Evidence Review: The Paleolithic Diet

16 min read

The Paleo, the Paleolithic, the hunter-gatherer, the caveman, the Stone Age, the primal diet, and others. If you have heard any of those names before, are familiar with the concept, and were persuaded because of the evolutionary arguments, then we share something in common. However, this post will review the available evidence whether the Paleolithic diet is healthy or not.

Article guide

Before I start, a lot has been written on this topic when it comes to how to eat like a caveman and why we should do so. This post, however,  focuses on the evidence and serves as an evidence-based approach and a review of all studies done with the Paleolithic diet. It also gives you the main idea what a Paleolithic diet is and why you should perhaps think about incorporating it into your diet.

Introduction

I mentioned the evolutionary argument. Yet, If I were given a McDonald’s menu every time somebody dogmatically claimed this is the last evolutionary eating pattern for our species, I would be one fat stinking carcass now, probably in a grave somewhere due to a heart attack.

Dogmatically defending views which may be constructed on totally layman arguments, as far as you know at least, is not a good thing in life, science, and is especially unwanted when talking about healthy eating.

On one hand, Paleo is a very healthy eating pattern in general, if we base our views on the Evidence-Based Food Guide. Considering it encourages a person to consume large amounts of vegetables, lesser amounts of fruit, good quality meat that should be grass-fed (ruminants) or free range (poultry, together with their eggs), and a reasonable amount of healthy oils and nuts.

It is mostly based on plant foods. Protein intake ranges between 35% but also to 65% of caloric intake – depending on personal preference. Total fat intake is estimated to be around 20-35%, again, more depending on the person.

It eliminates all processed foods, refined sugars, legumes, dairy, starches, and grains. The former two are rather obvious improvements in one’s eating patterns when we consider that they give little nutritional value and are high in calories, in comparison to the food subgroups mentioned before.

The latter is the real issue at hand. Refined grains such as white bread, white rice, and pastausually have a really high glycemic index. Our body reacts in a rather negative way due to a high glycemic index. However, there are also whole grains which have been shown to have a few advantages over their puny little-refined grain brothers. I wrote about these effects in the first post I have linked above.

Recently there have been debates whether legumes, starches, and dairy have a place in a paleolithic diet. For once, I’ll state my opinion on this matter. I have always viewed the paleolithic diet more as a conceptual framework and not so much as a you-need-to-eat-THIS-and-avoid-THAT-at-all-costs-or-you-will-die. There is no magic pixie dust in the food groups that are represented in the paleo diet.

One of the main reasons why it is so good is that it incorporates food groups which are the most nutrient dense in comparison to others and because it removes modern, processed foods. Eating meat, which is an excellent source of protein and occasionally fat, together with vegetables, which are an excellent source of vitamins and other micronutrients, as well as nuts, healthy oils, and fruit, all give you a complete macro- and micro nutrient rich diet. It removes the need for “lesser” food groups which are not as nutrient rich. However, that doesn’t mean they should not be included – starches, dairy, and legumes can and should have a place for people who lead an active lifestyle or want to gain weight.

They can be also substituted occasionally for a vegetable side dish by everyone – your body is not a frail little flower. It’s a biological machine finely crafted by a few billion years of evolution. It can survive if you eat starches and legumes instead of vegetables now and then.

A lot of available posts on the internet like to serve as romantic stories how we should eat like cavemen “Because that is how our ancestors ate”,  “it is the right thing to do”, “we are not evolved to eat grains, because they did not eat them”  we this and that and what not… The thing is, there is actually a substantial amount of direct, clear evidence that supports this eating pattern as one of the healthiest known to people (I dare not say healthiest due to lack of large scale and more long-term data). But such romantic posts could and should be a thing of the past.

When you have such direct evidence you have the right to use it in your arguments. And might I say, for once in nutritional science, the evidence is not controversial and gives straightforward results.

The controversies

Most of the serious critiques are consisted out of three streams.

  • Gene arguments
  • Differences in food quality
  • Not getting all the nutrients/getting too many nutrients due to the specifics of this eating pattern

The genes

Yes, evolutionary changes have happened since the time when we all left the African plains and went for a hike around the world.

Most known observed evolutionary changes in our species have been pigmentation changes (hair, eyes, skin), lactase retention in the intestines beyond infancy, and adaptive defenses against microorganisms (such as hemoglobinopathies and some immune system changes).

Newer research shows even more subtle genetic adaptations to dietary and other ecological niches which are adaptations to grains on a smaller scale. These include different allele frequencies associated with dependence on cereal grains as opposed to roots and tubers.

But to answer the question whether we have fully adapted to grains.

The genetic evidence is not (as) clear as some people that make a living by selling books about Paleo might be claiming. Most of the extremist statements speaking for either side are mostly consisted of a multitude of emotionally charged arguments and stretched pieces of information. A well-written post about grains and human evolution can be found on the Whole Health Source blog – along with other very well written and quality posts.

Epigenetics

Slowly there will have to be a paradigm shift in the general scientific community in the sense that, when talking about genetics, we will also have to mention epigenetics. Not much is yet known about this field as it is still in infancy. That is why a lot of attention should be directed at it.

How epigenetics has been affecting our genetic makeup and our ancestors’ adaptation to grains is a big question – while normal evolutionary changes would need a long time to manifest themselves, we now know that due to epigenetics, smaller scale adaptations may have happened a lot quicker.

This could, to a certain extent, also explain how certain ethnic groups and specific cultures could stay healthy while eating a diet that is quite different to what is perceived as healthy these days.

But Yes – the answer whether we have adapted to grains on a population level is leaning towards a “No, we have not” on a Gaussian distribution. For those of you who are interested in human evolution, the book “The 10 000 Year Explosion” (pdf) offers some interesting insights on our evolution in the recent years. 

I mentioned the population level because there are always outliers or certain subgroups of people that could be/are more accustomed to grains than others.

The food differences

This one cannot be really argued. What we are served today is incomparably worse than what the Paleolithic man had at his disposal. Artificially grown vegetables, fruit, and grain-fed meat pale in comparison to natural, organic, and grass-fed (animals) food nutrients. Kris from Authority Nutrition wrote a good article on grain-fed vs. grass-fed beef.

We can only try to strive to eat as naturally as possible – by, if capable, growing our own vegetables and fruit, and getting meat from local farmers as to be sure they were grass-fed. By doing that we can make sure the quality of our own food. The macro- and micro nutrient composition of food that has been organically produced are better in many cases. I am talking about higher vitamin, mineral, and antioxidant contents in the same amounts of plants or meat, about a better fat composition in grass-fed meats, and so on.

This analogy should give a nice explanation:

Imagine you had George and Steven. George was eating McDonald’s all day long, slurping vast amounts of Coca Cola, and munching on Snickers bars. He liked to drink a lot of alcohol and danced through rave parties while on MDMA every weekend.

On the other side, you had Steven. He was an intermittent fasting, paleolithic; all organic, grass-fed, homegrown eater that worked out furiously daily in an interval fashion, meditated every day and read scientific papers in his free time.

Who would you rather eat? Neither I hope, but I think you got the point – this can be transferred to animals and plants too.

The exclusion of certain food types

This argument talks about the deficiencies that might appear when one follows a Paleolithic style diet. I’ll keep this one short. Let me leave this quote from Staffan Lindeberg, a scientist who has written peer reviewed articles and books about the Paleolithic diet for a few decades by now.

There are no known nutrients in grains, milk or refined fats, required by humans, that are not provided by a mixture of meat, fish, shellfish, fruit, vegetables, nuts and eggs.

This is at the same time a good argument why we do not necessarily need whole grains in our eating patterns.

I did not really consider the argument about the average lifespan of hunter-gatherers serious enough and worthy of ridicule. An extensive information hub called Wikipedia.com/medicine will explain to you why their average lifespan was so short. They were lacking something really important, I wonder if you will guess without checking.

Before someone points the Tedx talk from prof. Christina Warinner who “debunked” the Paleolithic diet. Good old Robb made a very precise and correct commentary on her critiques of the Paleolithic diet.

Another common critique talks about the long-term effects of the Paleolithic diet. This is a sound critique I agree with, not in the sense of criticizing this option, but in the sense that we actually do not know what are the long-term effects of it.

And on that note.

In January of 2014, the first long-term study that lasted two years was published. I wrote about it towards the end of this post. However, we do not know what happens when people consume this diet for 40+ years on a population level. While we can make assumptions and predictions based on other similar diets, the real judgment made with scientific arguments and based on evidence cannot be given as of yet.

The benefits

The Paleolithic diet prides itself with improving outcomes in different »diseases of civilization«, among these we can find atherosclerosis, heart disease (most coronary artery disease and cerebrovascular accidents), type 2 diabetes, chronic obstructive pulmonary disease, lung and colon cancers, high blood pressure, obesity, diverticulosis, and dental caries.

It has a low amount of cholesterol-raising fatty acids and refined carbs. This can lead to a lower blood pressure, combined with a higher protein intake it can be expected to make the artery clotting properties of a Western diet less severe.

Meat has been demonized due to its connection with cholesterol raising fat intake and a nitrogen load, which could become too high with the consumption that is expected with the Paleo diet. However, the analysis of hunter-gatherer populations indicated that lean meat, similar to wild game, raised arachidonic acid concentrations and the cholesterol-lowering effect of protein. This consequentially resulted in a better serum lipid profile, one that is thought to be protective against atherosclerosis. By adding fish to their eating patterns this would be even further enhanced due to the omega-3s.

There seem to be very few obvious risks with the Paleolithic diet. The effect of a high protein intake on kidney function is debatable and is expected to be outweighed by the beneficial effects ono obesity and other health-related components.

Lean meat, fish, shellfish, vegetables, tubers, fruit, berries, nuts, and eggs can relatively safely be tried in the prevention and treatment of disease. Margarine, oils, refined sugar, and cereal grains which give 70% or more of the dietary intake for modern huma , are not an ideal food choice for long term health.

Another thing is sodium and potassium. The Paleo diet lowers the intake of both sodium and potassium compared to todays Western diet intake – it’s widely agreed that secondary prevention of hypertension should include lowering a high salt intake.

It is estimated that by decreasing the amount of salt by 3g per day (from 10g to 7g), we could prevent from 45 000 to 90 000 deaths per year in the USA alone.

The evidence

(1) A randomized controlled trial with the Paleolithic and the Mediterranean diet showed that the former was more effective in improving insulin resistance and heart disease risk factors in people with type 2 diabetes.

(2) People who had to follow a Paleolithic diet for 7 weeks observed improvements in their fasting and post-meal glucose blood levels, an increased insulin response, and considerably lower fasting plasma triglycerides.

(3) Healthy-weighted sedentary people who had to eat a Paleolithic diet for only 10 days, after a three day preparation diet which included increased fiber and K+, modestly but significantly reduced their blood pressure. Moreover, their caloric intake was controlled – they were not losing any weight yet observing these changes! Such reductions are associated with improved arterial distensibility.

This means their arteries were better at expanding and contracting under increased or decreased workload. There were also large significant reductions in LDL cholesterol (16%) and triglycerides (35%), they found no differences in HDL cholesterol. All of this was accompanied by a significant reduction in fasting plasma insulin concentrations (good) and improved insulin sensitivity (good).

(4) A randomized controlled trial included patients with either ischemic heart disease, glucose intolerance, or type 2 diabetes. They were divided into a Paleolithic and Mediterranean diet group for 12 weeks. In the Paleolithic group, glucose levels dropped by 26%, while in the Mediterranean group they dropped by 7%. Greater decreases in waist circumference were observed in the Paleolithic group (5,6 cm).

In the Mediterranean group it was lower (2,9 cm). And the most interesting thing is, the lower glucose levels were independent of the waist circumference reduction. The Paleolithic diet also appeared to be more satiating. They consumed less food during the day. This could have been a consequence of a 31% decrease in leptin levels in the Paleolithic group, and a 18% decrease in the Mediterranean one.

(5) A comparison of the Paleolithic and the standard diet for diabetes showed that the former produced lower average levels of glycated hemoglobin, triglycerides, diastolic blood pressure, weight, waist circumference, and a higher average HDL cholesterol level. Not bad when we consider the other is the STANDARD diet for diabetes, huh?

Furthermore, fasting glucose and systolic blood pressure tended to decrease more with the Paleolithic diet. It was lower in total energy, energy density, carbs, and higher in unsaturated fatty acids, dietary cholesterol, and several vitamins. Moreover, it had a lower glycemic index than the diabetic diet.

(6) In a study that lasted three months, there were noted improvements in glycemic control (0,4%) and several heart risk factors in the group of diabetes patients who consumed a Paleolithic diet, as opposed to the group who ate under the guideline of a standard diabetes diet. The Paleolithic diet was also observed to be less energy dense and more satiating. The satiety factor seems to occur in a few studies and can play a big role for certain people who would report feeling hungry when trying to lose weight.

(7) Recently, the first longitudinal study on the Paleolithic diet, was released. Loren Cordain wrote about the study on The Paleo Diet. To keep it short: a randomized clinical trial that lasted 2 years showed the superiority of this eating pattern once more.

This time it was compared to a low fat and high carb diet. It was observed to be better for losing weight at three different time intervals; three, six and twelve months. It was also better for losing body fat and waist circumference at six months. There were also greater improvements in triglycerides. Due to a smaller sample size it was hard to determine statistical significance.

However, there was a trend towards a better systolic blood pressure, blood cholesterol, and LDL cholesterol. It also resulted in a healthier eating pattern; increases in dietary protein, less carbs, more mono- and polyunsaturated fats, and with that more omega-3 fatty acids, and less omega-6 fatty acids. These changes are known to help our health by reducing the risk for the metabolic syndrome disease, different types of cancer and autoimmune diseases.

Average weight lost after the end of each study, measured in kilograms.

The last study

“But eating Paleo is really expensive”

It is possible to consume a Paleolithic diet given the constraints of the USA’s thrifty food plan, which addresses the problem of consuming a healthy diet given a budget constraint. A Paleolithic diet with the same budget is nutritionally adequate, the only shortcoming is noted in calcium, fiber, and iron. However, keep in mind that the typical Western diet fails to hit the RDA for any micronutrient for 20 to 80% of the population, depending on the micronutrient.

The constraint was set at 3,89$, if it were lifted to 4,25$ per day, it would give enough income for a Paleolithic diet that would meet all micronutrient standards except for calcium – this would represent a 9,3% necessary increase in income. Despite a lower calcium intake – net calcium balance in the body also depends on the systematic acid-base balance. The high amounts of fruits and vegetables in a Paleolithic diet are proposed to result in a positive calcium balance, despite a lower calcium intake. A high protein intake together with a high fruit and vegetable intake may improve dietary calcium absorption and whole body calcium retention.

 

That would be all

This was it. A holistic guide with scientific arguments for the Paleolithic diet about its healthiness and the most common arguments against it. Supplied with current scientific data and other high quality internet information hubs. This post should give everyone a very clear idea why the Paleolithic diet has been so talked about in the recent years and will continue to be so in the future.

For those of you who would like to know more about the paleolithic diet, I suggest the following pages:

The classical Primal Blueprint 101 from Mark’s Daily Apple.

The webpage of Robb Wolf, another leading authority when it comes to the Paleolithic diet.

And obviously, the man who is at the forefront of the Paleo movement – Dr. Cordain and his Paleo Diet Blog.

If you have not yet started eating the Paleolithic way, what is holding you back? If someone can name me a few good reasons I will give them a medal.

References used: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13]

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