Diet

various-foodsFor the majority of people who live in industrialized nations today, food procurement is synonymous with a quick trip to one of the many grocery stores located in the vicinity, where foods from all over the world and of all shapes and sizes are conveniently lined up for the customers.

If you circle the outer isles of the store, you’ll typically find fresh fruit and vegetables, lean meats, and other unprocessed foods, but if you venture down the middle aisles, you’ll mostly see highly processed food products, often made up a mix of sugar, flour, salt, and refined fat. In a mere 15 minutes or so you can get a hold of everything you need for the next several days, get back in your car, and drive home to your warm and comfortable home.

Few of us probably go around the supermarket thinking about how abnormal and novel this way of doing things really is.

Preceeding the Agricultural Revolution, which started approximately 10.000 years ago, all humans lived on a diet of wild plants and animals, and prior to just the last couple of centuries, highly refined and processed foods were not a part of the human diet anywhere.

The Original Human Diet

When the human and chimpanzee lineages diverged millions of years ago, the dietary path of hominins also split from that of our chimp relatives. It’s believed that the “Last Common Ancestor (LCA)” of chimps and humans – a hypothetical ape-like creature that lived in Africa – primarily ate fruit and some other plant foods, with a small additional contribution from animal source food (1). As hominins began on the bipedal journey and after a while started moving about the African savanna, new food sources – such as Underground Storage Organs (USOs) – most likely started to become an increasingly important part of the diet (2).

For millions of years, a plant-based diet continued being the available choice for hominins, but about 2 to 3 million years ago, several lines of evidence indicate that there was a gradual shift in subsistence strategy (1). This first major dietary transition is characterized by an increasingly important role of animal foods in the diet, a shift that had a profound impact on the evolution of human bodies and lifestyles. Hunting and scavenging gradually became a more important part of our ancient ancestors’ subsistence mode, and with the evolution of our genus, Homo, the hunter-gatherer lifestyle as we know it today really started to take form.

Since it’s difficult to acquire precise data about what our early Paleolithic ancestors ate, we should be cautious about drawing firm conclusions. What we do know is that when hominins migrated out of Africa and into other parts of the world, they had to adapt to new habitats, climates, and diets, and as such, there clearly wasn’t one universal Paleolithic diet consumed by all tribes.

Both the genetic data and recovered fossil evidence indicate that all living members of our species (Homo sapiens sapiens) share a common ancestor that lived in Africa 200.000 years ago (3). 50.000-100.000 years ago, our primal ancestors started migrating out of this original habitat, slowly colonizing the rest of the world. This journey marks a profound moment in the evolution of the human diet. Up until that time we had relied on what the African savanna provided of wild plants and animals, but we now started occupying new ecosystems around the world.

Although this journey out of Africa had a profound impact on the dietary road of man, the “basics” remained the same all over the world. Hunter-gatherer diets often differ markedly in terms of plant-animal subsistence ratio, carbohydrate percentage, etc., but they all consist exclusively of wild plants and animals, including meat, seafood, fruits, nuts, vegetables, and honey (4). Legumes and wild grains also made a contribution to the diet in certain Paleolithic populations, but they were rarely – if ever – eaten as staples (5, 6). Subsistence data from 229 hunter-gatherer societies suggest the following plausible percentages of total energy from the different macronutrients: 19–35% for protein, 22–40% for carbohydrate, and 28–58% for fat (7).

A rapid dietary shift: From meat, tubers, and fruit to Big Mac’s, pizza, and doughnuts

The gradual increase in meat consumption that occurred about 2-3 million years ago is an important moment in the evolution of the human diet, but compared to the emergence of animal husbandry and farming that came with the Agricultural Revolution ~10.000 years ago, it could be argued that it fades in significance. Up until that point, a forager lifestyle had been the default way of life for hominins, and over millions of years, the human digestive system, metabolism, and physiology had evolved through natural selection to “match” a diet of wild plants and animals.

As agriculture rapidly swept the globe, humans started to settle down into larger communities, and domesticated plants and animals started becoming an increasingly important part of the diet. This lifestyle transition marks the first major step towards today’s the modern western lifestyle as we now know it, and many would say it counts as one of the greatest achievements in human history. However, the change wasn’t without its consequences. Several lines of evidence show that this first epidemiological transition adversely affected many aspects of human health (2, 8, 9). A lot of this was due to the new and often unsanitary living conditions, which were the perfect breeding ground for infectious diseases.

A shortening of stature, worsened dental health, and other diet-related problems also accompanied the Agricultural Revolution, either at first or gradually (2, 8, 9). All of these problems were largely the result of a transition from a Paleolithic diet to Neolithic diet, a diet that in comparison was low in many vitamins and minerals, high in starch, and high in antinutrients and novel dietary components (2, 8, 9). This dietary transition undoubtedly resulted in changes to the microbiome – especially oral and gut – and altered gene expression patterns. Suddenly we collided with a diet that natural selection had never adapted us for.

It’s important to note though that although the data clearly show that the change in diet that accompanied the Agricultural Revolution affected human health, many other aspects of our lifestyle changed during this time as well, meaning that it can be difficult to know the significance of the dietary transition as it relates to human health. Also, studies of traditional, non-westernized populations – such as those carried out during the 20th century by Dr. Weston A. Price – suggest that it’s possible to stay free from many of the so-called diseases of civilization while eating diets high in grains and/or dairy (10). The important thing to remember though is that these populations ate foods of very high quality. Also, they put far more emphasis on traditional processing techniques, such as soaking, fermentation, and sprouting, thereby removing many antinutrients and creating end-products that had a more similar nutrient composition to the types of foods consumed by our Paleolithic ancestors.

The Industrial Revolution marks the beginning of the next major dietary change in human history, a transition characterized by the development of new manufacturing methods that allowed us to mass-produce refined grains, vegetable oils, and refined sugar. As the decades and centuries have passed since the initiation of this new food system, new food items – that our ancient ancestors probably wouldn’t have recognized as food – have made their way into grocery stores and supermarkets worldwide, and a whole new “junk food” industry has rapidly emerged. Over the same time period we’ve distanced ourselves more and more from nature – and hence the animals and plants our food comes from. Today, many of us just go into the store and pick up a nicely packaged piece of meat or a box of crackers, while not really giving any thought to where the things we buy really come from.

Several key aspects of our diet have changed since the preagricultural days, changes that essentially boil down to the following: New types of foods have been introduced into the human diet, and the quality of our food has declined.

… in the US, 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. As pointed out by Cordain et al, these types of foods would have contributed little or none of the energy in the typical preagricultural hominin diet (11).

Here are some general characteristics of western diets that describe the changes that have occurred since the Paleolithic era:

Too much

  • Starch
  • Sugar
  • Omega-6
  • Sodium
  • Saturated fat (?)

Too little

  • Fermentable fiber
  • Omega-3
  • Antioxidants
  • Protein
  • Most micronutrients

Too new

  • Trans fats
  • Certain antinutrients
  • Other “novel” food components (e.g., hormones and bio-active peptides in milk)

This orchestra promotes inflammation and disease through alterations of the gut microbiome and expression of genes in pathways related to chronic disease (12, 13, 14, 15)

5 reasons why ancestral human dietary patterns serve as a good template for designing a healthy diet in the 21st century

So, it’s no question that to understand how to eat healthy in the 21st century, we have to look back at our evolutionary past. Let’s go through some of the fundamental reasons why a Paleo-type diet is so great.

1. Millions of years of human evolution shaped our dietary needs

When researching the connection between nutrition and health, many would say that the first step is to go for the randomized controlled-trials, meta-analyses, and systematic reviews on the subject you’re interested in. After all, these types of studies are considered the gold standard of nutritional science. However, although RCTs and comprehensive reviews are absolutely invaluable when digging into nutrition and health topics, the problem with initiating the search for answers this way is it can often lead us astray.

One of the primary reasons there’s so much confusion and debate about nutrition is that there are a thousand different ways to look at the science/literature. Someone who’s drawn to the vegetarian movement will quickly focus on the studies that seem to support his cause, while those who favor a very low carb diet will point out the dozens of trials that seemingly support their ideas.

Even someone with no apparent preconceived notions can quickly be led astray and come to the wrong conclusions by looking at the research. Let’s take a subject like saturated fat for example. On the one side, there are plenty of seemingly good studies showing that a diet high in saturated fat can trigger low-grade chronic inflammation, while on the flip side there are also several reports indicating that saturated fat consumption is not linked with higher risk of atherosclerosis, heart disease, and all the other conditions butter and lard have been blamed for. The reason for these conflicting results often boils down to differences in study design and methods, and it can often be difficult to separate what is good and bad research. Without a guiding framework to help us make sense of things, we’re grasping in the dark.

So, what is this guide we need to make sense of nutritional science? Evolution, of course!

By looking at how we’ve eaten for millions of years, how our brains and guts have evolved, and how nutrition transitions have impacted human health, we establish the foundation we need to design a healthy diet in the 21st century. It’s not always easy to decipher our evolutionary history in such a way that we can draw concrete conclusions, but even by just getting a fraction of the answers we are looking for, we can begin to make sense of why things are like they are. With this evolutionary perspective in mind, we suddenly have a base to build our ideas upon.

Darwin didn’t focus much on nutrition and exercise, but he unknowingly gave us many of the tools we need to be healthy and fit in his book “On the Origins of Species”. By combining his ideas on evolution and natural selection with the science on epigenetics and microbiomes, it’s usually possible to predict what nutrition studies will show even before they have been done. That doesn’t mean doing and reading research is a waste of time – of course not, but because evolution is the foundation that supports everything else, having a basic understanding of evolutionary biology is far more powerful than any RCT or comprehensive review will ever be.

Over millions of years of life as foragers, natural selection shaped the genome that we to a large extent still carry with us today. The data consistently show that we are still very much stone agers from a genetic perspective (16, 11). The dietary changes that began with the agricultural revolution – and even more so with the industrial revolution – are extremely recent on an evolutionary time scale. 10.000 years is just a blink of an eye from an evolutionary perspective.

Certain genetic adaptations, such as increased frequency of lactase persistent alleles and alterations of the gut microbiome, have allowed us to tolerate more “neolithic foods”; but we are clearly not well-adapted to the grain-based, starchy diet most people consume today. Healthy, non-modernized populations often prepared/processed grains and dairy in such a way that the end products were lower in carbohydrates and antinutrients, but sadly we’ve now abandoned many of these techniques. Traditional processing methods such as soaking and fermentation should be employed if grains and dairy contribute a large part of the diet, but even then we’re probably best off limiting our consumption of these food groups.

2. Populations eating paleolithic, hunter-gatherer type diets are extremely healthy

kitava

Superb health among the Kitavans on the Island of Kitava. – The Kitava Study, Staffan Lindeberg

When exploring the health effects of the Paleo Diet a good way to start is to look at the people who actually eat this type of diet. Studies consistently show that hunter-gatherers and other non-westernized populations eating Paleolithic diets are virtually free from cancer, heart disease, acne, inflammatory bowel disease, and several other chronic disorders that are extremely common in the modern world (11, 17, 18). Those who transition from eating natural food to processed and refined food experience a rapid decline in health (11, 18).

Although the macronutrient ratio and food composition of the diet clearly influence health, bodyweight, and longevity, studies show that ancestral populations have thrived on both high-carbohydrate and high-fat diets (11, 17, 18).

The average lifespan of hunter-gatherers isn’t that long, but that’s not due to high cancer rates and cardiovascular diseases, but rather because of little access to modern medicine (19). In the industrialized world, public health advancements and medicine have given us the opportunity to profoundly decrease infant mortality and prolong the lives of old and sick people. We live longer, but we aren’t healthy.

Also, the fact is that when we look at the life expectancy of an adult hunter-gatherer, the stereotypical image of nasty, brutish, and short lives doesn’t reflect reality. A compilation of data on hunter-gatherer societies suggest that modal age of adult death is about seven decades (adaptive life span of 68-78 years), and contrary to most westerners, these people tend to be healthy all the way up to old age (20).

But as any scientist would point out: Despite the consistent nature of the studies on populations eating ancestral diets, they don’t prove a causal relationship between diet and health, as there are certainly many other factors beside diet that contribute to the good health of hunter-gatherers. So, let’s take a look at intervention studies to see what happens when westerners give the Paleo Diet a try.

3. Intervention studies show that a Paleo Diet is superior to other “healthy” diets

An evolutionary perspective on nutrition and data on hunter-gatherers provide a good foundation, but to really establish cause and effect, we need to dig into the intervention studies done on the Paleo Diet. Sadly, at the moment, there are “only” about a dozen of these studies looking into the effects of a paleolithic diet on fat loss, insulin sensitivity, and/or other markers of health. It’s difficult to get funding for these types of trials, especially since a Paleo Diet goes against most of what the official dietary guidelines in most countries tell us to eat.

Studies where westerners are put on a paleo-type diet consistently show that this type of dietary pattern has beneficial effects on fat loss, insulin sensitivity, and several other markers of health (21, 22, 23, 24, 25, 26, 27, 28, 29). The problem isn’t that the results from these studies aren’t convincing (they are), it’s that at the moment the studies are too few and too small to make an “impression” on the conventional nutritional community. Research funds allocated to Paleo Diet studies are just a drop in the pond.

Swedish scientists have been pioneers in this field. Hopefully more will follow…

Let’s do a run-down of the 4 randomized-controlled trials that have tested the Paleo Diet against other healthy diets:

  • In a randomized cross-over study, 13 patients with type 2 diabetes, 3 women and 10 men, were instructed to eat a Paleolithic diet based on lean meat, fish, fruits, vegetables, root vegetables, eggs and nuts; and a Diabetes diet designed in accordance with dietary guidelines during two consecutive 3-month periods. Over a 3-month study period, a Paleolithic diet improved glycemic control and several cardiovascular risk factors compared to a Diabetes diet in patients with type 2 diabetes (26).
  • Twenty-nine male IHD patients with impaired glucose tolerance or diabetes type 2, and waist circumference > 94 cm, were randomized to ad libitum consumption of a Paleolithic diet (n = 14) based on lean meat, fish, fruit, vegetables, root vegetables, eggs, and nuts, or a Mediterranean-like diet (n = 15) based on whole grains, low-fat dairy products, vegetables, fruit, fish, and oils and margarines during 12 weeks. A Paleolithic diet is more satiating per calorie than a Mediterranean-like diet (27).
  • Twenty-nine patients with ischaemic heart disease plus either glucose intolerance or type 2 diabetes were randomised to receive (1) a Palaeolithic (‘Old Stone Age’) diet (n = 14), based on lean meat, fish, fruits, vegetables, root vegetables, eggs and nuts; or (2) a Consensus (Mediterranean-like) diet (n = 15), based on whole grains, low-fat dairy products, vegetables, fruits, fish, oils and margarines. A Palaeolithic diet may improve glucose tolerance independently of decreased waist circumference (28).
  • Seventy obese postmenopausal women (mean age 60 years, body mass index 33kg/m2) were assigned to an ad libitum PD or NNR diet in a 2-year randomized controlled trial. A PD has greater beneficial effects vs an NNR diet regarding fat mass, abdominal obesity and triglyceride levels in obese postmenopausal women; effects not sustained for anthropometric measurements at 24 months (29).

4. A properly designed Paleo Diet has all of the characteristics of a diet that makes you healthy and lean

If you have a basic understanding of human nutrition, you don’t even have to look at the studies to understand that the Paleo Diet will be a great choice for people who want to improve their health and/or lose weight. Let’s look at some of the key facts.

  • A “typical” Paleo Diet is high in protein and fiber and relatively low in carbohydrate.
  • The Paleo Diet is devoid of trans fatty acids and refined sugars.
  • All of the plant foods (fruits, vegetables, etc.) allowed on the Paleo Diet have a maximum carbohydrate concentration of approximately 23% (17).
  • The Paleo Diet is extremely nutrient-dense (4).
  • All of the foods allowed on the Paleo Diet have a low-moderate reward value, low-moderate energy density (honey and very fatty meats being the exception), and high satiety index (they fill you up).
  • The Paleo Diet is low in antinutrients.

When we combine these things, we get a diet that has all of the qualities that science tells us make you fit and healthy. After all, a paleolithic, hunter-gatherer type diet consists of the types of foods we’ve been consuming for millions of years, so there’s not really a surprise that we’re well adapted to eat them.

5. Foods that are not allowed on the Paleo Diet tend to have characteristics that make the inferior to “Paleo foods”

If there’s one thing the evolutionary perspective on human nutrition teaches us, it’s that most of the food groups that have been introduced since the agricultural revolution come with some potential downsides; at least when they are not prepared using traditional processing techniques.

  • Grains are extremely high in carbohydrate compared to ancestral foods and come with a robust dose of antinutrients and proteins that are often problematic (17, 30, 31, 32, 33, 34). The human genome has had scant evolutionary time to adapt to grain-based, starch-heavy modern diets and the secondary metabolites found in cereal grains. The gut microbiome change much more rapidly in response to dietary alterations than the human genome, but these adaptations may not be sufficient to eliminate the adverse effects of novel dietary components in grains. Also, widespread use of broad-spectrum antibiotics, hygienic living conditions, c-sections, and many other factors associated with the western lifestyle have led to a dramatic loss of microbial “old friends” and an epidemic of gut dysbiosis, which means that people are less likely to possess a gut microbiota that is well-adapted to a grain-based diet.
  • Dairy milk contains hormones and bio-active peptides that are actually meant to boost the growth of calves (35, 36). Modern processing techniques (e.g., pasteurization, homogenization) are problematic (36).
  • Butter, GHEE, and oils are extremely calorie-dense compared to anything we’ve been eating throughout most of our evolutionary history.
  • A high intake of highly processed foods, such as pizza, pastries, and all the other products we’ve designed for ourselves only leads to one thing: Overweight, chronic low-grade inflammation, and metabolic havoc. These types of foods have a nutrient composition that doesn’t resemble anything found in nature.

All of this doesn’t mean that you have to ditch all of the cheese, butter, wine, and dark chocolate from your diet and stick to a strict Paleo Diet. However, there’s no doubt that primarily eating from the food groups that have been with us throughout most of our evolutionary history is the best way to go.

Practical applications

General recommendations:

  • Use the Paleo template (meat, seafood, eggs, vegetables, healthy fats, fruit, roots, and nuts) as your starting point for designing a healthy diet.
  • Add in some low-glycemic index legumes (e.g., lentils) and/or whole grains (e.g., oats) if you feel you require more starch (some athletes need more carbohydrate than the Paleo diet provides) and/or fiber.
  • Include plenty of fermentable fibers (e.g., leeks, onions) in your diet.
  • Regularly eat fatty fish, organ meats, and/or other foods high in omega-3.
  • Choose wild, organic, and/or grass-fed food when possible.
  • Intermittent fasting comes with several possible health benefits and is a viable nutritional strategy for those who find it fits their lifestyle.
  • Don’t look at it as a “diet”, but rather as a lifelong way of eating.
  • Each person’s goals, activity level, and health condition have to be considered when food choices, macronutrient ratio, etc. are to be determined.

 

 

Picture: Creative Commons picture by Didriks. Some rights reserved.

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