Is The Paleo Diet Based On A Myth?

Are Starchy Foods Bad For Us? 

Author: Dr. Stephen Chaney

the paleo dietThe Paleo Diet is still very popular. And it does have its good points. It is a whole food diet. It eliminates sodas, junk foods, and highly processed foods. Any diet that does that can’t be all bad.

But is it unnecessarily restrictive? It eliminates starchy foods like grains, beans, peas, and corn. It is true that widespread consumption of these foods did not occur until after the agricultural revolution some 12,000 years ago. Our paleolithic ancestors probably did not consume significant quantities of these foods.

But did they consume other starchy foods? Our ideas about this have come primarily from comparing the diets of modern man with the diets of the few primitive hunter-gatherer populations that currently exist in our world. Based on that comparison, some Paleo advocates have concluded that the paleolithic diet contained few, if any, starchy foods.

More importantly, some Paleo advocates have gone a step further to assert that our bodies are not designed to eat starchy foods. They claim that foods like grains, legumes, corn, and potatoes are bad for us. They should be avoided.

How can we test whether these claims are true? After all, we don’t have any way of directly determining whether our paleolithic ancestors ate starchy foods or not. Or do we? That question is the topic of a new study (JA Fellows et al, PNAS, 118 No. 20 e2021655118 I will share with you today.

But first I need to acquaint you with what starch is and how we digest it. Once again, it is time for Biochemistry 101.

Biochemistry 101

professor owlStarch is simply a long polymer of glucose molecules. Digestion of starch starts in our mouth. Our saliva contains an enzyme called alpha-amylase that breaks the bond between adjacent glucose molecules. Alpha-amylase breaks starch down sequentially, first to maltodextrin (a shorter polymer of glucose molecules), then to maltose (two glucose molecules), and finally to glucose.

[Note: The nutrition gurus that tell you to read labels and avoid foods with maltodextrin are ignoring the fact that we produce maltodextrin naturally whenever we digest starch in the foods we eat.]

All humans contain the alpha-amylase gene. Simply put, that means that all humans have the potential to digest starchy foods.

However, not all humans have the same number of copies of the alpha-amylase gene. When we habitually consume a diet containing starchy foods, our bodies duplicate the alpha-amylase gene until our saliva contains enough alpha-amylase to easily digest the amount of starchy foods we are consuming. Simply put, that means our bodies are designed to easily adapt to the amount of starchy foods in our diet.

Most modern human populations have between six and 30 copies of the alpha-amylase gene. Our saliva contains a lot of alpha-amylase. However, the few primitive hunter-gatherer societies that still exist in our world have only two or three copies of the alpha-amylase gene. Their saliva contains very little alpha-amylase.

It is this difference that has led to the hypothesis that our paleolithic ancestors did not possess salivary alpha-amylase, which implies they didn’t eat starchy foods. This hypothesis also assumes that humans only began producing significant quantities of salivary alpha-amylase after the agricultural revolution when starchy foods like grains, rice, and beans became widely available.

This hypothesis is one of the central tenets of the Paleo diet. But we need to remember that it is just a hypothesis. It has not been directly tested because we thought there was no way to determine the starch content of the paleolithic diet – until now. However, before we get to the study that explodes this hypothesis, I want to revisit the Paleo Diet myths I described in an earlier issue of “Health Tips From The Professor”. I call this next section “Unicorns And The Paleo Diet”.

Unicorns And the Paleo Diet

the paleo diet and unicornsI titled this section “Unicorns and the Paleo Diet” because both are myths. In fact, the Paleo Diet is based on several myths.

Myth #1: Our ancestors all had the same diet. What we currently know as the Paleo diet is based on the diets of a few primitive hunter-gatherer societies that still exist in some regions of the world. However, when you look at the data more carefully, you discover that the diet of primitive societies varies with their local ecosystems.

The “Paleo diet” is typical of ecosystems in which game is plentiful and fruits and vegetables are less abundant or are seasonal. In ecosystems where fruits and vegetables are abundant, primitive societies tend to be more gatherers than hunters. They eat more fruits and vegetables and less meat.

The assumption that starchy foods were absent in the paleolithic diet is also a myth. For some primitive societies, starchy fruits or starchy roots are a big part of their diet. In short, our paleolithic ancestors ate whatever nature provided.

Myth #2: Our genetic makeup is hardwired around the “paleolithic diet”. In fact, humans are very adaptable. We are omnivores, which means we can eat whatever nature provides. We are designed to thrive in a wide variety of ecosystems. It is this adaptability that has allowed us to expand to every nook and cranny of the world.

For example, the enzymes needed to digest grains are all inducible, which means the body can turn them on when needed. Our paleolithic ancestors may not have eaten much grain, but we can very quickly adapt to the introduction of grains into our diet. As I described above, for alpha-amylase this adaptation occurs through gene duplication.

Myth #3: Our paleolithic ancestors were healthier than modern man: It some respects, the paleolithic diet is healthy, as I mentioned above. However, we need to remember that our paleolithic ancestors rarely lived past 30 or 40. They simply did not live long enough to experience degenerative diseases like heart disease and cancer. We have no idea whether a diet that served our paleolithic ancestors well will keep us healthy into our 70s, 80s and beyond.

How Was This Study Done?

Clinical StudyThis is a fascinating study, and one that would have been impossible just a few years ago. As I have described in previous issues of “Health Tips From the Professor”, studies on our microbiome, the bacteria that inhabit our bodies, is a rapidly evolving area of research.

When we talk about our microbiome, we generally think about our gut bacteria. However, the term “microbiome” includes all the bacteria that reside in our body, including those that reside in our oral mouth.

And, like our gut bacteria, the species of bacteria that reside in our mouth are heavily dependent on the foods we eat. Specifically, there are three species of oral bacteria that thrive on starch. They possess an “amylase binding protein” that allows them to capture salivary alpha-amylase and use it to break down dietary starch so they can use it as an energy source.

Consequently, the abundance of these three bacterial species in the oral microbiome is a precise marker for the amount of starch in a person’s diet. More importantly, high throughput DNA sequencing and supercomputers have made it simple to sequence all the bacteria in the oral microbiome and quantify the relative abundance of these three bacterial species.

You are probably thinking, “That’s fine, but how could you possibly determine the abundance of those bacteria in the mouth of a paleolithic human?” Here is where it gets really interesting!

The bacteria in our mouth form biofilms on our teeth, something we refer to as plaque. If the plaque remains on our teeth long enough, it calcifies, forming what is referred to as dental calculus (tooth tartar).

In the modern world we remove dental biofilms by brushing after every meal. We remove dental plaque and tartar by semi-annual visits to the dentist. But these are recent developments. They are not something our ancestors did.

Our ancestors simply accumulated dental calculus during their lifetime. More importantly, the dental calculus excluded air and water, so it preserved the DNA of the bacteria in their oral microbiome. That was the basis of the current study.

The study was a collaboration of 50 scientists over a 7-year period. The scientists sequenced 124 oral microbiomes from humanoid species in Africa, including Neanderthals (430,000 to 40,000 years ago), Late Pleistocene (129,000 to 11,700 years ago) humans, and modern-day humans.

Bacterial DNA from modern-day humans was obtained from dental calculus obtained during routine dental cleaning procedures by practicing dentists. The older DNA samples were obtained from dental calculus in the teeth of skeletal remains. The oldest DNA sample was obtained from a Neanderthal that lived around 100,000 years ago.

For comparison they also obtained bacterial DNA from the dental calculus of chimpanzees and gorillas, man’s closest primate relatives.

The species of bacteria in the oral microbiome from all these samples were determined by high throughput sequences and computerized analysis using high speed supercomputers.

Is The Paleo Diet Based On A Myth?

Question MarkThere were three important findings from this analysis:

  1. The species of bacteria in the oral microbiome of Neanderthals and Late Pleistocene humans was much more diverse than for modern humans. This suggests that their diets were more diverse (perhaps depending on what foods were available in their environment), while modern diets have become more standardized.

2) The species of bacteria that thrive on starchy foods were remarkably constant in the oral microbiome of all human species from Neanderthals to Late Pleistocene humans to modern-day humans.

3) The species of bacteria that thrive on starchy foods were virtually absent from the oral microbiomes of our most closely related primates – chimpanzees and gorillas.

The authors concluded, “This … supports an early importance of starch-rich foods in Homo evolution.”

In other words, our paleolithic ancestors likely did eat starchy foods. Their diet may not have contained grains, rice, or beans in significant quantities. However, they consumed whatever starchy roots, fruits, and vegetables they could find.

So, is the Paleo diet based on a myth? It depends on how you phrase the question.

  • If we ask whether our paleolithic ancestors consumed grains, rice, or beans, the answer is probably, “No”. The introduction of these foods in significant quantities probably depended on the agricultural revolution that occurred thousands of years later.
  • If we ask whether our paleolithic ancestors consumed starchy foods, the answer is probably, “Yes”. The foundation of the Paleo diet was based on a myth. Their oral microbiome contained bacterial species that thrived on starchy foods. In fact, starchy foods may have been an important staple in their diet because they are more calorie dense than other fruits and vegetables.
  • If we ask whether our paleolithic ancestors were capable of thriving on a diet that included grains, rice, and beans, the answer is also probably, “Yes”. The oral bacterial species that thrive on starchy foods do so by utilizing the alpha-amylase in human saliva. This means our paleolithic ancestors likely had enough alpha-amylase in their saliva to digest and to thrive on starchy foods like grains, rice, and beans.

Are Starchy Foods Bad For Us?

Starchy FoodsIt is not just the Paleo diet. Many popular diets have villainized starchy foods. Are starchy foods as bad for us as some “experts” would have you believe?

Let’s start by identifying starchy foods. If we think in terms of whole foods, they are:

  • Root vegetables (for example, potatoes, sweet potatoes, beets, carrots, and parsnips).
  • Legumes (for example, beans, peas, and lentils).
  • Grains (for example, wheat, rye, barley, oats, and rice).
  • Winter squash (for example, acorn squash, butternut squash, hubbard squash, and pumpkin).
  • Corn

These foods are good sources of nutrients and phytonutrients. Many of them are also excellent sources of fiber, including a special type of fiber called resistant starch. (I have described the benefits of resistant starch in a previous issue of “Health Tips From the Professor”.) These are foods that definitely deserve to be part of a healthy diet.

The only drawback of starchy vegetables is that they tend to be more calorie dense than other vegetables. While this was a “plus” for our paleolithic ancestors, it is not quite as advantageous in our modern world. If you are trying to watch your calories, my advice is to incorporate these foods into your diet sparingly.

However, there is another class of starchy foods you want to avoid. Of course, I am talking about highly processed foods made from grains, legumes, and corn. They retain all the calories but lose most of the nutrients, phytonutrients, and fiber of the foods they came from.

In short, starchy whole foods are a valuable part of a healthy diet. It is the starchy processed foods made from these whole foods you want to avoid. Of course, I am talking about bread, pasta, and pastries made from refined grains and sugar.

So, how do you know which starchy foods to avoid? My advice is not to become an expert label reader. Just eat foods without labels.

The Bottom Line

One of the founding principles on which the Paleo diet is based is that our paleolithic ancestors ate very few starchy foods, and the human body really isn’t designed to handle these foods. Accordingly, the Paleo diet recommends we should avoid starchy foods like grains and legumes. This has the unfortunate effect of creating an unbalanced diet that overemphasizes meat and animal fats.

But is this founding principle correct, or is it just a myth? When you look beneath the surface, you discover that it is a hypothesis based on the diets of the few primitive hunter-gatherer populations that still exist in our world.

It has been assumed that was as good an estimate of the paleolithic diet as we could get. After all there was no way to directly determine the starch content of the paleolithic diet – until now.

In this issue of “Health Tips From the Professor” I describe a novel approach that allowed scientists to determine the species of bacteria residing in the mouth of our humanoid ancestors based on the DNA extracted from the plaque coating their teeth. (For details on how this was done, read the article above.)

What the scientists found was that all human species, including a Neanderthal who died 100,000 years ago, harbored bacteria in their mouths that thrive on starchy foods.

The scientists concluded, “This … supports an early importance of starch-rich foods in Homo evolution.” In other words, our paleolithic ancestors likely did eat starchy foods. Restricting whole grains and legumes from the Paleo diet is based on a myth. They are an important part of a healthy diet.

For more details about the study and which starchy foods are bad for you, read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease.

Is The Paleo Diet Bad For Your Heart?

Is The Paleo Diet Bad For Your Gut?

the paleo dietThere is a lot to like about the Paleo diet:

·       It is a whole food diet. Any diet that eliminates sodas, junk foods, and highly processed foods is an improvement over the American diet.

·       It includes lots of vegetables and some fruits.

·       It helps you lose weight, and any diet that results in weight loss improves your blood work – things like cholesterol, triglycerides, blood sugar control and more.

However, there are concerns the Paleo diet may not be healthy long term.

·       In part, that is because the diet is high in meat, red meat, and saturated fat.

·       Equally important, however, is what the diet eliminates – namely whole grains, legumes (beans), and dairy.

Those of you who have read my book, “Slaying The Food Myths”, know that I say: “We have 5 food groups for a reason”. This is particularly true for the plant food groups. That’s because each plant food group provides a unique blend of:

·       Vitamins and minerals. Those can be replaced with good multivitamin/multimineral supplement.

·       Phytonutrients. You can only get the full complement of health-promoting phytonutrients from a variety of foods from all 5 food groups.

·       Fiber. There are many kinds of fiber and they each play different roles in our intestine. You can only get all the health-promoting varieties of fiber by consuming fruits, vegetables, whole grains and legumes.

·       Gut bacteria. What we call fiber, our gut bacteria call food. Each of the plant food groups supports different populations of friendly gut bacteria.

Based on this reasoning, one might suspect that the Paleo diet might alter our gut bacteria in ways that could be bad for our health. Until recently, this sort of reasoning was just a theoretical concern. That’s because:

1)    We knew far too little about the health effects of different populations of bacteria. This is rapidly changing. Several recent studies have systematically investigated the connection between gut bacteria and health outcomes.

2)    We knew our diet influenced the bacteria populations found in our gut, but we had no understanding of how these changes might influence our health. This too is changing. The study (A Genoni et al, European Journal of Nutrition, https://doi.org/10.1007/s00394-019-02036-y) I discuss this week is an excellent example of recent studies linking diet, gut bacteria, and risk factors for disease.

How Was The Study Done?

can you believe clinical studies doctorThis study recruited 91 participants from Australia and New Zealand. It was a very well designed study in that:

·       The Paleo diet group (44 participants) was recruited based on self-proclaimed adherence to the Paleo diet (< 1 serving/day of grains and dairy products) for one year or more. This is important because short term effects of switching to a new diet are confounded by weight loss and other factors.

o   After analyzing the diets of the Paleo group, the investigators found it necessary to subdivide the group into Strict Paleo (< 1 serving/day of grains and dairy products) and Pseudo-Paleo (> 1 serving/day of grains and dairy).

·       The control group (47 participants) was recruited based on self-proclaimed adherence to a “healthy diet” for 1 year or more with no change in body weight (A healthy diet was defined as a whole food diet containing a variety of foods from all 5 food groups). This is important because far too many studies compare the diet they are promoting to an unhealthy diet with a lot of sugar and highly processed junk foods. These studies provide little useful information because almost anything is better than an unhealthy diet.

·       The participants completed a diet survey based on the frequency of consumption of various foods during the previous year. However, because diet surveys based on the recollection of participants can be inaccurate, the investigators used two rigorous tests to validate the accuracy of those diet surveys.

o   The first was a 3-day weighed dietary record (WDR). Simply put, this means that participants weighed and recorded all foods and beverages before they were eaten for 3 days. Two of those days were weekdays, and one was a weekend day.

o   Secondly, the investigators used blood, urine, and metabolic measures to independently determine protein and energy intake of each participant. Participants who were identified by these means as under reporting both protein and energy were considered unreliable dietary reporters and were excluded from the analysis.

o   It is very rare to find a study that goes to this length to validate the accuracy of the dietary data used in their analysis.

The participants also provided blood, urine and stool samples and completed a physical activity assessment.

What Were The Differences Between The Paleo Diet And The Healthy Control Diet?

Paleo FoodsOnly the Strict Paleo Diet group was faithfully following the Paleo diet. In addition, most of the results with the Pseudo Paleo Diet Group were intermediate between the other two diets. Therefore, to simplify my discussion of this study I will only compare the Strict Paleo Diet group, which I refer to as the Paleo Diet group, with the Healthy Diet control group.

The Paleo diet emphasizes fresh vegetables, especially green leafy vegetables, and discourages grains. Thus, it is no surprise that:

·       The Paleo Diet group ate 74% more vegetables and 3 times more leafy green vegetables than the Healthy Diet group.

·       The Paleo Diet group ate only 3% of the grains and 3% of the whole grains compared to the Healthy Diet group.

The Paleo diet encourages consumption of meat and eggs and discourages consumption of dairy and plant proteins. Thus, it is not surprising that:

·       The Paleo Diet group ate 3 times more red meat and 5 times more eggs than the Healthy Diet group.

·       The Paleo Diet group ate 10% of dairy foods compared to the Healthy Diet group.

·       The Paleo Diet group consumed two times more saturated fat and cholesterol than the Healthy Diet group.

The most interesting comparison between the two diets was the following:

·       Intake of total fiber, insoluble fiber, and soluble fiber was comparable on the two diets.

·       However, intake of resistant starch was 50% lower in the Paleo Diet group. This is significant because:

o   Resistant starch is a type of fiber found primarily in whole grains, legumes, potatoes, and yams (Potatoes and yams are also dietary “no nos” on most low-carb diets).

o   Resistant starch is an especially good food for certain species of healthy gut bacteria.

Is The Paleo Diet Bad For Your Gut?

Bas BacteriaBecause resistant starch affects gut bacteria, the study next looked at the effect of the two diets on the populations of gut bacteria. This is where the story starts to get interesting. When they looked at different groups of gut bacteria, they discovered that:

·       Bifidobacteria were much more abundant in the Healthy Diet group than in the Paleo Diet group, and the amount of Bifidobacteria in the gut was directly proportional to the amount of whole grains in the diet.

o   This is important because previous studies have suggested Bifidobacteria help maintain intestinal barrier integrity and protect against irritable bowel syndrome and obesity.

·       Roseburia were also much more abundant in the Healthy Diet group and proportional to the amount of whole grains in the diet.

o   This is important because previous studies have suggested Roseburia protect against inflammatory bowel diseases like Crohn’s disease and ulcerative colitis.

·       Hungatella were much more abundant in the Paleo Diet group and were inversely proportional to the amount of whole grains in the diet.

o   This is important because Hungatella metabolize carnitine and choline, which are found in meats (especially red meats), egg yolks, and high fat dairy, into a compound called trimethylamine or TMA. TMA is then further metabolized in the liver to trimethylamine-N-oxide, or TMAO.

o   TMAO is a bad player. It is positively associated with heart disease, stroke, kidney disease, diabetes, and Alzheimer’s disease. However, the evidence is strongest for heart disease. TMAO has been called an independent risk factor for cardiovascular death.

Because of this, the study looked at TMAO levels in the blood of the two diet groups. These results were concerning:

·       TMAO levels were 2.5-fold higher in the Paleo Diet group than in the Healthy Diet group.

·       As might be expected, TMAO levels were positively correlated with red meat intake and inversely proportional to whole grain intake.

Is The Paleo Diet Bad For Your Heart?

heart diseaseWhen you put all the evidence together you have a compelling argument that the Paleo diet is likely to increase the risk of heart disease. Let me summarize the data briefly:

1)    The Paleo diet discourages the consumption of whole grains.

2)    Whole grains are a major source of a dietary fiber called resistant starch.

3)    Because the Paleo diet is low in resistant starch, it causes a decrease in two healthy types of gut bacteria and an increase in a type of gut bacteria called Hungatella.

4)    Hungatella metabolize compounds found in meat, eggs, and dairy to a precursor of a chemical called TMAO. This study showed that TMAO levels were 2.4-fold higher in people consuming a Paleo diet.

5)    TMAO is associated with coronary artery disease and is considered an independent risk factor for cardiovascular death.

The authors of the study concluded: “Although the Paleo diet is promoted for improved gut health, results indicate long-term adherence is associated with different gut microbiota and increased TMAO. A variety of fiber components, including whole grain sources, may be required to maintain gut and cardiovascular health.”

Of course, studies like this are looking at associations. They are not definitive. What we need are long term studies looking at the effect of the Paleo diet on heart disease outcomes like heart attack and stroke. Until we have these studies my advice is:

·       Don’t accept claims that the Paleo diet is heart healthy. There are no long-term clinical studies to back up that claim.

·       Be aware that the Paleo diet affects your gut bacteria in ways that may be bad for your heart.

The more we learn about our gut bacteria, the more we appreciate the importance of including all 5 food groups in our diet, especially all the plant food groups.

Are Low Carb Diets Healthy?

low carb dietThe Paleo diet is not the only diet that is high in red meat and low in whole grains. The same is true for virtually all the popular low-carb diets. There are studies showing other low-carb diets also alter gut bacteria and raise TMAO levels, so there is a similar concern that they may also increase the risk of heart disease.

This is in addition to concerns about the high saturated fat consumption which increases the risk of heart disease and red meat consumption, which may increase the risk of certain cancers.

Finally, there are no studies showing that any low-carb diet is healthy long term, even the Atkins diet, which has been around for more than 50 years. Until we have long-term studies about the health consequences of low-carb diets, my advice is similar to that for the Paleo diet.

·       Don’t accept claims that low-carb diets are healthy. There are no long-term clinical studies to back up that claim.

·       Be aware that low-carb diets affect your gut bacteria in ways that may be bad for your health.

The Bottom Line

A recent study looked at the effect of the Paleo diet on an important risk factor for heart disease. Here is a brief summary of the data:

1)    The Paleo diet discourages the consumption of whole grains.

2)    Whole grains are a major source of a dietary fiber called resistant starch.

3)    Because the Paleo diet is low in resistant starch, it causes a decrease in two healthy types of gut bacteria and an increase in a type of gut bacteria called Hungatella.

4)    Hungatella metabolize compounds found in meat, eggs, and dairy to a precursor of a chemical called TMAO. This study showed that TMAO levels were 2.4-fold higher in people consuming a Paleo diet.

5)    TMAO is associated with coronary artery disease and is considered an independent risk factor for cardiovascular death.

Of course, studies like this are looking at associations. They are not definitive. What we need are long term studies looking at the effect of the Paleo diet on heart disease outcomes – like heart attack and stroke. Until we have these studies my advice is:

·       Don’t accept claims that the Paleo diet is heart healthy. There are no long-term clinical studies to back up that claim.

·       Be aware that the Paleo diet affects your gut bacteria in ways that may be bad for your heart.

·       Virtually all the popular low-carb diets discourage consumption of whole grains, so my advice for them is the same as for the Paleo diet.

The more we learn about our gut bacteria, the more we appreciate the importance of including all 5 food groups in our diet, especially all the plant food groups.

For more details on the study and what it means for you, read the article above.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease

Health Tips From The Professor