Evolution: The Basis for Understanding Human Nutrition

hadza

The Hadza people of Tanzania, one of the last hunter-gatherer tribes on earth.

After my last article on traditional diets I started thinking more about the changes that have occurred to the human diet throughout our evolutionary history, and in this article I will give a broad overview of these changing dietary patterns and briefly discuss the implications for human health. For simplicity’s sake, I’ll divide human evolution into three periods, as the transitions between these eras represent the major shifts in the human diet. However, I want to emphasise that this is a broad outline, since we know that these changes didn’t occur at the same time everywhere and that some contemporary populations still haven’t made the transition from a hunter-gatherer lifestyle. However, I think this evolutionary overview of food and diet is extremely valuable as it gives us a structure to work upon when we’re dealing with human nutrition, shows us how dietary shifts impact human health, and provides many clues as to what is wrong with modern diets.

For simplicity’s sake I’ll use the term paleolithic foods to describe food that was available in the paleolithic, neolithic foods to describe food that became available after the agricultural revolution, and modern foods to describe foods that have become a part of the human diet over the last couple of centuries.

Paleolithic (~2.6 million years ago – 10,000 BP)

The Paleo Diet is based on the idea that we should eat like our stone age ancestors to optimize gene expression.Food availability
Wild plants and animals. Seafood, meats, eggs, vegetables, fruit, fungi, roots, and nuts. Although legumes are usually not included in the original/pure paleo diet, some evidence suggests that certain types of legumes were a part of the diet of some paleolithic tribes (1).

Macronutrient ratio and food intake
Varied depending on geographical location, climate, season, etc. Analysis of subsistence data for 229 hunter-gatherer societies suggests these plausible percentages of total energy: 19–35% for dietary protein, 22–40% for carbohydrate, and 28–58% for fat (2). These numbers have later been questioned by other researchers, but are generally believed to represent a fairly accurate characterisation of the hunter-gatherer diet.

Health
We don’t have data to say for sure, but it’s generally accepted that the paleolithic man was healthy, fit, and strong. This is also supported by studies of contemporary hunter-gatherer tribes, which are virtually free from the so-called diseases of civilization (3,4). While life expectancy was probably low compared to today’s standards, this is often attributed to high infant mortality, warfare, accidents, infectious disease, etc.

Agricultural revolution (~10,000 years BP)

grains-neolithic

Grains became an important staple food for the neolithic man.

Food availability
A mix of domesticated and wild plants and animals.
- Seafood, meats, eggs, vegetables, fruit, fungi, roots, and nuts.
- Grains, legumes, dairy, and other foods introduced with the neolithic revolution.

Macronutrient ratio and food intake
Varied depending on geographical location, climate, season, etc. A shift towards more grain-based diets led to a higher carbohydrate intake than in the paleolithic diet.

Health
It’s widely accepted that the neolithic revolution is associated with declining human health and a shortening of stature (4,5,6). While studies suggest that diet played a substantial role in this declining health status, we don’t have data to say much about the exact contribution. However, studies by Dr. Weston A. Price show that some traditional populations, such as the people in the Lötschental Valley in Switzerland and the Scottish and Gaelic living in the Outer Hebrides, maintained excellent health on a grain-based diet. In combination with other studies, Dr. Price’s findings suggest that some high-quality neolithic foods (especially legumes and high-quality dairy products) can be a part of a healthy diet.

Industrial revolution and the modern age (~year 1760 – today)

modern-diet

From an evolutionary point of view, these westernized foods are very recent introductions in the human diet.

Food availability
Mostly domesticated food
- Seafood, meats, eggs, vegetables, fruit, fungi, roots, and nuts.
- Grains, legumes, and dairy.
- Widespread use of refined vegetable oils, refined cereal grains, and refined sugars. New “westernized” food with an unnatural macronutrient concentration introduced in the human diet.

Macronutrient ratio and food intake
Typical western diet: 15% protein, 25-35% fat, and 50-60% carbohydrate.

Health
Modern science has allowed us to combat infectious disease in the industrialized world (What are the consequences of messing with nature’s selective processes?). However, chronic diseases that are generally considered non-communicable, such as cardiovascular disease, obesity, type-2 diabetes, and other so-called diseases of civilization, are on the rise. (Contrary to popular belief, these disorders are probably, to a certain degree, communicable by sharing of bacteria)

Human evolution and nutrition – General characteristics/notes and implications for human health.

Carbohydrate and fat content
There are no foods in the paleolithic diet that are both high in carbohydrate and fat. For the most part, this is also true for neolithic food. On the other hand, highly processed modern food often contain a potent combination of both fat and carbohydrate (usually starch or sugar).

Carbohydrate density
With some exceptions, carbohydrate-rich foods in the paleolithic diet, such as fruits, vegetables, and tubers, have a low calorie density, a maximum concentration of 23% carbohydrate, and a “high” fiber content. Cereal grains have a higher carbohydrate density than these paleolithic foods, and grain fiber is harder to digest. Modern processed sources of carbohydrate are often very high in starch or sugar, low in fiber, and high in calories compared to ancestral sources.

Palatability, reward, and satiety index
Simple, whole foods (e.g., meat, vegetables, berries) that were available to our prehistoric ancestors have a high satiety index, low reward value, and low palatability compared to modern foods (e.g., pizza, pastries). This also applies when we compare paleolithic food to neolithic food, but this difference is less pronounced. The high food reward of modern, westernized food is often considered the main reason so many people consume more calories than they need to sustain bodyweight.

Fat density
Certain foods that were introduced in the human diet with the agricultural revolution, such as butter and cream, have a higher saturated fat density than anything our paleolithic ancestors ate. The consumption of highly dense sources of fat became even more pronounced as pure fats and oils were introduced in the human diet. While not problematic per se, these products have a very high calorie density and fairly low satiety index. Also, dense sources of fat could promote the translocation of bacterial endotoxins from the gut.

Declining micronutrient density
This decline began with the agricultural revolution (e.g., on a calorie by calorie basis, grains have an inferior micronutrient profile compared to vegetables and fruits) and worsened with the introduction of highly processed westernized food (e.g., refined grains, refined vegetable oils) in the human diet. These food choices, in combination with food transport and soil depletion, have a dramatic effect on the micronutrient content of the diet.

Processing and antinutrient content
All foods in the paleolithic diet can be eaten raw and are generally low in antinutrients.
Grains and legumes require some type of processing and are high in antinutrients.  These antinutrient can have adverse effects on human health IF we don’t use traditional processing techniques (e.g., fermentation) and/or have the right types of gut bacteria to degrade the harmful compounds.
Modern foods, such as pastries, refined vegetables oils, and “junk food”, are highly processed and low in antinutrients.

Diet: Changing macronutrient composition
Protein: Hunter-gatherer diets are generally higher in protein (19-35%) than neolithic and modern diets. Also, while hunter-gatherers usually get most of their protein from animal source food, some westerners get most of their protein from inferior sources such as cereal grains. Protein has a potent effect on satiety, thermogenesis, and leptin sensitivity, and studies show that high-protein diets are great for weight loss. A low protein intake in the typical western diet could be one of the reasons so many people consume more calories than they need to sustain body weight.
Carbohydrate: Carbohydrate percentages in grain-based postagricultural diets and today’s typical western diet (~50-60%) are much higher than the average carbohydrate content of hunter-gatherer diets (22–40% for carbohydrate) (2). We know that many hunter-gatherer tribes and non-westernized populations are/were healthy on high carbohydrate diets, but they contained none of the refined grains and sugar-laden junk food that are a part of the western diet. Also, if grains were a part of the diet, they were typically processed in a different way than we do today.
When it comes to fiber, it’s generally assumed that the average fiber content in the hunter-gatherer diet is much higher than that of the typical western diet. The exact intake clearly depended on food availability, season, etc., and while the traditional diet of some indigenous people, such as the Inut, are fairly low in fiber, other hunter-gatherer tribes could have eaten more than 100 grams of prebiotics each day (7). This high fiber content, in combination with the many aspects of the hunter-gatherer lifestyle that promote a healthy gut microbiome, would have provided these primitive peoples with good gut health.
Generally, the typical western diet contain more starch and sugar and less fiber compared to the prehistoric human diet.
Fat: On average, fat intake in hunter-gatherer diets is on the high side (28–58% of energy) compared to the values currently consumed in modern, industrialized societies (~30%). As wild meats are lower in saturated fat than domesticated meats and hunter-gatherers didn’t have access to dairy products, saturated fat would generally have contributed a smaller percentage of the total fat intake in the hunter-gatherer diet compared to the western diet.

Other dietary factors that play an important role  (4)

  • Shifting sodium/potassium ratio
    High sodium and low potassium content in the typical western diet compared to the diet of hunter-gatherers.
  • Net acid load
    Estimates suggest that the paleolithic diet of East African humans was predominantly net base producing while the western diet is net acid yielding.
  • Food processing techniques
    Novel food processing techniques, such as extreme heating and pasteurization, can lead to the production of compounds such as Advanced Glycation End products (AGE).
  • Glycemic Load
    Sources of carbohydrate in the paleolithic diet have a low glycemic load compared to many of the most common sources of carbohydrate in the western diet.
  • Fructose
    Introduction of refined sugars (e.g., HFCS) has led to an increased fructose consumption.
  • Omega-3/Omega-6 ratio
    Generally, hunter-gatherer diets are higher in Omega-3 and lower in omega-6 than the typical western diet.
  • Food hygiene
    Some studies suggest that we’ve become too clean, and that we could benefit from dirtying up our diets and reconnecting with some old friends.
  • Harmful components in food
    Pesticides, antibiotics, etc. that are used in food production could reach humans.

Key takeaways

Human nutritional patterns have changed significantly throughout our evolution, with the most dramatic shifts beginning with the agricultural and industrial revolution. On one end of the spectrum we have the pure hunter-gatherer diet, composed of simple, whole foods derived from wild plants and animals. On the other end of the spectrum we have the highly processed western diet, characterized by high intakes of refined, highly palatable, and calorie-dense foods. The 10000 years that have passed since the agricultural revolution is just a small drop in the sea compared to the hundreds of thousands of years we lived as hunter-gatherers, and the preagricultural human diet could in many ways be considered the default human diet.

There are still some isolated tribes eating a pure hunter-gatherer diet, but the majority of the world’s population has now adopted the western dietary pattern. The fact that dairy products, cereal grains (especially the refined form), refined sugars, refined vegetable oils, and alcohol make up to 70% of the total daily energy consumed in the U.S., while these foods contributed 0% of the total energy in the paleolithic diet illustrates the dramatic changes that have occurred since the preagricultural era (4). Changing dietary patterns are largely responsible for the decline in human health that occurred with the neolithic revolution, and this trend has only worsened over the last couple of centuries with the introduction of refined vegetable oils, refined sugars, “junk food”, and other novel foodstuff in the human diet.

There are many important takeaways from this post. Perhaps the most essential one is realising that we’re grasping in the dark if we don’t have an evolutionary perspective on human health, as we can’t really understand how to eat and live without looking at the diets, selective pressures, and natural selection that made our species what it is today.

Practical applications

But what does all of this mean in terms of practical applications? We clearly don’t have access to the exact same food as our ancient ancestors, as there’s a big difference between the wild plants and animals available in the paleolithic and those we buy at the grocery store today. However, although they aren’t exactly the same as what our paleo ancestors ate, we do have access to meat, fish, vegetables, fruits, and other foods that were a part of the paleolithic diet. These foods lay the basis for the contemporary paleo diet, a way of eating that is based around the idea that we should emulate the diet of our prehistoric ancestors to the degree that is possible and practical in the modern world.

However, although there’s no denying that the paleo diet is a very healthy diet, I think it’s unnecessarily restrictive for most people. There’s little evidence to suggest that taking a step into the neolithic era and incorporating some legumes, high-quality dairy, and other foods that were unknown to our paleolithic ancestors will have any adverse effects on health. On the contrary actually, there are many health benefits associated with the consumption of certain types of legumes and dairy products. However, when it comes to grains there’s a lot of compelling evidence showing that a grain-based diet is not the way to go for optimal health. Some grains here and there, no problem. However, the high antinutrient content, poor micronutrient profile, and high carbohydrate content are just some of the reasons why I don’t believe in basing a healthy diet around cereal grains. The only way I see a grain-based diet as a good option is if you buy high-quality whole grains and take the time to traditionally prepare them (e.g., fermentation). And even then you would have probably been better off eating fruits, nuts, and vegetables instead.

Another thing we can learn from both evolution and modern science is that food quality matters a lot. It’s not just about the specific foods you eat, but the way they are produced, handled, and processed. This is also the area where we have completely disconnected ourselves from the traditional way of doing things, and soil depletion, grain-fed livestock, and the use of antibiotics and hormones in animals are just some of the factors that make our food inferior to those consumed in earlier times. Choosing organic, grass-fed, etc. and returning to old food practises could therefore be worth the money and time if you’re looking to optimize your health.

When talking about optimal human nutrition, there’s really no need to enter into the industrial revolution and modern age as few disagree that refined vegetable oils, refined sugars, “junk food”, and other foodstuff that have entered the human diet during the last centuries shouldn’t be a major part of a healthy diet. However, finding the right balance is definitely the key. For one person this could mean eating whatever they want for a couple of meals each week (90/10 or 80/20 rule) or for some, like me, it means loosening up on the diet when I’m at a dinner, trip, or party.


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Comments

  1. Extremely well researched, as usual. In my own studies, I’ve noticed that obesity didn’t start rising until after 1992 when the first FDA Food Pyramid was introduced and updated in 2005. Plus the grains we consume now are far different then even 100 years ago.

    I grew up in the 50s eating white bread, butter and whole milk. It was rare to see a fat person back then and in school. I don’t know when soy started being pushed as a high yield nutrient necessary for “good health” but I do know that if a rancher wants to fatten up his chickens and cattle, he feeds them soy beans.

  2. Thanks for the article. In it you mention that “other hunter-gatherer tribes could have eaten more than 100 grams of prebiotics each day” but the citation was broken. That seems like a lot to me so I would like to hear more. Any chance you could tell me where you are pulling that figure from?

    • Fixed the link :) While the numbers reported in that study (135 g inulin-type fructans per day) are on the extreme end of the spectrum, there’s no doubt that the average hunter-gatherer consumed a lot more fermentable substrates than the typical westerner (~30-35 g fiber each day). This is also the case for contemporary H-G, such as the Hadza I mentioned in the article. It’s difficult to not consume a lot of prebiotic fibers when you’re eating plenty of wild tubers, fruits and berries, veggies, etc.

      However, as mentioned in the article, there are some exceptions!

  3. Good and interesting article. Why is it that a panel of 22 experts, ranked the Paleo diet lowest of 20 different dietts back in 2011 and still is considered to be in the lower end? The ranking was done by U.S. News & World Report.

Trackbacks

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