Should You Eat a Strict Paleo Diet?

meat-vegetablesOur preagricultural ancestors ate healthy, nutrient-packed diets. Paleolithic diets were high in fiber, protein, and omega-3 and contained no highly processed foods, dairy foods, refined sugar, refined grains, or added salt. Moreover, most all of the foods on the Paleolithic menu had a high satiety index score, fairly low energy density and reward value, and low glycemic index.

There’s little doubt that if everyone in the world today suddenly adopted a diet with these characteristics, obesity rates would plummet, millions of cases of type-2 diabetes could be prevented, and numerous other chronic health disorders would start to decrease in prevalence. This statement is supported by modern scientific research, which shows that Paleo-style diets are highly effective in the prevention and treatment of several chronic health disorders, including type-2 diabetes, the metabolic syndrome, and cardiovascular disease (1, 2, 3, 4).

A worldwide transition to a diet that is more concordant with the human genetic make-up is obviously not going to happen anytime soon, in part because modern, processed foods tap into the most primal parts of our brains, induce a dopamine rush, and promote addictive-like behaviours and overeating. That said, there is some evidence to suggest that things are moving in the right direction. More and more people seem to understand that the key to good health isn’t to use technology to develop new superfoods with a carefully selected combination of various antioxidants and trace minerals, but rather to adjust our modern diet so it more closely resembles the one that supported the evolution of the complex human brain and body.

Should you strive to eat a pure Paleo diet, or are you better off adhering to a somewhat less restrictive nutritional regimen?

My overarching nutritional philosophy has not changed much over the years. I’ve always been a proponent of using an evolutionary template as the basis for designing healthy diets. That said, I think it’s very important to avoid becoming one of those people who are not open to changing their opinions when they are faced with new evidence. Over the years, I’ve adjusted my stance on some nutrition and health-related issues. When it comes to the Paleo diet, I’ve softened my stance on certain points, while the opposite can be said in other areas.

As I’ve pointed out before on the blog, I don’t believe adhering to a strict Paleo diet is the way to go for everyone. This is why I often use the term ancestral diet or evolutionary nutrition as an overaching term to describe my dietary recommendations and philosophy, rather than the Paleo Diet. I don’t have anything against the word Paleo, it’s just that people get confused if you tell them to eat a Paleo diet and then go on to recommend that they can, and perhaps even should, eat certain non-Paleo foods on a regular basis.

In this article I’ll provide a summary of the main reasons why I hold these beliefs.

I want to make it clear that the things I touch on in this article are not flaws of the Paleo diet per se, but rather a result of changes in how we humans live our lives and produce, process, and prepare our food. I strongly disagree with critics of the Paleo diet who say that we shouldn’t bother looking to our primal forefathers for advice about how to eat, since we don’t have access to the same food sources as they did anyways. To me, this argument doesn’t carry much weight. Nobody within the ancestral health community has ever claimed that it’s possible for contemporary humans to eat a diet that is perfectly identical to a hunter-gatherer diet.

Dietary fiber, short-chain fatty acids, and colonic health

A strict contemporary Paleo diet may provide suboptimal amounts of dietary fiber

I used to be of the opinion that you can achieve good colonic health on a strict, contemporary Paleo diet, just as long as you make sure to eat a lot of onions, leeks, slightly green bananas, and/or other fruits and vegetables that are rich in fermentable compounds. I still think this holds true… for some people. Others may find that they do better with some non-Paleo sources of carbohydrate as well. These differences in how people respond to the same diet can partly be explained by inter-individual variation in gut microbiota composition.

Domesticated fruits and vegetables tend to be markedly larger, lower in fiber, and higher in sugar than their wild counterparts (5, 6, 7, 8). Here’s what a paper entitled Australian Aboriginal plant foods: a consideration of their nutritional composition and health implication had to say about this issue:

Native fruits also appear to be twice as high in both carbohydrate (21 v. 9 %) and fibre (8 v. 3 %). However, because the methods used are not ideal (see above), the carbohydrate is probably an overestimate and the fibre an underestimate. One thing is certain, however: wild fruits would have given people a much higher fibre intake than we presently obtain from modern fruit varieties. If AA [Australian Aboriginal] people ate half their plant food in the form of fruit (about 180 g fruit for a 12 500 kJ (3000 kcal) diet with 20 % energy as plant food), and we use the underestimate of 11 % fibre, they would ingest about 20g fibre/d from this source alone. (6)

It can be difficult to get optimal amounts of fiber through a strict, contemporary Paleo diet, because unlike hunter-gatherers, we don’t have access to uncultivated, fiber-rich tubers, fruits, and other plant foods. Through artificial selection farmers and breeders have selected for plants that are rich in sugar and low in fiber, in part because consumers prefer plant foods with these characteristics. One of the most extreme examples may be the sweetcorn…

The most famous example of artificial selection is of course the selective breeding of the feeble teosinte plant into juicy, delicious, North American sweetcorn. In 9000 years, sweetcorn has become 1000 times larger, 3.5 times sweeter, much easier to peel and much easier to grow than its wild ancestor. It no longer resembles the original teosinte plant at all. Around half of this artificial selection happened since the fifteenth century, when European settlers placed new selection pressures on the crop to suit their exotic taste buds. (9)

Some people seem to be under the belief that you get ample amounts of dietary fiber from foods such as lettuce, tomatoes, apples, and broccoli. What these individuals fail to realise is that the quantity of Short-Chain Fatty Acids (SCFAs) – the end products of fermentation of dietary fibers by the anaerobic intestinal microbiota – you get out of leafy vegetables and modern, sugary fruit is very low when compared to what you get from more fiber-heavy foods such as wild Underground Storage Organs (USOs), legumes, and whole grains (on a gram-by-gram basis).

The question becomes: Should we seek to eat the same types of foods as our primal ancestors, or should we attempt to replicate the nutritional characteristics of their diets? Since the nutrional characteristics of modern foods differ from that of the foods our Paleolithic ancestors ate, these two things are not exactly the same.

Are potatoes, white rice, and other “safe starches” really superior to whole grains and legumes?

Within the Paleo community, the general perception is – or at least have been – that if you’re going to eat non-Paleo, starch-heavy foods, it’s better to stick with white rice and potatoes than whole grains, since the former are lower in antinutrients. Personally, I’m not convinced that this is a smart approach. On this point, I’m more inclined to agree with the conventional nutritional community, which states that whole grains are the preferred option.

One caveat is that very little is known about how different fibers affect the health of the gut microbiota and what constitutes an “optimal” ratio of butyrate to acetate to propionate, the three dominant fatty acids that are produced from the fermentation of indigestible carbohydrates in the colon. It’s certainly possible that it’s better to get your fiber from fruits, vegetables, and USOs – such as the fiber-rich tubers the Hadza eat – than grains, but as few studies have looked into this issue, it’s difficult to say for sure.

Grains induce a different fermentation pattern than vegetables, meaning that the ratio of the different SCFAs you get on a grain-containing diet may differ from the one you get on a strict Paleo diet. How important these differences are in terms of human health and longevity is largely unknown. Several studies have shown that consumption of whole grains can promote positive changes in gut microbiome composition (10, 11, 12), but since these studies don’t investigate how other foods besides whole grains affect the gut microbiota and human health, they are of limited usefulness in terms of comparing the effects of different fiber sources.

Regardless, since fiber-rich USOs and other vegetables containing ample amounts of oligosaccharides and/or non-starch polysaccharides can be hard to come by in the modern world, exclusively relying on paleo-approved foods as a source of fiber may be a suboptimal approach. If the choice is between eating a diet that contains less than optimal amounts of butyrate-boosting fermentable fiber and including smaller quantities of certain types of whole grains and/or legumes in my diet, I’m going to choose the latter.

I want to make it clear that this doesn’t mean that eating bread, pasta, or other grain-based food products for every meal is a good idea. Particularly those who are insulin resistant, don’t exercise much, and/or are trying to lose weight typically benefit from limiting their consumption of foods that are very high in starch.

All I’m trying to say is that I don’t think shunning all grains (or legumes) like the plague is necessarily the way to go. Not just because low-glycemic load whole grains such as oats, buckwheat, and brown rice are a good source of fiber, but also, as I’ll touch on next, because they, in some instances, help boost athletic performance.

Starch and athletic performance

Paleolithic humans were very physically active, but they obviously never performed sprints, heavy squats, deadlifts, and other similar exercises that many weight lifters, sprinters, and gym goers do today. It can be difficult, if not impossible, to eat a strict Paleo diet and perform optimally in these types of anaerobic, highly glycolytic activities, as the Paleo diet is low in carbohydrate-rich foods.

Athletes who only perform anaerobic exercise occasionally typically don’t require anything more than sweet potatoes, yams, and other similar starchy vegetables to fuel their training sessions; however, those who adhere to a more strenuous exercise program may find that they also need to eat some foods with a higher carbohydrate density (e.g., brown rice) to achieve peak athletic performance.

The process of generating Adenosine Triphosphate (ATP) out of fatty acids is somewhat different from that of glucose – the six carbon sugar that most people derive the majority of their energy from. Fatty acids can’t enter glycolysis, but rather break down through beta oxidation to generate Acetyl CoA, a molecule that can then go into the Krebs cycle. The electron carriers produced in the Krebs cycle are used to generate ATP in the Electron Transport Chain (ETC). Oxygen is the final acceptor of electrons in this system, meaning that the process can only run if oxygen is present.

In other words, fatty acid oxidation is not an effective energy-generating process when there is a lack of oxygen. Moreover, ATP is produced at a much greater speed during anaerobic glycolysis than during oxidative phosphorylation, meaning that during activities requiring ATP at a rate that exceeds those provided by aerobic metabolism, anaerobic glycolysis becomes important.

We can also extract energy from lipids through other means, such as by using fatty acids for the production of ketone bodies in the liver. There’s evidence to suggest that some endurance athletes do well on a ketogenic diet (13, 14); however, for more anaerobic activities, optimal performance can be very difficult, if not impossible, to attain while in a ketogenic state.

Here’s what a recent review paper had to say about the metabolism of fats during high-intensity exercise:

The major drawback in fat loading is the fact that per unit of time, more ATP can be generated from carbohydrate than from fat oxidation. When blood-borne FFA are oxidized, the maximum rate of ATP resynthesis is about 0.40 moL/min, while an aerobic or anaerobic breakdown of glycogen can generate from 1.0 to 2.0 mol of ATP/min [18,19]. During high intensity exercise, the rate of ATP breakdown is too high to be matched by the rate of ATP synthesis from FFA. This phenomenon limits the use of fat loading in sport disciplines that require high intensity efforts from the athletes. High intensity exercise also suppresses lipolysis, thereby reducing the availability of fatty acids to the muscles [20]. An increased rate of glycolysis and lactate production during exercise also hinder the oxidation of fat by reducing the entry of long chain fatty acids into the mitochondria [21]. (15)

Animal source foods

What about animal source foods? The preagricultural diets that supported the evolution of the complex human brain and body were markedly higher in protein than the contemporary Western diet (16, 17, 18). Our strong appetite for protein is imprinted into our genome.

There’s little doubt in my mind that one of the main reasons so many people experience health improvements and weight loss when they adopt a hunter-gatherer style diet is that they start eating more eggs, beef, fish, and other protein-rich whole food. As I’ve pointed out in many of my previous articles, I think the vast majority of people, in particular those who are trying to lose weight and/or grain muscle, would benefit from including more high-quality protein in their diet.

That said, since the meats we eat today tend to be inferior (from a health standpoint) to the ones our ancient ancestors consumed, we’re not necessarily best off eating as much meat as they did. When compared with game meat, domesticated meat tends to be markedly higher in saturated fat, omega-6 fatty acids, and total fat and lower in omega-3 fatty acids. This is not a good thing.

This certainly doesn’t mean that you should stop eating meat altogether, it just means that you should strive to seek out products derived from animals that have had a “good life”. Just like humans, farm animals (e.g., cows. sheep) are healthiest when they live in an environment that is compatible with their genetic make-up. If they live under conditions for which they are inadequately adapted, they get sick and accumulate fat.

What about dairy foods? I’ve made the case many times here on the blog that cow’s milk is not the health food the dairy industry claims it is. Over the years, I’ve also become more and more skeptical to other dairy foods, such as sour cream, yogurt, and cheese, in part because these  products have a less than optimal fatty acid profile, contain proteins (e.g., beta-casein) that can elicit opioid effects, and may induce a suboptimal satiety response. Also, the metabolism of lactose could trigger some unfavorable health effects.

Key takeaways

The Paleo diet is a nutrient-dense diet that has been scientifically proven to be highly effective in the prevention and treatment of several chronic health disorders. That said, some people may find that they do better on a diet that is somewhat less restrictive than a “pure” Paleo diet; not because there is something wrong with the Paleo diet per se, but rather because there have been major changes in the human condition (e.g., diet, lifestyle, food supply, environment) over the last 10.000 years.

The foods we find at the supermarket today are different from the ones our preagricultural ancestors consumed. Domesticated fruits and vegetables tend to be lower in fiber and higher in sugar than wild varieties, one of the implications being that the levels of dietary fiber you get through a strict contemporary Paleo diet may be insufficient to provide you with optimal colonic health.

As for animal source foods, the meats you find at the typical grocery store today tend to contain more total and saturated fat and less omega-3 fatty acids than the game meats our ancestors brought back to camp after a successful hunt. This doesn’t mean that we shouldn’t eat meat, it just means that we should make an effort to seek out animal products derived from grass-fed and/or wild animals. It could be argued that we should eat somewhat less meat than Homo erectus and other extinct hominin species did, in part because the meat we have access to today is not as healthy, and because we have to eat a greater quantity of plant foods than they did to obtain the same quantity of fiber and certain vitamins and minerals.

Finally, we have to account for the fact that people’s dietary needs differ depending on their lifestyle. For example, individuals who perform a lot of anaerobic exercise may find that they are unable to perform optimally when eating a strict Paleo diet.

The bottom line: The Paleo diet is a great starting place for designing a healthy diet. Some people may find that a strict Paleo diet works well for them; however, others, in particular those who perform a lot of anaerobic exercise and/or feel they need more fiber than the Paleo diet can provide, typically do better when they include smaller quantities of certain starchy and/or fiber-heavy non-Paleo foods in their diet.


  1. Jennifer says:

    Great information and insight!
    Personally my digestion improved remarkably when I switched my lunches from pasture-raised meat/poultry to pastured eggs (with vegetables of course) and when I consume one/two pieces of sprouted grain bread (Ezekiel sesame) with my dinner (mostly veggies and some pasture-raised beef/chicken). Also, yes, I have more energy for athletic performance. Boom! 🙂

  2. I seem to do best if I skip most grain products with the exception of rice. Wheat, in particular, tends to put weight on me. That doesn’t mean I never touch it. I don’t think it’s a good idea to be totally inflexible about any diet other than those designed for severe health issues. I do occasionally eat a piece of buttered toast or a small piece of special-occasion dessert. I’m probably fortunate in that I don’t particularly care for pasta dishes or pizza. That makes it a lot easier to remain mostly Paleo (about 80/20), which works well for me.

    • Sounds like a reasonable approach, Shary.

      I don’t eat much wheat products either. If I need some extra carbs I’d rather go for something like brown rice.

  3. Alessio says:

    While I don’t strictly agree with
    It has some tought provoking points.
    Furthermore, I’m starting to doubt whether domesticated fruit and vegetables are really a far cry from the wild counterpart, as touted so far. For example, domesticated apricots are higher in fiber and less in sugar than the wild ones. There’s only little anedoctal evidence behind this. The linked studies about the alleged benefits of whole grains don’t show such a good evidence.
    Anyway, I think we should put together ALL the pieces of the puzzle, otherwise hemlock would be good for you because of its phytochemicals and mineral content. I wrote an article about gluten degrading bacteria from Rothia family that are harbored on a gluten laden diet, and they are linked to scary stuff like pneumonia and endocarditis.
    Besides, gluten triggers leaky gut in EVERYONE, and the “healthy” control group shows even more leakiness than celiacs in remission on a gluten free diet.
    And gliadin is just one of the thousands prolamines in grains.
    Antinutrients may be overhyped in some way but on the other hand they are not harmless either.
    Since we don’t know exactly what is the “right” microbiome, I would be really careful to use articles about the benefits of whole wheat.
    Inuit don’t eat as much fibers as Hadza, but they are lean and healthy as well.
    Moreover, you yourself linked a study a while back about a new discovered bacteria that produces butyrate from lysine metabolism. And beef is the major source of lysine, that triangulated with the adjusted PDCAAS protein score, suggests at least that the fiber stuff may be overhyped.
    I don’t claim that fibers are not crucial for health, but I don’t buy that we can’t live well without grains either.

  4. Alessio says:

    Hey, BTW, here’s a study
    Maybe too many fibers can be detrimental to an already inflamed gut.
    However, grains themselves are mostly to blame for gut inflammation, and the study further enlights that whole grains are not exactly a good idea as fiber source.
    Since the evolutionary evidence shows many cultures eating many fibers, it’s most likely that are indeed grains to blame once again. They inflame the gut and eating a lot of fibers wreaks a further havoc.
    At least, This is my perspective…


  1. […] Should You Eat a Strict Paleo Diet? — Eirik Garnas […]

  2. […] I think most ancestral health enthusiasts would agree, the Paleo template is the best starting place for designing a healthy human diet. By looking at nutrition and health through the lens of […]

  3. […] I’ve pointed out here on the blog before, I don’t think eating smaller amounts of whole grains such as oats, brown rice, and/or […]

  4. […] to that person’s needs, health condition, and activity levels. Some people may find that they do better on a diet that contains small quantities of starchy and/or fibrous grains or legumes than on a […]

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