by Bret Contreras May 05, 2014
Are we returning to our ancient ancestors way of eating? Internet search trends and the enormous traction the caveman diet has gained over the last decade (especially the last couple of years) might suggest so. The paleo diet was the most googled diet of 2013, and many strength trainees, athletes, fitness enthusiasts, and even housewives and folks who previously weren’t especially interested in nutrition and health now swear by the paleo diet as a way to build a strong, fit, and healthy body.
However, not everyone has jumped on the bandwagon; with the amount of mainstream attention and popularity of the paleo diet, criticism and controversy are also inevitable. This surge in negative press and articles out to debunk the paleo diet has been especially apparent over the last couple of months, and it even seems that we’re heading to a place where it’s cool to lash out against the very idea of eating like our hunter-gatherer ancestors. This criticism probably stems from the fact that the paleo diet goes against most conventional dietary wisdom, and that most people aren’t ready to give up grains, milk, and other common staple foods in the western diet and therefore rather mock the very idea of eating like our “simple-minded” prehistoric ancestors.
This is not going to be one of those articles. I see no point in “bashing” a diet that focuses on eating nutritious whole foods (often organic, grass-fed, etc.). However, there are some limitations and flaws of the paleo diet philosophy, and in this article I’m going to take a deeper look at one of the basic premises of the paleo diet; the idea that our genome hasn’t fully adapted to foods introduced after the agricultural revolution (sometimes characterized as neolithic foods) and that we therefore should eat the foods our paleolithic ancestors ate if we want to optimize health and gene expression.
I think few would disagree that the paleo diet is a very healthy diet. I also don’t think anyone in their right mind would classify the paleo diet as a fad diet, as it in many aspects could be labelled the default human diet. I’m a big fan of using evolution as a guide in all aspects of life, and I truly believe that we can’t really understand human nutrition without studying the way humans have been eating for millions of years and therein the selective pressures and natural selection that made the human species what it is today. However, this doesn’t mean that we have to emulate the diet of our ancient ancestors to be healthy. It seems that every time someone focuses on evolution, hunter-gatherer diets, etc., the information is automatically labelled as “paleo”. However, few people would say that an economist or engineer who studies the history of their craft believe that we should return to the old ways of doing things. It’s simply a very efficient way of finding out what works and what doesn’t and creating a structure to work upon. Like the italian philosopher George Santayana once said: “Those who cannot learn from history are doomed to repeat it.”
Let’s first define what the paleo diet is for those who aren’t familiar with the concept. The standard/original paleo diet consists mainly of seafood, grass-fed pasture raised meats, eggs, vegetables, fruit, fungi, roots, and nuts. While there’s some controversy regarding the consumption of legumes and cereal grains in the paleolithic, it’s generally accepted that these foods were not a substantial part of the diet of our prehistoric ancestors, and in addition to dairy products, potatoes, refined salt, refined sugar, and processed oils, grains and legumes are therefore excluded from the paleo diet. A couple of other things bear mentioning to really get a grasp of what the paleo diet is and how it’s practiced today. First of all, it’s well established that there wasn’t one universal paleolithic diet. The diet of both ancient and contemporary hunter-gatherer tribes depended/depend on several factors such as geographical location, season, climate, etc., and nutrient intake therefore varied/vary considerably between different tribes. However, it’s usually well accepted that legumes, grains, and dairy products are not an important part of the hunter-gatherer diet (again, some controversy especially related to legumes). Another thing that’s especially important to mention is that the modern approach to the paleo diet has evolved significantly over the last decade. When the idea of eating like our ancient ancestors first started gaining some popularity, the basic rule was that all foods introduced after the agricultural revolution should be avoided, and the paleo diet was exclusively composed of grass-produced meats, fish/seafood, fresh fruits and vegetables, eggs, nuts, and seeds. While some paleo advocates still stick to this original/”pure” diet, most of the big names in the ancestral health community now look at the paleo diet as a starting place for good nutrition in the modern world and typically acknowledge that some red wine, grass-fed dairy, potatoes, and other “novel” foods can be a part of a healthy diet. These exceptions include Mark Sisson who’s combined the best from both the paleolithic and the modern world into the primal blueprint, and Chris Kresser who talks about going beyond paleo.
Some paleo authors even claim that their version of the paleo diet is more consistent with what our prehistoric ancestors ate than the original outline of the paleo diet. This is where a lot of the recent paleo diet critiques miss the mark. If we simply look at the paleo diet on paper it looks unnecessarily restrictive. However, when we start to understand that most paleo dieters use the hunter-gatherer diet as a template rather than a strict set of rules, most people begin to accept that basing our diets around the foods we’ve been eating throughout most of our evolutionary history is probably not such as bad idea. In the sense that many of the most popular paleo gurus no longer advocate a “pure” paleo diet, it could be argued (criticized?) that the paleo diet is more of a label – or ideology/framework – at this point.
Why do some people believe that we would be better off excluding foods that our ancient ancestors didn’t eat? Although we don’t have data to really say for sure, it’s generally believed that the paleolithic man was healthy and fit – and virtually free from the so-called diseases of civilization. While the average lifespan was shorter than it is today, this decreased life expectancy is often attributed to the harsh elements our paleo ancestors faced, warfare, infant mortality, accidental deaths, etc.
Since knowledge about health and life expectancy in the paleolithic is primarily based on archeological data, it’s evident that we can’t really draw firm conclusions. However, several studies over the last centuries have unanimously shown that hunter-gatherers who are unaffected by western lifestyle are extremely healthy and virtually free from diseases such as cancer, cardiovascular disease, type-2 diabetes, and obesity (1,2,3). These healthy populations have widely different diets and lifestyles, but there are also some common characteristics that contribute to their good health. These include a moderate-high amount of physical activity (some exceptions), a paleo diet, regular sun exposure (some exceptions), “microbial exposures”, and low exposure to pollutants.
So, while diet is only one of the factors that keep these indiginous people so healthy, it’s also typically considered the most important one. The basic idea behind the paleo ideology is that the ancestral environment and lifestyle promote a normal phenotype, and that the gene-environment mismatch we’re now facing in the modern industrialized world is the primary cause of diseases of civilization.
While few people with some experience in biology and nutrition are going to disagree with the basic idea behind evolutionary mismatches and the modern suboptimal phenotype, it’s the paleo diet’s focus on agriculture that often stirs up a lot of debate. Basically, the paleo diet builds on the idea that our genome hasn’t had enough time to adapt to foods introduced after the agricultural revolution and that we therefore should eat like our paleolithic ancestors to optimize health. It’s generally accepted that the introduction of agriculture coincided with a shortening of stature and decline in human health, and it’s often believed that these changes were mostly due to the increased consumption of cereal grains and dairy products. However, while this lends support to the idea that neolithic foods are inferior to the foods we ate during the paleolithic, it doesn’t say that 10,000 years is too little time to adapt to grains, legumes, and dairy. In general, there’s a lot of controversy regarding the human genome and adaptation to new foods. Some researchers say that 10,000 years is more than enough time, while paleo advocates argue that 10,000 years is just a drop in the sea compared to the millions of years of human evolution. Anyways, that is not what i want to talk about in this article. Rather, I want to highlight the importance of the second genome in our body – the human microbiome – and the essential role it plays in the digestion and metabolism of food.
Thanks to the human microbiome project and other massive research projects around the world, we now know that trillions of microorganisms from thousands of different species inhabit the human body and that the total genetic repertoire of these germs is at least 100-times greater than that of the human host – essentially making us only 1% human from a genetic point of view (4,5). Most of these old friends live in the gastrointestinal tract, where they help us digest food and provide other essential functions that stretch far beyond the scope of our own physiological capabilities. While our human genome is “only” able to produce the necessary enzymes to break down starch, simple sugars, and most proteins and fats, the microbiome can adapt to break down a wide range of food ingredients. While we’ve learned through epigenetics that we can impact gene expression, it’s generally accepted that the human genome changes fairly slowly over time; which is why some people argue that 10,000 years is not enough time to adapt to neolithic foods. However, we’re now learning that the vastly more genetic diverse microbiome adapts rapidly to changes in diet and lifestyle. Just a single meal has an impact on the composition of microbes in the gut, and several days on a vastly different diet than the one you ate before can lead to dramatic shifts in the gut (6,7,8). The diversity, complexity, and dynamic nature of the microbiome explain why humans can be 99% different in terms of their microbial inhabitants, while it’s often estimated that we’re 99% alike in terms of our human genome.
But why does this matter in terms of genetic adaptation to neolithic foods? Just like certain genes in our human genome are needed to encode the enzymes needed to break down starch, maltose, and other nutrients, the microbiome also helps us break down and metabolize the food we put in our mouth. Just think about the process that goes on in the fermentation of milk into kefir or cabbage into sauerkraut, where bacteria are able to break down the carbohydrates in these foods. A similar process goes on in your digestive system. And this is where it really gets interesting in terms of genetic adaptation to new foods. While our capabilities to alter the human genome is limited, we can add new genetic material to the microbiome by introducing new types of bacteria. A well-known example of this type of adaptation is seen in japanese people who harbor unique genetic material in their intestinal tract that help them digest seaweed. These genes were probably acquired through eating bacteria that thrive on seaweed in the open ocean (9).
The fact that we can add genetic material to the microbiome explains why symptoms of lactose intolerance are alleviated following regular consumption of yoghurt or other types of products that provide lactose-digesting bacteria (10,11,12). Even if these critters aren’t able to colonize the GI tract, they can still transfer genes to bacteria present in the gut through horizontal gene transfer. See, unlike humans who pass DNA from parents to offspring, microbes are able to transfer genes in a manner other than traditional reproduction – and in the gut it goes on all the time. It’s important to note that this is not an overnight process as it takes time for lactose-digesting bacteria to get established in the gut. It’s also important to note that one has to consume small amounts of lactose to allow the bacteria to get a foothold.
So, you can basically manipulate the microbiome by providing new microbes (and the genetic material they hold) and/or substrates that microbes feed on. And it doesn’t only apply to lactose. Recent discoveries have shown that some microbes produce enzymes that degrade gluten (13,14,15) and phytic acid (16) – two of the most cited reasons for avoiding cereal grains. I believe the state of the microbiome largely explain why some people tolerate some foods (such as grains) just fine, while others don’t.
Does this mean that we have adapted to grains, milk, and other foods banned from the paleo diet? Not so fast… By now it’s well accepted that the western lifestyle is a master manipulator of the microbiome, and there are now thousands of studies showing that modern hygiene, processed foods, antibiotics, c-sections, etc. perturb the microbial ecosystems that live in and on our bodies (17,18,19). The westernized microbiome lacks diversity and resilience and is most likely only a faint imprint of the microbiome of our prehistoric ancestors. Loss of microbial diversity and dysbiosis (imbalance) have now been linked to a multitude of diseases and are without a doubt a driving force behind the increased rates of autoimmune disorders, food sensitivities, and food allergies now seen in the industrialized world (18,20,21). Especially relevant to this article is the increased prevalence of grain- and gluten-related disorders, which have been linked to gut dysbiosis and a loss of microbial old friends.
What this means is that even though some gut microbes are able to break down gluten and other potentially harmful components found in food, an unhealthy microbiome – rid of diversity – in combination with for example a wheat-heavy diet can be a terrible combination. This can also help explain why some non-westernized people, which have never taken antibiotics, eat “dirty” real food, regularly consume microbe-laden dirt, and are known to have vastly more diverse microbiomes than westerners, seem to maintain good health even on grain-based diets, while so many anecdotal reports from people in the modern world suggest that folks often experience better health when they reduce their consumption of cereal grains. However, it should also be noted that traditional populations typically soak, grind, ferment, or use other traditional processing techniques in order to make cereal grains easier to digest. Part of the reason many people report better digestive health when they remove grains from their diet is probably because we have strayed away from these processing techniques in the industrialized world.
Microbiome research is blooming and probiotic supplements specifically designed to deliver bacteria capable of breaking down various food ingredients in our diet might soon be available. But do we really need them? In terms of lactose intolerance we already have the means to treat this with fermented foods and probiotic supplements that contain bacteria that are able to break down lactose. Some traditionally fermented grain products probably work in the same way (depending on the bacteria present in the food and the food ingredients they degrade), but here’s the scientific research more scant. Anyways, it’s well known that traditionally fermented grains and legumes are low in antinutrients (one of the key reasons paleo advocates say neolithic foods should be avoided), and taking the time to properly prepare these foods could therefore be worth the time.
In general, eating more high-quality fermented foods (e.g., sauerkraut, greek yoghurt), fermentable substrates (e.g., resistant starch, inulin-type fructans), getting dirty once in a while, and returning to old food practises is a good idea if you want to establish a healthy microbiome. While only a few types of food ingredients are officially classified as prebiotics, the fact is that a wide range of compounds in food have prebiotic properties as as long as you harbour the right types of gut bacteria. For example lactose can be broken down by lactose-digesting bacteria in the gut if these are present, and byproducts that benefit the human host are then produced. However, the caveat is that we don’t know enough about the microbiome to accurately say which bugs are “good” and which are “bad”.
Yes, we do know that some species of bacteria such as lactobacillus and bifidobacteria are probably beneficial to human health, but we have to remember that the gut microbiota is made up of many hundreds of species of bacteria, many of which we know little about. Is the gut microbiota that results from a grain-based diet good for us? We don’t know at this point.
Also, it’s very important to note that although the microbiome can adapt to break down a wide range of food ingredients, this doesn’t mean that we should necessarily eat a lot of grains and drink milk. The fact that you’re able to digest and metabolize a food without trouble, doesn’t mean that you should necessarily eat that food. There are other legitimate reasons to decrease the consumption of grains, such as their inferior micronutrient profile compared to vegetables, fruits, and high-quality animal source foods. I rarely eat cereal grains or drink milk myself, and I don’t believe that a grain-based diet is the way to go for optimal health. However, I do believe that the paleo diet is unnecessarily restrictive for most people and that potatoes, most legumes, cacao, grass-fed fermented dairy products, wine, and some other foods banned from the caveman diet can be a part of a healthy diet.
But why did I include the word ‘unexpected’ in the title of this article? It’s certainly not unexpected in the sense that the human microbiome is uncharted territory in the paleo community; on the contrary, many paleo authors have been at the forefront in terms of highlighting the importance of the critters that live in and on us, and resistant starch, soil-based probiotics, and fermented foods are especially popular in the ancestral health community. It’s unexpected in the sense that it’s only in the last decade – and especially in the last couple of years and months – that we’ve started to understand that the gut microbiome’s role in digestion and metabolism stretch far beyond the breakdown of non-starch polysaccharides. It’s not many years ago that all the focus was on the human genome in terms of genetic adaptation to new foods, and I think no one could have predicted that the second genome in our body could be even more important in many regards. The groundbreaking new research on the microbial ecosystems that live in and on our bodies have significant implications for medicine and nutrition. In terms of adaptation to new foods, we’re now learning that although the human genome changes slowly, the microbiome can respond rapidly to dietary changes. Since there’s still a way to go before we know the details, extent, and implications, I want to emphasise that this doesn’t debunk the genetic argument of the paleo diet, it simply highlights the limitations of only looking at the human genome, and questions the belief that we can’t rapidly adapt to new foods.
One of the basic premises of the paleo diet is that we haven’t had enough time to adapt to foods that were introduced after the agricultural revolution. However, we’re now learning that although our human genome changes slowly, the human microbiome – the collective genomes of the microbes (composed of bacteria, bacteriophage, fungi, protozoa and viruses) that live inside and on the human body – can be altered fairly rapidly. Some types of bacteria have the ability to degrade gluten peptides, lactose, phytic acid, and other food ingredients that are often considered the primary “toxins” in neolithic foods.
The fact that the microbiome responds to changes in environment and lifestyle and that we can manipulate the gut microbiome by introducing new types of bacteria (e.g., fermented foods) and fermentable substrates/prebiotics, questions the idea that we need thousands of years to adapt to new foods introduced in the human diet. However, there are other legitimate reasons to decrease your consumption of milk, cereal grains, and some other foods banned from the paleo diet. First of all, widespread use of antibiotics, excessive hygiene, consumption of highly processed foods, increased rates of caesarean sections, and other factors associated with life in the modern world perturb the human microbiome, and some researchers have now begun talking about a westernized microbiome that has lost its original diversity and resilience. Another obvious issue with the modern way of life is that our food supply is extremely clean/sterile. While we’re doing everything we can to avoid rare pathogens, we’re also removing microbes that would have benefitted us in the sense that they help us digest the foods we’re eating.
Second, even though we can adapt relatively rapidly in order to digest and metabolize new foods, it doesn’t mean that we should necessarily be eating these foods. Just like with all other foodstuff, there are other concerns one has to keep in mind when designing a healthy diet, such as macronutrient composition, food quality, necessary processing, micronutrient profile, etc. Perturbations in the human microbiome and the fact that we have strayed away from traditional processing techniques can help explain the rise in grain- and gluten-related disorders and anecdotal reports from people experiencing better digestive health when they exclude cereal grains from their diet. Instead of the foods themselves, the big problem seems to lie in the way they are processed and how we have mishandled the microbial digestive machinery in our gut. By choosing high-quality products and returning to old traditional practices, such as fermentation of milk and grains, we can get optimal benefits from these foods.
There’s little doubt that modern humans now face a gene-environment mismatch in the sense that we’re not adapted for a sedentary lifestyle, highly processed foods, regular use of pharmaceuticals, little sun exposure, etc. It’s also no doubt that we can learn a lot by studying the ancestral natural environment and the way we once lived as hunter-gatherers. The great thing about the paleo diet is that it’s rich in nutritious whole foods, which are very satiating per calorie. Also, it’s low in allergens, aninutrients, and other food ingredients that often cause issues in a damaged western gut. However, it’s also unnecessarily restrictive for most people and probably works best as a starting point – rather than a strict set of dietary rules.
Name: Eirik Garnas Website: www.OrganicFitness.com Besides studying for a degree in Public Nutrition, Iíve spent the last couple of years coaching people on their way to a healthier body and better physique. I’m educated as a personal trainer from the Norwegian School of Sport Sciences and also have additional courses in sales/coaching, kettlebells, body analysis, and functional rehabilitation. Subscribe to my website and follow my facebook page if you want to read more of my articles on fitness, nutrition, and health.
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