The Paleo problem: Examining the pros and cons of the Paleo Diet. | Precision Nutrition

The Paleo problem:
Examining the pros and cons of the Paleo Diet.

By Brian St. Pierre


Unless you’ve been living in an actual cave, you’ve probably heard all about the Paleo – or “caveman” – diet.  Maybe you’ve even tried it. A little meat here, some fresh veggies there. Perhaps going grain- or processed-food-free. It’s a cool idea that captures the imagination. But is it healthy? And does it work? That’s what we’ll explore in this article.

What we’ll cover

In this article, we’ll give you a definitive guide to the Paleo diet.


  • We’ll define just what “Paleo” refers to.
  • We’ll explain what’s so special about hunter-gatherers.
  • We’ll review how and what ancestral-style eaters actually do.

Then, we’ll explore the ideas and evidence critically.

  • What does Paleo promise?
  • What evidence supports ancestral-style eating?
  • What might cause our chronic 21st century health problems?
  • Is the Paleo diet truly primal?
  • What does our GI tract tell us?

Finally, we’ll give you the all-important conclusion:

  • What should YOU do with all of this?

“Paleo” defined

The Paleo, or primal, diet is based on two central ideas.

  1. We adapted to eat particular kinds of foods.
  2. To stay healthy, strong, and fit — and avoid the chronic diseases of modernity — we need to eat like our ancestors.


A brief history of eating

Our oldest cousins, the earliest primates, lived more than 60 million years ago. And, just like most primates today, they subsisted mainly on fruit, leaves, and insects.

About 2.6 million years ago, at the dawn of the Paleolithic era, things began to change.

Our early human ancestors started rockin’ the opposable thumb and big brain adaptations. They started using stone tools and fire, and, as a result, slowly changed their diet.

By the time truly modern humans came on the scene about 50,000 years ago, our ancestors were eating an omnivorous hunter-gatherer diet.

The basic Paleo diet

And thus we arrive at a model of a Paleo diet that includes:

  • animals (meat, fish, reptiles, insects, etc. — and usually, almost all parts of the animals, including organs, bone marrow, cartilage, and organs)
  • animal products (such as eggs or honey)
  • roots/tubers, leaves, flowers and stems (in other words, vegetables)
  • fruits
  • nuts and seeds that can be eaten raw

Recently, many Paleo proponents have suggested that eaters start with the above, then slowly introduce grass-fed dairy (mostly yogurt and other cultured options), and small amounts of “properly prepared” legumes — meaning legumes that have been soaked overnight.

What’s so special about hunter-gatherers?

About 10,000 years ago, most of the world figured out agriculture. And thus, we moved from the Paleolithic to the Neolithic period.

Planting and farming provided us with a consistent and relatively reliable food supply, without which civilization could never have developed.

Yet the 10,000-year time frame since the dawn of the Neolithic period represents only about 1% of the time that we humans have been on earth.

Many people believe that the change from a hunting and gathering diet (rich in wild fruits and vegetables) to an agricultural diet (rich in cereal grains) gave rise to our modern chronic diseases such as obesity, diabetes, and cardiovascular disease.

This is a fundamental tenet of the Paleo Diet, and a big reason why proponents say we should return to the meat and produce-based diet of our past.

How do “ancestral eaters” fare?

Of course, while we have extensive skeletal remains, cooking sites, and other types of evidence, we don’t have detailed medical records of our hunter-gatherer hominid ancestors.

However, we do have real live sample populations that we can look at.

A diverse dietary world

The very few surviving hunter-gatherer populations subsist on a wide variety of diets, from the “nutty and seedy” African !Kung, to the root vegetable-eating Kitavans near Papua, New Guinea, and the meat and fat-loving Inuit of the Arctic.

These foraging diets are diverse and probably reflect the widely varying diets of our prehistoric ancestors, simply because what people ate depended on where they lived: mostly plant-based (in the tropics), mostly animal-based (in the Arctic), and everything in between.

However varied their diets across the globe, most Paleolithic humans likely consumed about three times more produce than the typical American.

And when compared to the average American today, Paleolithic humans ate more fiber, protein, omega-3 fatty acids, unsaturated fat, vitamins and minerals, and much less saturated fat and sodium.

Hunter-Gatherer Diets

Image source: Jen Christiansen (Scientific American)

A modern example

The residents of Kitava Island, off Papua, New Guinea, are probably the most famously researched modern hunter-gatherer population.

According to Dr. Staffan Lindeberg, who’s extensively studied their habits, Kitavans live exclusively on:

  • starchy root vegetables (yam, sweet potato, taro, tapioca);
  • fruit (banana, papaya, pineapple, mango, guava, watermelon, pumpkin);
  • vegetables;
  • fish and seafood; and
  • coconuts.

Kitavans are healthy and robust, free of obesity, diabetes, heart attacks, stroke, and acne — despite the fact that most of them smoke!

Things are looking good for eating like a cave dweller.

What Paleo promises

The main idea of a primal diet — as you’ve probably gathered (no pun intended) — is that our ancient human genetic “blueprint” doesn’t match our current 21st century diet and lifestyle.

As a result, our health and wellbeing suffer.

The Paleo diet also makes some key evolutionary assumptions:

  • Paleolithic hunter-gatherers were robust and healthy; if they didn’t die young from accident or infectious diseases, they lived about as long as we do now.
  • When Paleolithic hunter-gatherers shifted to Neolithic agriculture, they got relatively sicker, shorter, and spindlier.
  • Modern hunter-gatherers are healthy, and their health declines when they switch to a modern diet.

What’s the evidence?

While a case can be made for this evolutionary trend, as a matter of fact, hunter-gatherers were not pristine models of health.

To begin with, they certainly harbored various parasites. They were also subject to many infectious diseases.

What’s more, a recent study in The Lancet looked at 137 mummies from societies ranging all over the world — from Egypt, Peru, the American Southwest,  and the Aleutian Islands — to search for signs of atherosclerosis.

They noted probable or definite atherosclerosis in 47 of 137 mummies from all four geographical regions, regardless of whether the people had been farmers or hunter-gatherers, peasants or societal elite.

All got hardening of the arteries, no matter what their lifestyle. In fact, the hunter-gatherers of the Aleutian Islands had the highest prevalence, with 60% of their mummies having evidence of atherosclerosis.

Food for thought.

Diseases of affluence and industrialization

Although atherosclerosis may be a common human experience no matter what, “diseases of affluence” (obesity, diabetes, and cardiovascular diseases) have certainly gone up dramatically in the past 50 years in industrialized countries like the U.S., especially compared to non-industrialized populations.

Over the last century — a period that is undoubtedly far too short for significant genetic adaptation — industrialization and technology have radically changed the way we eat and live.

Today, the average American subsists on foods that are packaged and commercially prepared. Rich in refined sugars and starches, highly processed fats, and sodium, these foods are designed to be so delicious that they run roughshod over the body’s normal fullness signals, and encourage overeating.

Consider: The top six calorie sources in the U.S. diet today are grain-based desserts (cake, cookies, etc.), yeast breads, chicken-based dishes (and you know that doesn’t mean roast chicken), sweetened beverages, pizza, and alcoholic drinks.

These are not ancestral foods. Nor foods that any nutrition expert, regardless of dietary persuasion, would ever recommend.

So when proponents of the Paleo diet claim that our modern Western diet isn’t healthy for us, they are absolutely correct.


But is the Paleo diet really Paleo?

Remember: There’s no single “Paleo diet”.

Our ancestors lived pretty much all over the world, in incredibly diverse environments, eating incredibly diverse diets.

Still, in most cases, primal diets certainly included more vegetables and fruits than most people eat today. So if we want to be healthier, we should do what our ancestors did and eat a lot of those. Correct?

Maybe so… but not necessarily for the reasons that Paleo proponents recommend.

First of all, most modern fruits and vegetables are not like the ones our ancestors ate.

Early fruits and vegetables were often bitter, much smaller, tougher to harvest, and sometimes even toxic.

Over time, we’ve bred plants with the most preferable and enticing traits — the biggest fruits, prettiest colors, sweetest flesh, fewest natural toxins, and largest yields.

We’ve also diversified plant types — creating new cultivars from common origins (such as hundreds of cultivars of potatoes or tomatoes from a few ancestral varieties).

Likewise, most modern animal foods aren’t the same either.

Beef steak (even if grass-fed) is not the same as bison steak or deer meat. And so on.

This doesn’t make modern produce or modern meat inherently good or bad. It’s just different from nearly anything available in Paleolithic times.

So the claim that we should eat a diet rich in vegetables, fruits, and meats because we are evolved to eat precisely those foods is a little bit suspect. The ones we eat today didn’t even exist in Paleolithic times!

Grains and grasses

Proponents of the Paleo diet argue that our ancestors’ diets could not have included a lot of grains, legumes, or dairy foods. And they contend that the past 10,000 years of agriculture isn’t enough time to adapt to these “new” foods.

This argument is compelling but doesn’t stand up to scrutiny.

  • To begin with, recent studies in the Proceedings of the National Academy of Sciences, using more advanced analytical methods, have discovered that ancient humans may have begun eating grasses and cereals before the Paleolithic era even began — up to three or even four million years ago!
  • Further research has revealed granules of grains and cereal grasses on stone stools starting at least 105,000 years ago.
  • Meanwhile, grain granules on grinding tools from all over the world suggest that Paleolithic humans made a widespread practice of turning grains into flour as long as 30,000 years ago.

In other words, the idea that Paleolithic humans never ate grains and cereals appears to be a bit of an exaggeration.

Are beans really bad for you?

Grains are not the only plant type that the Paleo diet typically limits. Advocates also recommend that you avoid legumes (beans, peanuts, peas, lentils) — and for a similar reason.

However, the idea that legumes were not widely available or widely consumed in Paleolithic times — like the argument that humans didn’t eat grains in the Paleolithic era — is false.

In fact, a 2009 review revealed that not only did our Paleolithic ancestors eat legumes, these were actually an important part of their diet! (Even our primate cousins, including chimpanzees, got into the bean-eating act.)

Legumes have been found at Paleolithic sites all over the world, and in some cases were determined to be the dominant type of plant food available. In fact, the evidence for wild legume consumption by Paleolithic humans is as strong as it is for any plant food.

What about anti-nutrients?

Okay. Maybe our ancient ancestors did eat a little bit of grain and some legumes — so the argument from history doesn’t really hold.

But Paleo proponents also offer another reason to avoid these foods: Their high concentration of anti-nutrients, which supposedly reduces their nutritional value to zilch.

There’s just one problem with this argument. It’s wrong.

Indeed, research suggests that the benefits of legumes far outweigh their anti-nutrient content, especially in light of the fact that cooking eliminates most anti-nutrient effects.

Lectins and protease inhibitors, in particular, are greatly reduced with cooking. And once cooked, these chemicals may actually be good for us. Lectins may reduce tumor growth, while protease inhibitors become anti-inflammatory and anti-carcinogenic.

Phytic acid

But what about phytate?

Grains, nuts, and legumes are rich sources of this anti-nutrient, which can bind to minerals such as zinc and iron and prevent their absorption. Surely that, in itself, is enough reason to avoid grains and legumes?

Not necessarily.

While phytic acid can be toxic if we eat too much of it, in more reasonable amounts it actually offers benefits.

For example, it can:

  •      have antioxidant activity
  •      protect DNA from damage
  •      be prebiotic (i.e. bacteria food)
  •      have anti-cancer properties
  •      reduce bioavailability of heavy metals like cadmium and lead.

And, in a mixed diet composed of other nutrient-dense whole foods, phytic acid is unlikely to cause problems.

In fact, nearly all foods contain anti-nutrients as well as nutrients — particularly plant foods.

For example, incredibly healthy foods such as spinach, Swiss chard, many berries, and dark chocolate are also sources of oxalate, an anti-nutrient that inhibits calcium absorption.

Green tea and red wine contain tannins, another anti-nutrient that inhibits zinc and iron absorption.

And so on.

Overall, phytic acid and other so-called anti-nutrients probably have a “sweet spot” (just like most nutrients).

  • Eating none or a small amount might be inconsequential.
  • Eating a moderate amount might be good.
  • Eating too much will hurt you. (See All About Phytates for more.)

Grains and inflammation

Another argument for a Paleo diet is that eating grains can lead to inflammation and related health problems.

While this can be true for people with celiac disease (about 1% of the population) and for those with non-celiac gluten sensitivity (estimated to be about 10% of the population, if it even truly exists), on the whole, the research does not support this argument any more than it supports the argument about anti-nutrients.

In fact, observational research has suggested that:

  • whole grains may decrease inflammation, but
  • refined grains may increase inflammation.

In other words, it appears that processing may cause problems, not the grain itself.

Meanwhile, controlled trials consistently show that eating grains, whether whole or refined, does not affect inflammation at all!

What can we make of that?

At worst, whole grains appear to be neutral when it comes to inflammation. (See All About Grains and A grain of truth for more.)

And overall, a substantial body of evidence from both observational and controlled trial research suggests that eating whole grains and legumes improves our health, including:

  •      improved blood lipids;
  •      better blood glucose control;
  •      less inflammation; and
  •      lower risk of stroke and coronary heart disease.

Eliminating these important foods from our diet to conform to anybody’s dietary ideology is probably a poor idea.

Evolution of the human GI tract

In Paleo circles, it’s sometimes said that while the world has changed in innumerable ways in the last 10,000 years, our genes have changed very little. And further, that we really only thrive in a world with similar conditions to the Paleolithic era.

Quite frankly, this is not how evolution or genetic expression works.

If humans could thrive only in an environment similar to or the same as the ones their ancestors lived in, our species would not have lasted very long.

Examples of the ways we have evolved in the past 10,000 years abound.

For example, over the past 8,000 years or so, about forty per cent of us have developed the capacity to consume dairy for a lifetime. As a species, we’re evolving a mutation whereby we continue to produce the lactase enzyme to break down lactose for far longer periods than our ancestors ever could. True, not everyone can digest lactose well, but more of us can do so than ever before.

And studies have shown that even people who don’t digest lactose well are capable of consuming moderate amounts of dairy, tolerating an average 12 grams of lactose at a time (the amount of lactose in one cup of milk) with few to no symptoms.

Additionally, the emerging science of epigenetics is showing that a “blueprint” alone isn’t enough — genes can be “switched off” or “on” by a variety of physiological and environmental cues.

Gut knowledge

Our digestive systems have adapted over millennia to process a low-energy, nutrient-poor, and presumably high-fiber diet. Meanwhile, Western diets have become high-energy, low-fiber, and high-fat.

Our genes produce only the enzymes necessary to break down starch, simple sugars, most proteins, and fats. They aren’t well adapted to cope with a steady influx of chicken nuggets, Tater Tots, and ice cream.

So how is it that we can still digest our food, albeit imperfectly at times?

Thank the trillions of bacteria that live in our gut. These friendly critters interact with our food in many ways, helping us break down tough plant fibers, releasing bound phytonutrients and anti-oxidants, and assisting us to assimilate many important compounds.

Now, we don’t have direct evidence of which bacterial species thrived in Paleolithic intestines, but we can be pretty confident that our ancestors’ microbial communities would not exactly match our own.

That’s because bacteria evolve and adapt at a rate much faster than our slow human genes. And for us, that’s a good thing.

It helps to explain why, even if the ancient human diet didn’t include grains, legumes, dairy, and other relatively modern agricultural products, we still might thrive on such a diet today – at least, with a little help from our bacterial friends.

The magical microbiome

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.

In fact, the total genetic makeup of these little creatures is at least 100 times greater than our own! (Essentially, we’re only 1% human. Think about that.)

This vast genetic diversity ensures that our GI tracts can adapt rapidly to changes in diet and lifestyle.

A single meal can change the type of bacteria that populate your gut. And as little as several days on a new diet can lead to dramatic changes in the bacterial populations in your GI tract.

The diverse, complex, and dynamic nature of our microbiome helps to explain why some of us seem to do well on one type of diet, while others will feel and perform better with another type of diet — even though, genetically, we’re all 99% the same!

Many of us can break down the more “modern” food compounds that Paleo advocates claim we do not tolerate well — simply because our intestines harbor bacteria that have evolved to do that job.

For instance, some Japanese people host unique bacteria that can help them digest seaweed.

And many people can alleviate symptoms of lactose intolerance by eating yogurt or other probiotic-rich foods that provide lactose-digesting bacteria.

So even if you don’t naturally break down lactose well, it’s possible, through the right combination of foods and/or probiotic supplements, to persuade the bacteria in your gut to do this job on your behalf.

What’s more, the same strategy could also address gluten intolerance. Recent research shows that some bacteria actually produce enzymes that break down gluten — as well as phytic acid — reducing any inflammatory or anti-nutrient effects.

Which, as we know, are two of the main reasons people recommend starting Paleo diets in the first place.

Modern Paleo research

No matter how you slice it, the Paleo proponents’ evolutionary arguments just don’t hold up.

But that doesn’t mean that the diet itself is necessarily bad.

Maybe it’s a good diet for completely different reasons than they say.

To find out if that is so, a number of researchers have been putting Paleo diets to the test with controlled clinical trials. And so far, the results are promising, though incomplete.

Paleo vs. Mediterranean diets

Perhaps the best known of these researchers is Dr. Lindeberg — the one who also studied the Kitavan Islanders. He and his colleagues have conducted two clinical trials testing the efficacy of the Paleo diet.

In the first, they recruited diabetic and pre-diabetic volunteers with heart disease and placed them on one of two diets:

  1. A “Paleolithic” diet focused on lean meat, fish, fruit, vegetables, starchy root vegetables, eggs, and nuts, or
  2. A “Mediterranean” diet focused on whole grains, low-fat dairy, vegetables, fruit, fish, oils, and margarine.

After 12 weeks, the Mediterranean group lost body fat and saw an improvement in markers of diabetes. Four of the nine participants with diabetic blood sugar levels at the beginning of the study had normal levels by the end. That’s a very good result and must have made the participants happy.

But those in the Paleo group fared even better.

They lost 70 percent more body fat than the Mediterranean group and also normalized their blood sugars. In fact, all ten participants with diabetic blood sugar levels at the beginning of the study reached non-diabetic levels by the end of the study.

By any estimation, that is an astonishing result.

Now, these volunteers were suffering from mild, early cases of diabetes. But a second study of long-term diabetics showed that a Paleo diet didn’t cure them but it did improve their condition significantly.

Other research has found:

  • The Paleo diet is more satiating per calorie than a Mediterranean diet.
  • The Paleo diet improves blood pressure, glucose tolerance, and blood lipids.

However, one caveat: Like most low-carb trials, the macronutrients (especially protein) in these studies weren’t matched.

The Paleo group ate a lot more protein, compared to the other diet groups. Plenty of protein helps keep our lean mass dense and strong, stay lean, and feel satisfied by our meals.

So, we’re not just comparing apples to oranges when protein intakes are different; this is more like comparing grains to goat meat. Literally.

The Paleo diet may indeed be the best plan, but it’s hard to know for sure without direct comparisons that match macronutrients and calories.

Conclusion & recommendations

What does the Paleo diet get right?

Despite the faulty evolutionary theory it’s based on, in the end, the Paleo diet likely gets more right than it gets wrong.

  • Paleo-style eating emphasizes whole foods, lean proteins, vegetables, fruits, nuts, seeds, and other healthy fats, which is a massive improvement over the average Western diet.
  • Paleo-style eating has been extremely effective for improving several chronic diseases. That alone is a huge plus.
  • Paleo-style eating has made us more aware of how processed and crappy a lot of our 21st century food is.

However, we need more rigorous (and carefully matched) trials before we can reach any definitive conclusions.

What are the challenges?

Despite its obvious benefits over the typical Western diet, the Paleo diet has some flaws.

  • The evidence for excluding dairy, legumes, and grains isn’t (yet) strong. So as a nutrition coach, I can’t say it’s a one-size-fits-all prescription. Certainly, some people should avoid dairy and gluten, and keep legume and grain consumption more modest. But most of us can improve the way we look, feel, and perform without completely eliminating these foods.
  • The evolutionary arguments don’t hold up. The human species isn’t simply a collection of adaptations to life in the Paleolithic era. We are an ever-evolving accumulation of inherited characteristics (and microorganisms) that have been switched, reconstructed, lost, and reclaimed since the first prokaryotes came to life on Earth. This evolution has continued over the past 10,000 years — and won’t stop any time soon.
  • In the broader sense, strictly following a list of “good” and “bad” or “allowed” and “not allowed” foods tends to be problematic for most people. Generally, this approach leads to anxiety and all-or-nothing thinking. Maybe it makes us feel more confident and (falsely) sure of ourselves in the short term. But it’s less effective over the long-term — because ultimately, it decreases our consistency.

This may explain why we are seeing the Paleo diet itself evolve.

It’s evolution, baby

Many Paleo advocates have recently come to appreciate and encourage the addition of moderate amounts of starch (albeit a more limited variety of options than I would prefer), as well as some dark chocolate, red wine and non-grain spirits (such as tequila), and grass-fed dairy.

These additions make life much more pleasant. They make healthy eating more attractive and achievable.

In fact, this new “leniency” may partly explain why the Paleo diet continues to gain traction in mainstream nutrition circles.

Because in the end, moderation, sanity and your personal preferences are more important than any specific food list, anti-nutrient avoidance, or evolutionary theory.

What to do today

Consider the good things about ancestral lifestyles. This includes fresh food, fresh air, lots of movement, good sleep, and a strong social network. How could you get just a little bit of these in your life today?

Think about how you could move along the spectrum — from processed 21st century life and food — to choices that are a little more in tune with what your ancient body needs and loves.

Learn a little more about your ancestors. Evolution is cool. Dig into your roots: Where did your people come from? What were their ancestral diets? (23AndMe will tell you how much of your DNA is Neanderthal.)

Keep it simple and sane. Doing a few good things pretty well (like getting a little extra sleep or fresh veggies) is much better than trying to get a lot of things “perfect”.

Stay critical and informed. Avoid dogmatic or cultish thinking. Be skeptical. Look for evidence. Question everything. Primal eating is a super cool idea and may turn out to be more or less right; just keep your late-evolving prefrontal cortex (aka your thinky brain) in the game as you consider all the options.

Help your old body (and your trillions of little buddies) do their jobs. Our bodies are resilient. We didn’t get to be one of the dominant species on the planet by being fussy, delicate flowers. Nevertheless, think about how you can nourish your body optimally in order to give your body and microbiome the best chance of surviving and thriving.

Eat, move, and live… better.

Yep, we know… the health and fitness world can sometimes be a confusing place. But it doesn’t have to be.

Let us help you make sense of it all with this free special report.

In it you’ll learn the best eating, exercise, and lifestyle strategies – unique and personal – for you.

Click here to download the special report, for free.


Click here to view the information sources referenced in this article.