Just what is the Paleo diet?


It seems that every month a new fad diet comes along. Some involve eating one specific food over another and shaping a diet plan for your lifestyle, while others focus on total body health. Some are designed to help a person lose weight, others designed to build muscle or provide the most energy. Some diets are even designed to help boost a man's testosterone to maximize sex drive.

One of the more popular diets in recent years has been the Paleo diet. I spoke with Mathieu Lalonde to clarify what the diet entails and who might benefit from following it. Lalonde holds a PhD in organic chemistry from Harvard University and has been constructively criticizing the Paleo diet for some time.

What is the Paleo diet?

“Simply put, eating Paleo means following a diet where grains, legumes, and dairy are not consumed. The Paleo diet seeks to emulate the way our Paleolithic ancestors ate using modern foods, such as meats, seafood, fruits, vegetables, roots, tubers, nuts and seeds.”

So this diet focuses primarily on consuming meat…?

“There are quite a few misconceptions surrounding the diet and many have been borne out of attempts to discredit or marginalize the lifestyle. The diet is often criticized for its heavy focus on animal products. Although meat is allowed and often mentioned first, there is no focus on meat in the diet per se. In fact, vegetarians can follow the lifestyle as long as their diets are grain-, legume- and dairy-free. Along the same lines, the Paleo diet is often vilified because it allows for heavy consumption of red meat. However, red meat does not need to be consumed. Someone could easily pull off a Paleo diet with white meat and seafood, while excluding all red meat.”

Is it a low-carb diet?

“The Paleo diet is often considered to be a low-carb regimen. I don’t know where this comes from. There is no macronutrient ration that comes with the paleo prescription, only a list of allowed foods. Both high- and low-carb diets are feasible with these foods. High-carb would focus on tubers (such as potatoes) and fruit while low-carb would focus on meat, seafood, and fatty fruits like avocado, coconut, and olives.”

So why do you think the Paleo diet works?

“I offer four reasons. First, the Paleo diet limits junk food. Let’s face it, there simply aren’t a lot of highly palatable and rewarding refined foods that can be consumed when grains, legumes, and dairy aren’t on the menu. Cakes, doughnuts, ice cream…goneOur ancestors sought sugar, salt and fat because it offered a survival advantage in an environment where food was scarce. They would eat a lot of sugar, salt or fat contained in food when it was available in order to put on a few pounds that would help them survive when food was not available in large quantities. Unfortunately, modern humans still seek out sugar, salt and fat, even though food is readily available all year round. Junk food companies take full advantage of this behavior by designing foods that contain the perfect combination of sugar, salt and fat, which makes the foods irresistible and addictive. People tend to overeat junk food as a result and gain weight. I recommend reading the book “Sugar, Salt, Fat” as well as the blog “Whole Health Source” for more information on the addictive nature of highly palatable/rewarding foods.

Some candy and potato chips would still be available on the Paleo diet, although many Paleo eaters eschew nightshades (i.e. they don’t eat potatoes, tomatoes, eggplants, and peppers)

Second, the Paleo diet focuses on foods with high nutrient density. Contrary to what you may have heard, grains and legumes aren’t that nutritious. At least not when compared to those eaten on the Paleo diet. Grains and legumes are thought to be nutritious because they contain a decent amount of vitamins and minerals in their raw state. However, grains and most legumes are not edible in their raw state. When one looks at the nutrient density of grains and legumes after cooking, it simply does not compare. As you can imagine, improving the nutrient content of the diet typically improves health.

Next, Paleo dieters avoid many allergenic and immunogenic proteins. Legumes, grains and dairy contain very allergenic and immunogenic proteins. Wheat, soy, peanuts (which is a legume), and milk are very common allergens. Grains in particular contain immunogenic proteins, called prolamines, that trigger immune responses and increase inflammation. Gluten, which is a protein composed of gliadin and glutenin, is the best studied of all the prolamines. The number of diseases in which gluten is implicated keeps growing by the day and includes: celiac, type 1 diabetes, multiple sclerosis, dermatitis herpetiformis, arthritis, headaches, various neuropathies, psychosis, and schizophrenia. I don’t see why grains and legumes should be consumed when they are not nutrient dens and contain so many problematic proteins.

Eggs are the only common allergens that remain on a Paleo diet. Some people are sensitive to nightshades but I wouldn’t call them common allergens.

Finally, the foods consumed on this diet are sustainable. Grain agriculture is simply not sustainable as currently practiced, as it leads to massive soil erosion and desertification. Also, the way people are raising animals in confined animal feeding operations is also not sustainable. However, there is a sustainable alternative: raising livestock on pasture with proper rotation.”

Is this diet recommended for the general population? What type of person should try the Paleo diet?

“Anybody, really, can try this approach. If you're looking for better health, improved athletic performance, weight loss, or have a quirky health issue that nothing can fix – give the Paleo diet a try. You can't lose in my opinion.”

How is this diet different from other diets? What separates it from other "fad" diets?

“The main thing is that it works long term. It works not just for losing weight, but for reversing certain autoimmune diseases as well. A lot of people have reported that some weird disease they did not understand and couldn’t get rid of somehow disappeared on a Paleo diet. I really hope that the Paleo diet gets more attention from the public and from scientists in the future.”

You mentioned that you are a scientist by trade. How has that changed the way you approach nutrition?

“Learning the scientific method, and how to apply it, changed my nutrition. I was a vegan for two years and a vegetarian for eight years. When I finished my PhD in organic chemistry, I decided to analyze my diet with the rigor of a core science. I was not pleased to realize that any of the things I believed to be true were misinterpreted data or merely correlations from weak, and often times poorly conducted, observational studies. From a scientific standpoint, nutrition should be is a subfield of biology or biochemistry. However, many of the studies are done from the context of public health and I can’t say that they are the quality standards of scientific studies. I see a lot of personal biases and cherry-picking of data getting in the way of real science and real answers when it comes to nutrition. In science, you're not trying to prove yourself right; instead, you're trying to find the right answer. That can often mean proving yourself wrong.

I see a lot of people searching the literature while selectively picking only papers that agree with the answer they think is right. That’s not science. In fact, many scientists look for evidence that would prove them wrong. The type of research that is currently done in the field of nutrition needs to rise to a higher standard if we have any hope of helping our ailing population.

You express some skepticism about the theories supporting the diet.

Indeed I do! Let’s go over some of the typical arguments that are put forth to justify the diet.

  1. Our Paleolithic ancestors and modern hunter-gatherers consumed a diet mostly devoid of grain, legumes, and dairy and suffered from none of the diseases of civilization. Hence, eating a diet devoid of grains, legumes and dairy will allow us to avoid the diseases of civilization.

  2. Our Paleo ancestors evolved over millions of years without consuming foods that became available only after the advent of agriculture; hence, we are not adapted to these evolutionary novel foods.

  1. Our genes are virtually identical to those of our Paleolithic ancestors; hence, we are best adapted to the environment they lived in and food they consumed.

Let’s look at #1 first. The problem with this argument is that it uses an observation to establish cause and effect. Observations only establish correlation, never cause and effect.

Correlations are very useful for generating hypotheses. In the case of Paleo, one could hypothesize that consuming the diet of our ancestors would allow us to avoid diseases of civilization given that there is a correlation.

The nutrition of our ancestors simply cannot be the only factor that explains their lack of diseases of civilization. Our ancestors lived in different environments, had different stresses in their lives, had more time to sleep, and faced less pollution. These are things we would refer to as confounding factors, which correlate to the dependent and independent variables. The presence of confounding factors is another reason why correlation should never be assumed to establish a causal relationship.

Now let’s look at argument #2. The assumption here is that a species is not adapted to a food because it was not previously consumed by that species. This is absolutely false. There are plenty of examples, including our ancestors, of species adopting evolutionary novel sources of food and thriving on them. Let’s not forget that food is an important driver of evolution and adaptation. Our ancestors began by eating mostly fruit, then they scavenged brain and marrow from carcasses, then they started hunting animals and digging for tubers. During this time, our ancestors discovered cooking and created tools. The guts of our ancestors shrank, because they were consuming foods that were increasingly easier to digest (both due to the nature of the food and to cooking), while their brains grew as a result of the increased nutrient density of their new diet. All of this happened with food our ancestors never consumed before.

Argument #2 also assumes that human beings could not possibly have discovered a better source of food after the advent of agriculture. I’ll admit that our track record is pretty poor when it comes to new foods but the assumption is still ridiculous. I’d argue that dairy was a good addition to our food supply, albeit not for everyone (casein and lactose intolerance are fairly common).

Now let’s look at argument #3. This has to be the most damning statement of them all. Here is a group of people that claims to take an evolutionary approach to life but the statement shows that supporters of the Paleo diet do not understand evolution. Human beings and chimps have virtually identical genomes. Does this mean we should be eating like chimps? Of course not! The difference between the species lies in the epigenome (i.e. gene expression). You see, it’s not just the genes that matter, how each gene is expressed is equally, if not more, important. One of the mechanisms through which adaptations arise is change in gene expression (i.e. epigenetic changes), where certain genes are turned off while others are turned on. Just because two species have similar genes does not mean that they are identical or that they will both thrive in similar environments or with similar foods. Nothing could be further from the truth. Now I know what you are thinking, maybe the epigenome of modern humans and our Paleolithic ancestors are similar? That is highly unlikely given the substantial differences (environment and food) in which they evolved. Nevertheless, it is absurd to suggest that we should be eating like species that have similar genomes. Just because our genes are virtually identical to that of our Paleolithic ancestors does not mean we should eat the same way. There have been adaptations since the dawn of agriculture. Lactase persistence is a good example.

Now let me tell you a story. When I started my graduate studies, the guy sitting next to me had just published this awesome paper in a very prestigious journal. The paper described an enantioselective reaction that was catalyzed by a simple chiral molecule. The data that was available at the time pointed toward a particular mechanism of action. The student who did the work defended his thesis and passed with flying colors, eventually landing a job in industry. Another graduate student, who joined the lab later on, decided to do some kinetics on the reaction and discovered that another mechanism, one that was completely compatible with the previous data, was operating. This means that the interpretation of the data in the previous researchers thesis was wrong and that another mechanism was operating. Nevertheless, this did not change the fact that the reaction worked as published. That is, if someone followed the published procedure they would get exactly the same result that we did in our lab. Even if the mechanism used to explain the reaction is incorrect, the reaction still works. I think this is what is going on with Paleo. The explanation is not quite right but it does not change the fact that the diet still works. These types of things happen in science all the time. I understand the issue and I’ve been trying to work with the Paleo community to get them to recognize their mistakes. For some reason, this is easier to do with science than with diet. ”