By Eirik Garnas, http://www.darwinian-medicine.com/
Would you call a diet that contains 75-150 grams of carbohydrate a low-carb diet? If so, then you’re not alone. I think most people, including the vast majority of nutritionists and dietitians, would answer yes to that question.
We humans tend to base our understanding of what is natural and normal on what we can see and hear. Today, the vast majority of people eat a diet that is high in grains and sugary foods. At least this is the case in westernized societies, where pizza, bread, pasta, chocolate, and many other carbohydrate-heavy foods are routinely consumed by a substantial part of the population.
A diet that is rich in these types of foods typically contains 45-60% carbohydrate by calories, which is similar to the intake level that’s generally being recommended by government institutions that produce dietary guidelines for the public.
Given that the nutritional establishment recommends that we eat a diet in which carbohydrate is the predominant macronutrient, and most people do just that, it’s not surprising that this is the type of diet we use as our reference point when we characterize other diets.
If a diet contains more protein than the typical/”normal” modern diet, it’s labeled as a high-protein diet, and if it contains less carbohydrate, it’s classified as a low-carb diet. At first, this may seem like a reasonable way of categorizing diets; however, if we take a moment and consider the merits of this approach, it quickly becomes clear that the approach is very fallacious. It doesn’t really make sense to view nutrition in that manner.
Instead of basing our understanding of nutrition and diet composition on what is the current status quo in our society in terms of carbohydrate intake, sugar consumption, and so forth, I would argue that we should look at the totality of human evolution, and seek to establish what constitutes the evolutionary norm for our species with regards to macronutrient composition, fatty acid intake, etc.
In other words, we need to expand our perspective. If we only look at how the conditions are today, all we’ll get is a snapshot of the world, as it looks in this very second; we don’t get to see how it looked in the past. This is a problem, because if we don’t have knowledge about the past, we can’t really make sense of why things are like they are in the present.
It’s only very recently that we humans started stuffing ourselves with carbs
The weight of the evidence suggests that it’s only very recently that it became normal to eat a diet that contains 45-60% carbohydrate by calories (1, 2, 3, 4). This carbohydrate intake level may represent the norm today, but it certainly doesn’t represent the evolutionary norm for our species.
Throughout 99.9% of the evolutionary history of our genus, Homo, processed foods were nowhere to be found. Moreover, cereal grains, which are today a staple component of most people’s diet, were rarely or never consumed (at least not in large quantities) by humans until approximately 10.000 years ago.
Other carbohydrate-containing foods, such as tubers, roots, and fruit, have been a part of the human diet for a much longer time, but these foods have a very low carbohydrate density when compared to cereal grains and processed foods such as chocolate and doughnuts, which means that it would have been virtually impossible for our ancient ancestors to take in as much carbohydrate as the typical westerner does today.
Our Paleolithic forebears undoubtedly consumed honey – a very dense source of carbohydrate – if they could, but since honey is only seasonally available in some parts of the world, it’s unlikely that it made up a significant portion of our ancestors’ diet, at least not on a year-round basis.
It’s certainly possible to eat a Paleo-style diet and take in many hundreds of grams of carbohydrate each day; however, it’s not easy. You have to eat a lot of fruit and root vegetables, as well as restrict your intake of fatty and protein-rich foods. This is particularly true if you’re only eating wild plant foods, which tend to contain less sugar and starch than domesticated varieties (2, 4, 5, 6).
The evolutionary norm
If you’ve been present in the ancestral health community for some time, you undoubtedly know that some indigenous populations, such as the Kitavans on the Island of Kitava, eat a lot of carbs, in the form of sweet potatoes, bananas, yams, and other fruits and vegetables. What is important to remember, though, is that their diet is not a good representation of the type of diet that our Paleolithic ancestors ate. Yes, the Kitavans exclusively eat Paleo-foods; however, they are horticulturalists, not hunter-gatherers. They eat a lot more starchy and sugary foods than most hunter-gatherers.
This statement is supported by large studies showing that modern hunter-gatherers typically derive between 20 and 40% of their calories from carbohydrate (the exact intake varies depending on climate, geographical location, season, etc.) (1, 2, 3, 4), which is a lot less than the amounts consumed by the Kitavans, who, according to Staffan Lindeberg’s research group, derived about 69% of their calories from carbohydrate when he visited them in the late 20th century (7). It’s obviously also a lot less than the amounts consumed by most industrialized humans.
The ethnographic data that some researchers have used to establish the macronutrient intake levels of modern hunter-gatherers have been criticized by some as being imprecise and unreliable. I agree that the ethnographic record isn’t a perfect source of information about nutrition; however, after checking it against other sources, I’ve found that it provides a fairly accurate estimation of the macronutrient intake levels of indigenous people.
I see no reason to think that ancient hunter-gatherers were very different from modern hunter-gatherers with regards to their carbohydrate intake. That said, it’s obviously important to account for differences in food processing techniques and geographical locale.
A carbohydrate intake level of about 20-40% of total calories may represent the evolutionary norm for our genus, Homo. Some of our ancestors may have consumed a little more than this, and some a little less, but these folks were probably in a minority.
It’s the modern grain-based diet that represents the anomaly
Given that a hunter-gatherer way of life predominated throughout most of hominin evolution, I would argue that it’s very important to consider what our preagricultual forebears ate when we set out to categorize and design our modern diets. Instead of using the current status quo in the world of nutrition as our reference point for categorizing and structuring our diets, I would argue that it makes a lot more sense to use the Paleolithic era as our baseline, as it was during the Paleolithic that our genus and species emerged and most of the final sculpting of the human biology took place.
When compared to what is normal today, a carbohydrate intake of 20-40% of total calories is certainly a low intake; however, when compared to what was normal in the past, it’s neither a low nor a high intake, it’s a normal one. In other words, it could be argued that the term low-carb diet, as it’s commonly used today, is a misnomer. It should only be used when talking about diets that contain very little carbohydrate (<15-20% of total calories).
From an evolutionary point of view, a diet in which roughly 1/3 of the calories is in the form of carbohydrate isn’t a low-carb diet, but rather, a normal-carb diet. It’s the modern, grain-based diet that represents the abnormality. It could be classified as a high-carb diet.
The message I’m trying to get across here is not that carbs are evil. Rather, the point I’m trying to get across is that from an evolutionary point of view, it’s not normal to eat a diet that contains a very high proportion of carbohydrate relative to protein and fat. The ancestral diets that supported the evolution of the complex biological system that is the human body were “low-carb diets”, at least according to today’s conventional view.
Is this something you have to think a lot about when you make your dietary choices? No… If you eat a well-designed, species-appropriate diet, low in cereal grains, processed food, and dairy products, you’ll naturally attain a balanced intake of the different macronutrients. That said, it’s good to have some reference values in the back of your head in case you drift off course or come across someone who makes the case that it’s dangerous and unnatural for humans to eat a “low-carb diet”.
Eirik Garnas is a nutritionist, magazine writer, blogger, and personal trainer. He’s written for several different health & fitness websites and magazines, including Paleo Magazine. He is also the founder and owner of www.Darwinian-Medicine.com, a website dedicated to ancestral health, nutrition, and evolutionary medicine. Over the years he’s helped clients of all different ages, body types, and fitness levels build a healthier, stronger body.