Lectins, gluten, protease inhibitors, phytic acid… If you’ve been reading about cereal grains on one or more of the many Paleo blogs that are out there, you’ve undoubtedly heard about these compounds, which are found in bread, breakfast cereals, and other grain-based food products, and the potential harmful effects they can have on human health. Moreover, you’ve probably read that you should stay away from grains, since they are low in many important vitamins and minerals, contain a lot of starch, and raise your insulin levels. Although there are some people in the ancestral health scene that paint a more positive picture of this food group, it’s safe to say that historically, bread, pasta, and oatmeal haven’t gotten a lot of positive press within this movement. Is this vilification of cereal grains justified?
Before we jump in I want to begin by making it clear that I’m a big proponent of pretty much everything that has to do with evolutionary health promotion, ancestral health, etc. (As you know if you’ve been reading this blog for some time). Moreover, I strongly believe that the conventional nutritional and medical community are in desperate need of some influx of evolutionary health wisdom. That being said, the goal has to be to find the “truth”, not to slavishly follow a strict set of rules or principles. I think it’s important to look at both sides of the evidence, try to objectively examine things and avoid letting personal biases come in the way when interpreting the data, and be open to adjusting one’s opinions in the light of new information.
Recently, I’ve been thinking and reading a lot about the pros and cons of eating cereal grains, and I’ve also been experimenting by making changes to my own diet. The result of this process is that I’m left with a more nuanced perspective on this topic than what I had previously. In this post I’ll briefly summarize the pros and cons of eating cereal grains, before I give you my current reflections and opinion on all of this.
The Bad: 8 arguments that speak against eating cereal grains
1. There has been inadequate time and selection pressure for the human genome to adapt to the rapid influx of large quantities of cereal grains (particularly refined types) into the human diet
Today, cereal grains such as wheat and barley are important staple foods all around the world, and a lot of people would probably say that a diet that is devoid of grains is a very strange or peculiar diet. However, as the readers of this blog know well, it hasn’t always been like this. Cereal grains didn’t make their way into the human diet in any significant quantities until the Agricultural Revolution started sweeping the globe about 10.000 years ago. This may seem like a long time ago, but from an evolutionary perspective, it’s merely a couple of ticks on the clock.
When compared to the tiny microorganisms that live all around us and in and on our bodies, humans evolve at an extremely slow pace. As I’ve repeatedly pointed out here on the blog, we’re still – to a significant extent – hunter-gathers from a genetic perspective. There has been inadequate time and selection pressure for the human body to adapt to many of the recent changes in the human diet. This includes, among other things, the dramatic increase in cereal grain consumption (in particular refined grains).
2. The transition from a Paleolithic diet to “Neolithic”, grain-based diet was accompanied by an increased incidence of many diet-related disorders
An increased incidence of a wide range of diet-related health problems, including iron deficiency anemia, tooth decay, and several bone mineral disorders, accompanied the Agricultural Revolution, either at first or gradually (1, 2, 3). Moreover, early farmers didn’t grow as tall as preagricultural humans (1, 2).
All of these unfavourable health effects came largely as a result of the transition from a Paleolithic diet to “Neolithic”, grain-based diet; a diet that in comparison was low in many vitamins and minerals and high in starch and antinutrients (1, 2, 3). This dietary transition undoubtedly resulted in changes to the human microbiome – especially oral and gut – and altered gene expression patterns. Suddenly we collided with a diet that natural selection had never adapted us for.
3. The scientific foundation underlying the recommendation to eat a lot of cereal grains is not rock solid
Cereal grains didn’t end up at the bottom of the food pyramid because there’s conclusive evidence to show that a grain-based diet is healthy for us. Rather, one of the key reasons they ended up there is that cereal grains are a cheap and accessible source of calories that have long been an essential part of the human diet all over the world. As Denise Minger explains in here book “Death by Food Pyramid”, the science underlying the food pyramid is far from rock solid.
The advice to eat more whole grains is in large part based on studies that have investigated the health effects of consuming whole grains vs. refined grains. Naturally, these studies conclude that whole grains are superior. However, the results of intervention studies that have compared the “healthfulness” of a diet that’s rich in whole grains with the healthfulness of a Paleo Diet, which is completely devoid of grains, indicate that the The Paleo Diet may be superior (4, 5, 6, 7, 8).
4. Cereal grains have a very high carbohydrate density
While the high carbohydrate content of cereal grains may not be a problem for a hard-training athlete, it can certainly be for a sedentary individual who wants to lose weight and/or are insulin resistant.For millions of years, our ancestors got most of their carbohydrates from fibrous fruits, nuts, seeds, and tubers and other vegetables. When compared with cereal grains, these foods have a very low carbohydrate density and elicit a low insulin response.
5. Cereal grains contain potentially harmful antinutrients
Cereal grains contain a wide range of proteins and antinutrients (e.g., lectins, phytic acid) that may impair nutrient absorption, disrupt normal gut physiology, and contribute to the manifestation of chronic inflammation and autoimmune diseases by increasing intestinal permeability and initiating a pro-inflammatory immune response (1, 9, 10, 11).
6. Cereal grains have a relatively poor nutrient profile
When compared with fruits and vegetables, cereal grains are less nutrient dense (on a calorie-by-calorie basis) and lower in prebiotic fiber (1, 12). Moreover, cereal grains are deficient in one or more vitamins and essential amino acids (3), and none of the domesticated cereals have adequate iron, calcium, or zinc (3). In itself, this doesn’t say that cereal grains are unhealthy. However, it highlights one of the many problems of relying on cereal grains as a staple food.
7. Cereal grains (in particular refined varieties) may adversely affect the gut microbiota and/or intestinal barrier function
Cereal grains, in particular refined grains, may alter the gut microbiota in such a way that there is an increased absorption of bacterial endotoxins from the small intestine (4)
8. Some grains may have addictive properties
Cereal grains such as wheat contain opioid peptides that bind to opioid receptors in the brain and may trigger addictive-like responses (13)
The good: 8 arguments that speak in favor of eating cereal grains
1. There may have been insufficient time and selection pressure for the human genome to adjust to the rapid influx of cereal grains into the human diet. However, we have to remember that the second genome in the human body, the human microbiome, is also important when it comes to adaptation to dietary changes
The gut microbiome can be thought of as a bridge between the human body and the external environment. The foods you eat all affect the gut microbiota in some way. Moreover, over the last couple of years it has become increasingly clear that the gut microbiome plays an important role in the context of diet adaptation. If we had to rely on mutations and selection within our human genome as our only means of adapting to new food groups, things wouldn’t have been easy, particularly for our ancestors, who didn’t have constant access to the “rapidly” digested sugars, starches, and fats that we have today.
One of the main reasons humans are able to thrive on very different diets is that the gut microbiome is able to adapt to new dietary practices – as long as the necessary microbes (i.e., bacteria that carry genes that code for enzymes that facilitate the breakdown of the foods in question) are present. This adaptive process is important to keep in mind when discussing the health effects of consuming cereal grains.
Recent studies have shown that certain species of bacteria collected from the gastrointestinal tract of humans can degrade many of the potentially “harmful” compounds found in grains, such as gluten (14, 15) and phytate (16). Moreover, over the last decade it has become increasingly clear that the rapidly increasing rates of celiac disease and other gluten-related disorders may be largely caused by changes to the human gut microbiome (think antibiotics, c-sections, and hygienic living conditions) (17, 18, 19, 20). In other words, it’s likely that one of the main reasons one person does well on a grain-based diet while another doesn’t, is that former harbours a gut microbiome that is better adapted to the diet in question. This may also work the other way around, in the sense that some people may not do so well on a diet that is devoid of grains.
Within the ancestral health community there is a lot of talk about how the mismatch between the human genome and the contemporary, Western diet affects human health – and rightly so; there’s little doubt that this discordance underlies many of the diseases that plague us in modern societies. That being said, I think it’s very important to remember that we also have a second genome within our body. Is it possible that the reason some people don’t do well on a Paleo Diet is that they harbour a gut microbiome that is better suited for a grain-based diet? In other words, that there may be a mismatch between the gut microbiome and the grain-depleted diet. I suspect so.
Let me briefly explain my thought process… The gut microbiotas of our ancestors would have evolved as they transitioned over to more grain-based diets during the Agricultural Evolution and have continued to change ever since in response to alterations in diet and lifestyle habits (21, 22, 23). The first seeding of the microbiota occurs as bacteria are transferred from mum to offspring during birth, breastfeeding, and other types of contact, meaning that a familial microbiome may pass down through generations. In other words, if your mother and close family ate a iot of grains – and did well on such a diet – chances are you’ll do better on such a diet yourself. It may even be that you find that you don’t do so well on strict Paleo Diet, because your gut microbiome is poorly matched to that diet. While the microbiome can adapt rapidly to changes in diet, adequate adaptation is only possible if bacteria that are able to degrade the newly introduced foods are present.
2. A strict contemporary Paleo Diet may provide less than optimal amounts of dietary fiber
The foods we have access to today differ in several respects to those that hunter-gatherers and non-westernized, traditional cultures consumed. For example; we obviously don’t have access to the extremely fibrous tubers that African hunter-gatherers (e.g., the Hadza) have been known to consume. A strict contemporary Paleo Diet may provide less than optimal amounts of dietary fiber. This is not a fault of the Paleo Diet per se, but rather a result of changes in how we produce and process our food.
Domesticated fruits and vegetables tend to be markedly less fibrous than their wild counterparts (12). Moreover, non-domesticated varieties typically contain much less insoluble, hard-to-chew roughage. A contemporary Paleo Diet – particularly one that contains a lot of meat, fat, and cooked plant foods – is extremely “soft” when compared to a true Paleolithic diet.
3. Recent studies suggest that cereal grains may have been a more important part of our Paleolithic ancestors’ diet than previously thought
As I’ve pointed out previously on the blog, several lines of evidence indicate that our Paleolithic ancestors did not consume large quantities of cereal grains. This actually goes without saying, as it takes a lot of work and effort to collect, process, and prepare wild cereal grains. Optimal foraging theory suggests that it simply wouldn’t have been feasible for the typical Paleolithic hunter-gatherer to consume large quantities of cereal grains. That being said, it’s been known for a long time that smaller amounts of cereal grains were consumed by Paleolithic hunter-gatherers in certain areas of the word, perhaps when other food resources were scarce. Recent studies (e.g., 24, 25, 26) have added additional support to this notion.
4. The harmful effects of grain-antinutrients may have been overblown
While it is true that wheat germ agglutinin, phytic acid, and many of the other antinutrients found in grains may disrupt normal gut physiology, impair mineral absorption, or have other adverse effects, it’s important to note that most of the studies that have looked into these compounds have been done in animals or in vitro. Moreover, the amounts that are used typically far exceed what you get from common foods. The processes that can be observed in a petri dish may not adequately reflect what goes on in the human gastrointestinal tract. This becomes particularly true when we consider the fact that each and every one of us harbor a unique and complex microbial ecosystem that interacts with the food we eat. While I definitely think some caution is warranted, I’m not overly concerned with the antinutrients found in grains.
5. Starch is not the evil nutrient that some people make it out to be
As I’ve pointed out many times here on the blog, there’s no reason to completely shun starchy food. This is particularly true for athletes. Many gym goers, athletes, and fitness enthusiasts these days follow a training program that has little in common with the physical activity pattern of a hunter-gatherer. A strict Paleolithic Diet may not be the best choice for these individuals, particularly if they perform a lot of anaerobic activities. Some people find that they perform well in a keto-adapted state, but this is obviously not a viable and effective strategy for everyone.
6. There is a lot of scientific research linking the consumption of whole grains with positive health outcomes
If you ask a dozen dietitians and nutritionists whether they think whole grains are healthy, chances are most, if not all, will say yes. This isn’t surprising, as virtually all nutrition students learn that whole grains are an essential part of a healthy diet – and that there’s solid scientific evidence underlying the recommendation to eat whole grains on a regular basis. As I mentioned in the list above, the problem is that a lot of the studies in this area have compared diets that contain whole grains with diets that contain refined grains. These studies only tell us whether whole grains are superior to refined varieties, not whether a grain-containing diet is superior to a diet that is completely devoid of grains. That being said, it’s important to acknowledge that the evidence in this area is not clear-cut either way.
7. Several non-westernized populations have low rates of chronic diseases of civilization “despite” eating diets high in cereal grains
We don’t have to look far and wide to find examples of people who are lean, healthy, and long-lived “despite” eating grain-based diets. For example; Okinawa Island in Japan is famous for the longest disability-free life expectancy in the world. The traditional diet on this island is high in rice and carbohydrates. Also, as I’ve pointed out on the blog before, some of the healthy, traditional cultures Dr. Weston A. Price examined on his trips around the world in the early parts of the 20th century ate grain-heavy diets.
That being said, it’s very important to point out that these observational studies don’t by any means provide evidence that we should all be eating a lot of cereal grains, as there are certainly many other confounding factors that could help explain the good health of these peoples. Moreover, we can’t exclude the possibility that they would be even healthier if they replaced some of the grains they were eating with meat, fish, eggs, vegetables, etc.
8. Changes in AMY1 copy number reflect adaptation to increased starch consumption
There has probably been some selection for greater copy numbers of the salivary amylase gene (AMY1) in cultures that eat diets high in starchy plants. In other words, your ability to tolerate a high intake of starch may in part depend on your ancestry. Here’s what a recent review paper had to say about starch consumption and changes in AMY1 copy numbers during human evolution:
Starch consumption is a prominent characteristic of agricultural societies and hunter-gatherers in arid environments. In contrast, rainforest and circum-arctic hunter-gatherers and some pastoralists consume much less starch1–3. This behavioral variation raises the possibility that different selective pressures have acted on amylase, the enzyme responsible for starch hydrolysis4. We found that salivary amylase gene (AMY1) copy number is correlated positively with salivary amylase protein levels, and that individuals from populations with high-starch diets have on average more AMY1 copies than those with traditionally low-starch diets. Comparisons with other loci in a subset of these populations suggest that the level of AMY1 copy number differentiation is unusual. This example of positive selection on a copy number variable gene is one of the first in the human genome. Higher AMY1 copy numbers and protein levels likely improve the digestion of starchy foods, and may buffer against the fitness-reducing effects of intestinal disease. (27).
What does this mean for you?
While I’ve never outright demonized cereal grains on this blog, I’ve made the case several times that most people would benefit from reducing their intake of this food group. This is a statement I stand by. The average Joe eats way too much bread, pasta, breakfast cereals, pastries, and other grain-based foods and would probably benefit greatly from replacing some of these foods (in particular the ones that primarily contain refined grains) with more nutrient dense foods such as grass-fed meat, eggs, fish, and vegetables. That being said, I don’t think completely eliminating cereal grains from the diet is necessarily the way to go for everyone.
While we can learn a lot about how we should eat to achieve good health by studying the dietary practices of our ancestors, we should be cautious not to oversimplify things by thinking that we’re best off emulating every aspect of our hunter-gatherer ancestors’ diet. We have to keep in mind that most people these days have a lifestyle that is very different from that of a Paleolithic hunter-gatherer. While sedentary individuals often do well on a low-carbohydrate diet, many gym goers, athletes, and fitness enthusiasts find that they require some dense sources of starch in their diet to perform optimally.
Perhaps the most compelling argument for eating some whole grains and/or legumes is that the amount of fermentable fiber you get through a strict, contemporary Paleo Diet could be lower than optimal – even if you consciously seek out the most fiber-rich fruits and vegetables you can find. While some people may find that they manage to achieve great gut health on a strict Paleo Diet, others don’t. This isn’t surprising, as most of the fruits and vegetables that are available at the supermarket don’t contain that much fiber. Eating some whole grains and/or legumes can help give the fiber content of the diet a marked boost.
Finally, I want to make it clear that when it comes to diet, there is no one size fits all. While there is a set of general dietary principles that everyone who’s looking to achieve good health should adhere to, there is no such thing as a strict set of rules that works for all people. Some find that they do better on a diet that is relatively high in carbohydrates, while others do better on a more low-carb approach.
Whether you do well with including cereal grains in your diet or not depends on several factors, such as your activity levels, gut microbiota composition, AMY1 gene copy number, gluten sensitivity, and gut permeability. Perhaps needless to say, not all grains are equally healthy. If you’re going to eat grains, it’s important to consider which types you’re going to eat, as well as how you process and prepare them – but that’s a topic for another day…
Personally, I’ve never completely shunned grain-based foods, but cereal grains haven’t been a major part of my diet these last several years. However, recently I added some whole grains to my diet, both as a way to boost my fiber intake and help me fuel my current workout routine.
Now I want to hear from you: What are your thoughts on all of this? Do you eat grains on a regular basis?