yogurt over time, because the yogurt alters the composition of the gut flora in a way that helps with lactose digestion.

  3. says

    Good article, Chris. I’m also enjoying your current series on healthy blood glucose levels.

    Ned Kock helpfully blogged about genetic adaption to diet at
    http://healthcorrelator.blogspot.com/2010/01/how-long-does-it-take-for-food-related.html
    and at
    http://healthcorrelator.blogspot.com/2010/04/genetic-clustering-of-metabolic.html

    It may be that it doesn’t take as long as one might think for adaptation to take place. Although ~400 years for any given tight population group still excludes all industrial food novelties.

  4. steve says

    Many are recommending a diet void of grains, sugars with carbs coming only from vegetibles, limited fruit and nuts, no dairy or industrial seed oils. What do you recommend as percentage of carbs, proteins and fats that should be consumed daily, keeping in mind a desire to keep blood sugar HbA1c low? How much protein for example, and does excess protein substantially raise HbA1c level?

    • chriskresser says

      I recommend 65% fat, 20% carbs and 15% protein as a general rule. I also advocate a paleo diet with no grains or legumes and carbs coming from safe starches and fruits (in moderation).

  5. Dana says

    “Some people can “cure” themselves of lactose intolerance by very slowly and gradually building up to eating a reasonable amount of yogurt over time, because the yogurt alters the composition of the gut flora in a way that helps with lactose digestion.”

    And… there’s not much lactose in yogurt, or none at all if it’s fermented long enough? People from dairy-eating cultures (ha) probably got fermented dairy more often than not, anyway. One other major change we’ve had in our diets in the last few inches of that football field is pasteurized dairy. If you leave it raw, it turns to yogurt almost effortlessly because the yogurt-making bacteria haven’t been boiled off.

    I’ve heard of people who switched to raw milk and their lactose-intolerance symptoms lessened or disappeared entirely. I’ve also heard of people who thought they had lactose intolerance but were actually allergic to casein. And sometimes people’s responses to dairy seem to be mediated by how the cows are fed. It seems to me that a lot of our issues with dairy are camouflaged by the weird things we do to dairy cattle and dairy foods nowadays.

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