In several developed nations, including Australia and the U.S., government-funded agencies design and issue dietary guidelines for the public. These guidelines differ somewhat from country to country; however, there’s a lot of overlap with respect to the general recommendations regarding macronutrient distribution and food selection. Not everyone obediently follows the guidelines (many don’t); however, we’re all to some extent affected by them, as they greatly contribute to shaping public beliefs and opinions about diet and health, thereby sculpting the nutritional landscape in which we find ourselves.
This begs the question: Are the official dietary guidelines as good as our governments tell us they are…?
Are the official dietary guidelines really based on the best available evidence?
Among all of the different environmental factors that affect our health, food is high on the list of things that affect us the most. The food we eat has a profound impact on our health and well-being. In other words, all organizations that have the power and reach to shape the dietary habits of the population should be under close scrutiny, seeing as they basically have to make life and death decisions. If they make ill-informed and unwise decisions, people are not going to die overnight; however, some may get chronically ill and perhaps pass away prematurely.
Given this, it’s obviously important that the official dietary guidelines are based on the best available evidence. If you’ve paid attention, you’ve probably heard that some people, including the nutritional authorities who design the guidelines, claim that they are. You may also have heard that the scientific process that goes into the development of the guidelines is extremely thorough, in the sense that that no important pieces of evidence are overlooked.
In a perfect world, this would be true; however, in ours, it unfortunately isn’t. As anyone who’s knowledgeable about the evolution of the human diet, hunter-gatherers, anthropological science, and evolutionary biology will tell you, the scientific foundation that supports the dietary guidelines is not as solid and strong as the nutritional establishment claims. Far from it!
Some of the official dietary recommendations are very good. Among other things, we are told to limit our consumption of highly processed and calorie-dense foods. I think few well-informed people are going to disagree that that is a solid advice. Unfortunately though, not all of the dietary recommendations are as good as that one. For example, the dietary guidelines instruct us to eat a lot of grains. They steer us towards the bread and pasta section of the supermarket and urge us to stock up on whole grains, despite the fact that multiple lines of evidence show that a carbohydrate-rich, grain-heavy diet does not agree well with the human biology.
A building that lacks a solid foundation is not a sturdy structure
It can almost seem like the nutritional authorities that are in charge of developing the official dietary guidelines operate under the belief that we humans are elevated above nature, in the sense that they seem to pay little to no attention to our evolutionary history and the question of what we are adapted to eat. This is worrying, seeing as it’s virtually impossible to understand what constitutes a healthy human diet if one doesn’t look into the evolutionary processes that shaped our species. Furthermore, I would argue that the question of what we are well adapted to eat should be one of the very first questions we ask ourselves when we set out on the mental quest of finding the optimal human diet.
The fact is that we humans are animals. We’re not some distinct life form that doesn’t have to adhere to the laws of nature. We find it quite easy to understand what other animals are supposed to eat; however, we seem to find it very difficult to grasp our heads around the question of what we humans should put on our dinner plates.
Most people intuitively understand that caged Zoo animals should eat a similar type of diet as their wild counterparts eat in order to stay healthy. If they don’t, they get many of the same types of chronic diseases as those that plague contemporary humans.
Some people seem to operate under the belief that these principles don’t apply to us, although they of course do. The evolutionary reasons as to why gorillas, cows, and sheep sometimes get sick are similar to the evolutionary reasons as to why we humans are not completely resistant to illness.
Darwinian medicine equips us with a framework that we can use to make sense of the world and organize our thoughts about health and disease. The fact is that all diseases, regardless of what type of organism they affect, can be categorized into 6 categories according to their ultimate cause(s). The categories among these 6 that are the most important in relation to diet and health are those that contain diseases that arise primarily as a result of evolutionary mismatches.
Novel diets produce novel diseases
An overwhelming amount of the diseases and health problems that plague the modern man arise largely as a result of evolutionary mismatches, many of which are diet-genome mismatches (1, 2, 3, 4, 5). Just like caged Zoo animals, we get sick if we eat a diet that differs markedly from the type of diet we evolved to eat.
This notion is so logical and intuitively appealing that it’s a wonder some people question its merit. Not only is it logical, but it’s supported by a pile of evidence that is fighting with Mount Everest for the title of the tallest structure on Earth. We’ll not have a look at all of the review papers, clinical trials, and meta-analyses that make up this pile in today’s article; however, I would like to point out one thing, and that is that a large body of evidence shows that the infusion of dairy foods and grains into the human diet with the Agricultural Revolution adversely affected human health (2, 6, 7, 8). This is well known among evolutionary biologists; however, it’s something most nutritionists and doctors are completely unaware of, which is not surprising, seeing as most medical and nutrition students learn little to nothing about the evolution of the human diet or how the Agricultural Revolution affected the bones, teeth, height, and overall health of Homo sapiens.
Have we fully adapted to the dramatic changes in the human diet that accompanied the Agricultural Revolution? The short answer is no…
If a population of humans is exposed to a new and strong selective pressure, major changes in the gene pool of that population can occur fairly rapidly. For example, if a population is exposed to a novel and potentially deadly pathogen that kills a lot of people and/or impair the reproductive capabilities of a substantial part of the population, the prevalence of any potential alleles that confer increased protection against that pathogen will most likely increase rapidly. It won’t take that many generations before they become a markedly more dominant part of the population’s gene pool.
It’s not just changes in our microbial milieu that will get Darwin up off his chair and ready to work; changes in any other parts of our environment (e.g., food availability) can also initiate selective processes. With that said, we know for certain that evolution has not reorganized the human body so that it matches well with a grain-heavy, carbohydrate-rich diet.
Three facts that explain why diet-related diseases such as type-2 diabetes, heart disease, and colon cancer are so common nowadays
One doesn’t have to be a genius to understand why the prevalence of many diet-related diseases has increased dramatically lately; all that’s required is a basic understanding of evolutionary biology. The three following facts speak for themselves…
1. The ~10.000 years that have passed since the Agricultural Revolution barely register on the evolutionary timeline
Throughout more than 99% of the evolutionary history of our genus, Homo, all humans ate a hunter-gatherer diet composed of a mix of wild meat and plant foods. Some late Paleolithic humans may have consumed smaller quantities of certain types of cereal grains, however, the weight of the evidence clearly indicates that grains did not make up a large part of the typical diet of Paleolithic humans. It’s only very recently that the original human diet was replaced with a diet that is high in domesticated grains and dairy foods. The introduction of highly processed foods into the human diet is even more recent.
2. The changes in the human diet that accompanied the Agricultural and Industrial Revolutions were profound
The diet of Neolithic farmers differed markedly from that of Paleolithic hunter-gatherers (2, 6, 9). Perhaps needless to say, the diet of the modern man is even more different from that of the Paleolithic human (9).
3. Many of the adverse health effects that accompany the consumption of “modern foods” have little or no impact on organismal fitness
Unlike the pathogen discussed earlier, the introduction of grains and milk, and eventually also highly processed foods such as chocolate and ice cream, into the human diet did not trigger a major selection event. The reason why is simple: many, if not most, of the adverse health effects that are associated with the consumption of these foods don’t significantly impair organismal fitness.
If you eat a grain-heavy, carbohydrate-rich diet, you may put yourself at risk of developing heart disease as your get older; however, that doesn’t necessarily mean that you don’t get to pass on your genes, seeing as reproduction typically occurs early in life.
This brings us over to a very important point: Natural selection “doesn’t care” about the health of organisms, unless their health is somehow connected with their Darwinian fitness. Lactase persistence alleles didn’t spread within European populations because cow’s milk made people age gracefully and avoid degenerative disease, but rather because it’s a rich source of nutrients and calories, which fuel survival and reproduction. Genes that confer improved fitness under the prevailing conditions will be under positive selection, even if they adversely affect the health of the organisms that carry them. Hence, one should not automatically assume that it’s beneficial, health-wise, for people who are not lactose intolerant to consume milk and other lactose-containing dairy foods.
This brings us over to yet another important point: one of the primary reasons why the Paleo diet is so healthy is that our preagricultural ancestors lived in a very different environment than we do. They had to move around a lot in order to get a hold of food, they didn’t have access to basic health care, and they competed for resources (e.g., food) with other animals. A fat, sick, nearsighted, and/or metabolically deranged hunter-gatherer is not very useful. He’s probably not going to make it very long. In other words, back in the Paleolithic times, health and biological fitness were more firmly attached than they are today. This is very important to acknowledge, because it helps explain why the Paleo diet is so healthful.
Today, the situation is very different. You don’t have to be particularly healthy or fit to survive in a modern environment. Moreover, we have access to modern technology and symptom-suppressing drugs. Hence, we can’t expect natural selection to eliminate conditions such as myopia or obesity anytime soon.
Not only are traditional populations that consume hunter-gatherer type diets largely free of chronic, inflammation-driven diseases that sometimes occur early in life, but the prevalence of degenerative diseases such as heart disease is also low among traditional people eating Paleo-style diets (1, 3, 10). This can partly be explained by the fact that stereotypical Paleo foods such as meat, fruits, veggies, nuts, and roots have been a part of the human diet for a very, very long time.
I think one of the primary reasons why we find it difficult to understand that we humans are in a very similar position as sick Zoo animals that are given food they aren’t designed to eat is that we’ve never actually observed our diets change. From our perspective, a carbohydrate and grain heavy diet is the normal human diet. From an evolutionary perspective, however, it certainly isn’t. It’s a novel diet that differs markedly from the type of diet that we evolved to eat.
The committees that develop dietary guidelines for the public largely overlook this fact. They seem to pay little attention to the evolutionary evidence, as well as recent clinical trials that have looked into the therapeutic value of hunter-gatherer style diets, and instead try to piece together often conflicting results of various meta-analyses and randomized controlled trials. This is very difficult to do if one doesn’t possess a pair of evolutionary glasses. Again, some of the official recommendations are very good. Not all though, at least in my opinion.
I don’t claim to have all the answers, but if there’s one thing I know, it’s that we’ll never be able to fully comprehend what constitutes a healthy human diet if we don’t consider the question of what we’re designed to eat.
Before we wrap up, I think it’s important to point out that the diet that is optimal from a health perspective may not be optimal from a sustainability perspective. The people who have been put in charge of public nutrition don’t just consider what it’s healthy for us humans to eat; they also to some extent consider factors related to sustainability and agriculture. This is another reason why we shouldn’t trust blindly in their recommendations.
I would argue that the first and most important thing is to establish what it’s healthy for people to eat. When this knowledge is to be translated into public dietary guidelines, one can potentially make smaller adjustments and compromises so as to account more for sustainability-related issues.