Is it healthy to eat a lot of bread, pasta, and other grain-based foods? If you ask a dietitian this question, the answer you’ll get will probably be yes; on the condition that the products are mostly made up of whole grains, as opposed to refined ones. He or she may tell you that bread is the staff of life and that it, together with other foods made up of wheat, barley, and/or other cereal grains, should make up the foundation of your diet.
But what if you ask an evolutionary biologist or a nutritionist who’s involved in the emerging field of Darwinian medicine, such as myself? This time, you’ll probably get a very different answer. He or she will likely tell you that grass seeds are a novel part of the human diet and that you would be wise to think twice before you make bread, porridge, and other grain-heavy foodstuffs a major part of your diet. If you then proceed to ask why this is the case, the evolutionist you’re talking to will likely list several reasons as to why he or she advices you to limit your intake of cereal grains.
In today’s article, I thought I’d talk about 10 such reasons…
1. The introduction of large quantities of cereal grains into the human diet with the Agricultural Revolution adversely affected human health.
Cereal grains are a novel part of the human diet. Research carried out over the most recent decades has revealed that some of our preagricultural ancestors may have consumed some cereal grains; however, the weight of the evidence suggests that it wasn’t until the Agricultural Revolution about 12.000 years ago that wheat, barley, and other grass seeds started becoming an important part of the human diet. Suddenly, the human diet changed dramatically. A protein-rich, low-carbohydrate hunter-gatherer diet was replaced with a grain-based, high-carbohydrate diet. Over the following millennia, this dietary shift spread across the globe, and over time, we humans became more and more dependent on cereal grains to survive. Today, more than 10.000 years later, cereal grains are a fundamental part of the human diet all over the world. Most people on the planet consume cereal grains. Many consume them at virtually every meal.
Does this mean that cereal grains are an indispensable part of the diet of contemporary Homo sapiens? No, it doesn’t. We humans don’t need to eat grains. Throughout 99% of the evolutionary history of our genus, Homo, bread, pasta, and other similar grain-based foods were not a part of the hominin diet. Members of Homo erectus, Homo habilis, and other extinct hominin species that roamed the Earth (or at least Africa and certain parts of Asia and Europe) back in Paleolithic times rarely or never ate cereal grains.
To someone who is unfamiliar with evolutionary science, the ~10.000 years that have passed since the Agricultural Revolution may seem like a very long time; however, to a Darwinist who studies the evolution of organic beings, 10.000 years is nothing; it’s merely a tick on the evolutionary clock. What is also important to remember is that in some places of the world, it wasn’t until many millennia after the Agricultural Revolution took hold in the Fertile Crecent some 12.000 years ago that people started eating significant quantities of cereal grains.
A large body of evidence shows that the introduction of cereal grains into the human diet with the Agricultural Revolution was accompanied by a range of adverse health outcomes (1, 2, 3, 4). Early farmers didn’t grow as tall as hunter-gatherers and they were more prone to develop dental cavities, bone fractures, and other diet-related health problems (1, 2, 3, 4). Cereal grains were not solely responsible for bringing about this decline in human health; however, they were undoubtedly a major contributing factor.
2. There has been inadequate time and selection pressure for the human genome to adjust to the rapid influx of cereal grains into the human diet
The obvious question that follows from the previous section is: Has there been adequate time for natural selection to adapt the human body to a grain-heavy diet? The short answer to this question is no. In some places of the world where grains have been an important part of people’s diet for many millennia, genetic adaptations (e.g., increased AMY1 gene copy number) that confer improved digestion of certain compounds found in cereal grains, such as starch, have increased in prevalence (5, 6); however, as I’ll show throughout this article, the weight of the evidence clearly shows that we’re inadequately adapted to eat a grain-heavy diet. This is not surprising, seeing as many of the health problems that result from cereal grain consumption have little or no impact on Darwinian fitness; hence, natural selection doesn’t pay that much attention to them. Most of the genetic adaptations that have spread rapidly within human populations over the most recent millennia are not related to diet, but rather to infectious illness and other disorders that can dramatically impair an organism’s ability to survive and reproduce.
3. The consumption of bread, pasta, and other grain-based foods changes the microbiota of the upper gastrointestinal tract in adverse ways
As pointed out under point 1 on the list, the introduction of cereal grains into the human diet with the Agritulcultural Revolution was accompanied by an increased prevalence of many diet-related health problems. Many of these problems are related to oral health. Just like other animals on this planet, we humans have co-evolved with trillions of microorganisms. Each and every on of us harbors complex communities of bacteria and other critters, many of which live in our digestive systems. These communities have evolved in response to changes in their environment. Their environment is of course the human body.
With this in mind, it shouldn’t come as a surprise that our ancestors started getting more tooth decay and other similar dental health problems when they made the shift from eating a hunter-gatherer style diet to eating a farmer’s diet. It’s exactly what one would expect. It’s what the evolutionary health model predicts. The type of diet that became popular following the Agricultural Revolution imposed a very different selective pressure upon the human microbiota than the type of diet that was consumed by preagricultural hunter-gatherers. Among other things, the new diet was markedly higher in starch. The increased influx of starch into the human digestive system triggered a change in the gut microbiota. This change resulted in a genome-microbiome mismatch, as evidenced by the stack of data showing that the oral health of our ancestors got markedly worse when cereal grains were incorporated as staple components of the human diet (1, 2, 3, 4, 7)
The body of the modern man is not that different from the body of the Paleolithic man. Just like our ancestors, we are prone to develop tooth decay if we eat a lot of bread, pasta, candy, and/or other carbohydrate-rich food items, in large part because these types of foods are capable of shifting the environment of the human mouth in such a way that problematic bacteria such as Streptococcus mutans thrive (8, 9, 10, 11). If that wasn’t bad enough, these effects probably extend further down into the gastrointestinal tract, in the sense that the consumption of a grain-heavy diet, particularly one that is high in refined grains, may shift the microbiota of the small intestine in unfavorable ways (12).
4. Cereal grains contain a range of secondary metabolites and other compounds that may do us harm
All organisms that are present on this Earth have evolved various ways of defending themselves against predators and competing organisms. Whereas animals typically rely on speed, strength, or stamina to evade dangers, plants have chosen a different defense strategy. They obviously can’t run away from danger; hence, they need to find other ways of defending themselves. The strategy that many plants have chosen is to evolve various substances that are toxic to animals and microorganisms. Cereal grains contain an impressive repertoire of these types of compounds, sometimes referred to as secondary metabolites.
Some of the many substances in cereal grains that may cause us harm or impair our digestion include Wheat Germ Agglutinin (WGA), phytic acid, and alkylresorcinols (2, 13, 14, 15). At present, not many clinical trials in humans have looked into the potential adverse effects that a “normal” intake of these compounds may have upon human health, which is not surprising, seeing as it’s very difficult to assess how fairly small quantities of secondary metabolites and antinutrients affect our bodies. If they do affect us negatively, which many of them probably do, the effects are not going to be acute or dramatic; rather, they’ll be subtle, perhaps contributing to causing chronic health problems over the long-term.
Many of the studies in this area have been done in animals, often with supranormal doses of secondary metabolites. There have also been quite a few in vitro studies. The results from this type of research clearly suggests that there is some room for concern with regards to effects that substances such as WGA have on our bodies (2, 13, 14, 15). With that said, there are many factors to consider up in all of this, one of which is the evolution of our microbiomes. Some types of gut bacteria may be capable of degrading certain antinutrients, thereby potentially ameliorating the negative impact these compounds have on our health.
5. Grain-based foods have a very high carbohydrate density
One of the biggest problems with grains has to do with their content of carbohydrate. Grains such as wheat and barley are packed with starch. Starch, by itself, is not evil or dangerous; it’s just another nutrient. With that said, I would argue that it’s not a nutrient you want to take in very large quantities of, unless you’re a hard-training athlete who requires a steady supply of carbohydrate in order to perform optimally. This statement is based on everything I’ve read about nutrition and health over the years. I’m not going to be able to fully explain why I believe it’s unwise to eat a lot of starch-heavy foods in today’s article without turning it into a monster of a post. I would like to briefly highlight a couple of things though…
One of the main things that separate bread, pasta, rice, and the like from fruits and vegetables, which were the primary sources of carbohydrate in the human diet prior to the Agricultural Revolution, is that they have a very high carbohydrate density. Moreover, they contain very high levels of starch. This polysaccharide differs from other polysaccharides that we human consume in that it’s primarily digested by human-produced enzymes in the upper part of the gastrointestinal tract (mouth and small intestine), as opposed to in the large intestine, where other polysaccharides are broken down by bacteria. Hence, starch is “rapidly” broken down into glucose in the gut, which enters into systemic circulation and is transported into various cell of the body via the help of insulin.
Is this problematic? It may be. Most modern humans eat excessive amounts of carbohydrate. The types of diets that sustained hominins throughout 99% of the evolutionary history of the genus Homo were quite low in carbohydrate (1, 16). They didn’t contain anywhere near as much carbohydrate as most modern diets do, in part because they were devoid of grains, which contain a concentration of starch that is supernormal when compared to that of the foods that were a part of preagricultural hominin diets. Some grains contain as much as 70 grams of carbohydrate per 100 grams; which is a lot more than the 15-25 grams that starchy vegetables such as sweet potatoes contain. The consumption of cereal grains such as rice, in particular white rice, causes a fairly rapid rise in insulin and blood glucose levels. Unless you’re very physically active, you don’t need all of that glucose. Actually, it will likely harm you in various ways, perhaps contributing to making you gain weight.
Unlike some people, I don’t believe that the solution to the obesity epidemic is as simple as telling people to eat less carbs. With that said, there’s no doubt in my mind that a high intake of starch and other carbohydrates is unfavorable in terms of body weight management. We humans didn’t evolve to eat a diet that contains 50-60% carbohydrate by calories; rather, we evolved on high-fiber, high-protein diets. Today, we not only eat a lot more carbohydrates than ancient humans did, but we are much less physically active. Hence, our bodies are hit twice: once by a high-carbohydrate diet and once by physical inactivity.
Given all of this, it shouldn’t come as a surprise that the consumption of grains can change our microbiotas in unfavorable ways, or that several studies, as we’ll see later, have linked adherence to grain free-diets with several positive health outcomes.
6. Some cereal grains contain gluten
You don’t have to look far and wide to find a person who has heard about and is scared of gluten – a combination of proteins found in wheat and other related cereal grains. These days, it seems like “everyone” is on a gluten free diet. Is this fear of gluten justified? Both yes and no. The number of people who have celiac disease and experience acute gastrointestinal distress following the consumption of gluten-containing foods only account for a small percentage of the worldwide population.
With that said, a growing body of evidence shows that it’s not just people with celiac disease that are harmed by the consumption of gluten (3, 17, 18, 19, 20). The fact that most people who don’t have celiac disease don’t experience any acute health issues following the consumption of gluten-containing foods doesn’t necessarily mean that the gluten they are taking in isn’t harming their health. Several studies have shown that gluten may cause an immune activation and contribute to causing gastrointestinal distress, even in people without celiac disease (3, 17, 18, 19, 20). The fact is that there is a wealth of evidence linking the consumption of gluten with various health issues. The people who bash gluten-free diets tend to overlook this evidence.
To an evolutionary nutritionist such as myself, it’s not surprising that gluten has been shown to disagree with the human biology. It’s exactly what I would expect, seeing as gluten is a novel part of the human diet. In that sense, it’s no different from casein, whey, and other types of problematic proteins.
With that said, gluten, by itself, is not a toxic substance. You’re not going to die early just because your diet contains a little gluten. Moreover, simply taking gluten out of your diet is not going to make you healthy and fit, regardless of what promoters of gluten-free diets may claim. This is particularly true if you just replace gluten-containing grain products with gluten-free grain products. Gluten is just one of the many compounds in our modern diets that could negatively affect our health.
7. A compelling body of evidence suggests that grain-free diets (e.g., Paleo-style diets) are healthier than diets high in grains
Several clinical trials have found that contemporary, industrialized people who adopt a hunter-gatherer type diet tend to experience rapid health improvements (e.g., 21, 22, 23, 24, 25). They typically lose quite a bit of weight in a short period of time, their insulin and leptin sensitivity improve, their triglyceride levels decline, and their ratio of total to HDL cholesterol goes down, among other things. Some of these studies compared hunter-gatherer diets to other prudent diets, such as the Mediterranean diet and the Diabetes diet, and found that the former are superior with regards to the impact they have on various health outcomes.
To someone who is not knowledgeable about evolutionary nutrition, these results may seem unexpected; however, to someone who has delved into the research pertaining to the evolution of the human diet, they probably don’t. It’s not surprising that westerners who go on a hunter-gatherer type diet lose weight and get healthier, it’s exactly what one would expect, seeing as the diets that supported the evolution of the human body, with its large brain and strong glutes, were hunter-gatherer diets.
The human metabolism, digestive system, and overall physiology hasn’t changed that much in 10.000 years; hence, it’s not surprising that randomized trials have found that Paleolithic diets agree with the body of the modern man.
8. Grains contain a lot of insoluble fiber that can irritate the gut
Anecdotal reports suggest that some people experience better digestive health when they take whole grains out of their diet. I don’t find this surprising, seeing as whole grains are rich in a variety of compounds that could undermine gastrointestinal health. As previously explained, they contain many antinutrients and are also high in starch, a nutrient that could shift the configuration of the microbiota of the upper gastrointestinal tract in unfavorable ways if it’s consumed in large quantities. Another characteristic of cereal grains is their high content of insoluble fiber.
If you ask a dietitian whether he or she thinks grain fibers are good for you, he/she will likely say that they are. Personally, I’m not convinced that this is true. Actually, I think the opposite may actually be the case. Grains differ from fruits and vegetables in that they primarily contain insoluble fiber, as opposed to soluble ones. Some grains, such as oats, are quite high in soluble fiber; however, they are the exception rather than the norm.
Insoluble fibers are often praised for the effects they have on gastrointestinal transit time (they make you go to the toilet more often) and stool bulk (they make you pass more feces). Personally, though, I’m not so sure that these effects are necessarily beneficial. If you’re constipated or your stools don’t look healthy, you’re probably much better off taking steps to fix your diet and microbiota, as opposed to stuffing yourself with more whole grains.
The idea that grain fibers aren’t as great as the typical dietitian thinks is supported by studies indicating that many of the beneficial health effects that have been linked with fiber consumption (e.g., improved blood cholesterol values) are primarily caused by the intake of soluble fiber, not by the consumption of insoluble ones (26, 27, 28). This is not surprising, given that soluble fibers tend to be fermented by bacteria to a greater extent than insoluble ones. The proportion of soluble to insoluble fiber tends to be higher in fruits and vegetables than in cereal grains (16). Moreover, fruits and vegetables typically contain more total fiber than grains (on a calorie-by-calorie basis).
Some of the fibers found in cereal grains such as oats act as fuel for the colonic microbiota and can enhance the production of butyrate and other short-chain fatty acids in the large intestine; however, these potential beneficial effects dwindle in comparison to the potential adverse effects that grain consumption can have. The fact is that you can get plenty of fermentable fibers into your body via the consumption of vegetables, given that you purposely include high-fiber varieties in your diet. You don’t need to eat grains to get some fiber into your gut. With that said, if you’re going to eat grains, oats may be a good choice, as they are high in beta-glucan, a type of carbohydrate that is broken down by gut bacteria.
9. Grains are inferior to fruits, vegetables, and other foods that were a part of preagricultural human diets with regards to their nutritional profile
Are grains nutrient-dense? The answer to this question will depend on what you compare them against. When compared to sugary doughnuts and other processed foods, cereal grains such as wheat are certainly high in vitamins and minerals; however, when compared to fruits and vegetables, they aren’t (2, 29). And they definitely aren’t if you compare them against organ meats or other nutritional powerhouses.
Not only are cereal grains less nutrient dense than fruit and vegetables, but they are also low in many vitamins and minerals that we humans need to operate at a peak capacity (2, 29). Hence, it’s not surprising that there are marked signs of nutritional stress upon the skeletons of Neolithic farmers who sustained themselves on diets rich in just one or a couple of species of grains (1, 2, 3, 4). Finally, grains have a very high omega-6 to omega-3 ratio and are low in several essential amino acids (2).
10. Grains may be addictive
Many of the foods and beverages that are a part of contemporary human diets have addictive properties. These foods and drinks include, but are not limited to, cheese, chocolate, wine, and coffee. Certain types of grains can probably also be added to this list. Not only are grain-containing foods such as bread fairly energy dense and high in carbohydrate, but they also contain substances such as gluten that has been shown to possess opoid-like properties (30, 31). This could help explain why a lot of people find it very hard to give up bread, pasta, and other grain-based foods. Perhaps needless to say, eating bread is not as bad as doing crack; however, it could have some mild addictive effects.
What about the studies that seem to show it’s beneficial to consume a lot of whole grains?
As any dedicated nutrition student and well-informed nutritionist knows, several randomized-controlled trials and meta-analyses have linked the consumption of whole grains with a variety of positive health outcomes (e.g., improved blood lipid composition) (e.g., 32, 33). A lot of people look at these studies and jump to the conclusion that it’s healthy to eat a lot of whole grains. What these folks fail to recognize is that virtually all of the studies in this area have compared “prudent” whole grain-containing diets with less prudent diets low in whole grains, or they’ve compared whole grains with refined grains.
Typically, one group of participants are instructed to eat X amount of whole grains every day, whereas another group is instructed to eat the same amount of refined grains. After some time, perhaps 6 or 12 weeks, the outcomes (e.g., fat loss, LDL levels) of the study are assessed. Perhaps not surprisingly, most of the studies that are set up this way find that the participants in the whole-grain group experience greater health improvements than those in the refined-grain group.
Unlike what some people seem to think, this does not prove that it’s healthy to eat a lot of whole grains. It just means that it’s probably better to eat whole grains than to eat refined grains (Shocking, right?). It doesn’t necessarily mean that it’s better to eat whole grains than to not eat grains. To investigate this idea, one would have to compare grain-free diets with grain-containing ones. As discussed under point 7 on the list, the studies that have conducted this comparison indicate that it’s better to consume little or no whole grains than a lot of whole grains.
Unfortunately, the nutritional establishment has not yet recognized these things. Government-issued nutritional agencies advice people to eat a lot of whole grains, a recommendation that is largely based on studies that have compared the healthfulness of whole grains with that of refined grains.
Should everyone stay away from cereal grains?
I’ve made the case many times here on the site that it’s unwise to eat a lot of cereal grains. However, I’ve also pointed that some people, such as hard-training athletes who do a lot of anaerobic exercise, benefit from including some cereal grains in their diet. Our ancient ancestors were very physically active, but they obviously didn’t perform heavy squats, military presses, or other similar types of exercises that many gym goers and athletes perform today. These types of activities are highly glycolytic when performed at high intensities.
Other factors besides physical activity levels/patterns can also affect a person’s dietary needs, such as health status. The dietary needs of sick people tend to differ from that of healthy folks.
Is there something I can do to make grains less harmful?
The short answer to this question is yes. The problem we have today is not just that we eat too much bread, pasta, and other grain-based foods, but also that the way we process and prepare the cereal grains we eat is very different from how it was traditionally done. Many traditional societies soaked, sprouted, and/or fermented the grains they were eating. These traditional processing techniques change the nutritional characteristics of grains and make them easier to digest. Fermentation in particular is a very effective way of making grains healthier and easier to digest, as it breaks down many antinutrients and reduces the glycemic index of the grains.
This is to say that not all grain-containing foods are created equal. A homemade sourdough bread is a lot healthier than a refined bread found at the grocery store. With that said, if a person came up to me and asked whether it would be best for him to eat a Paleo-style diet or a diet that contained a lot of traditionally prepared grain-containing foods, I would most certainly advise him to go with the original human diet.