Do We Really Need to Brush Our Teeth?

Many diseases and health problems that we – contemporary humans – consider to be largely unavoidable, such as acne vulgaris, a skin disorder that afflicts more than 90% of the adolescent population in some westernized countries, and malocclusion, a very common condition nowadays that is characterized by a misalignment of the upper and lower jaw, are actually not a normal part of the human existence, in an evolutionary sense. It wasn’t until quite recently in our evolutionary history that these disorders became common. Among hunter-gatherers, they are rare (1, 2, 3).

Scientific evidence suggests that this may also be the case for dental caries, which quickly develops inside the mouth of the modern, sugar-heavy man if he doesn’t brush and clean his teeth. This condition was with a high degree of certainty quite rare in Paleolithic times (4, 5, 6, 7, 8). Today, however, it’s so ubiquitous that one would be hard pressed to locate a grown individual who has never had to visit a dentist to deal with a cavity or two.

In order to limit our risk of developing tooth decay, we brush our teeth relentlessly and bombard them with chemicals in the form of toothpaste and mouthwashes. Is all of this necessary? Does everyone need to brush their teeth…?

Tooth decay hasn’t always been as ubiquitous as it is today

The idea that the prevalence of dental cavities among our Paleolithic forebears was much lower than what it is among contemporary, westernized populations is supported by several lines of scientific evidence.

Examinations of ancient fossil remains have revealed that Paleolithic hunter-gatherers generally had well-developed dental arches and little or no tooth decay (4, 5, 6, 7, 8). The skeletons of early farmers, on the other hand, exhibit marked signs of nutritional stress, often including rotten teeth (4, 5, 6, 7, 8). These findings are fairly consistent, in the sense that multiple studies suggest that the Agricultural Revolution was accompanied by a deterioration of the condition of the human oral microbiome and teeth. Not only that, but a big pile of data, including data derived from Dr. Weston Price’s thorough examinations of the health status of indigenous populations, show that westernization is always accompanied by tooth decay (9, 10, 11).

A recent study found that the Hadza hunter-gatherers do get tooth decay (12). What’s important to remember though is that the Hadza are not a perfect replica of our ancient ancestors. Among other things, the Hadza take in a lot more starch and sugar (in the form of honey) than most other hunter-gatherers. They probably also take in more of these nutrients than Paleolithic, African foragers did.

Not all ancient hunter-gatherers had excellent, disease-free teeth; however, the available evidence clearly suggests that their teeth were generally in much better shape than those of Neolithic farmers and most modern humans.

The carbohydrate-heavy modern diet isn’t kind to our teeth

It’s not really surprising that foragers rarely get tooth decay, seeing as they generally eat little or no cereal grains and no highly processed, sugar-heavy foods. Just like all other organisms on this planet, the bacteria that live in our oral cavities need energy to survive. They depend on us – their hosts – to provide them with this energy. If we don’t feed them, they die.

Different types of oral bacteria have different “nutritional requirements”. Some bugs, including the caries-causing bacterium Streptococcus mutans, thrive in the presence of sugar (12, 13). They are really fond of popsicles, doughnuts, and cookies. Many contemporary humans consume these types of sugary foods on a regular basis, and also routinely use antibiotics and/or other drugs; hence, it’s not surprising that we’re in the midst of a tooth decay pandemic.

We’ve become so used to the omnipresence of highly processed foods in our environment, as well as the idea that it’s normal to depend on a dentist to keep one’s teeth healthy, that we completely overlook the fact that our teeth are capable of taking care of themselves (at least most of the time) as long as we don’t subject them to environmental stimuli that they are evolutionarily unaccustomed to.  

When left untreated, dental cavities can compromise organismal fitness; hence, it’s not surprising that the Paleolithic diet is a caries antagonist

In order to understand why tooth decay, as well as many other health problems that are very common nowadays, were rare in the distant past, we not only have to determine how the environment of the modern man differs from the one that ancient humans lived in, but we also have to examine the selective pressures that have acted on human populations throughout evolutionary time.

It’s not surprising that obesity, myopia, type-1 diabetes, and many other health disorders are rare among hunter-gatherers, seeing as a person who suffers from one or more of these conditions will find it difficult to survive in a natural environment, where one has to walk or run long distances and track wild animals in order to get a hold of food, and modern medicine, including its arsenal of insulin pumps and drugs, is nowhere to be found.

Tooth decay is also a condition that can compromise biological fitness, seeing as untreated cavities may cause pain and discomfort, as well as in some instances infections, and in some extreme cases, even death. If our primal forebears had eaten a lot of grains and sugary foods, we humans would undoubtedly have been less prone to develop tooth decay, as well as other oral health-related problems, following the consumption of a carbohydrate-heavy diet, seeing as natural selection would have favored those ancestors of ours who did well on such a diet.

This idea, which can be extended to include virtually everything that has to do with nutrition and health, as well as many other facets of the human existence, is extremely powerful, in the sense that it helps us make sense of why we are designed the way we are and organize our thoughts regarding what type of environmental stimuli our bodies need in order to function appropriately. A lot of people know that we need take in vitamin D in order to avoid getting scurvy, that our teeth suffer if we eat a lot of highly processed foods, and that our bones degenerate if we don’t exercise on a regular basis; however, most people are probably incapable of explaining why that is. This isn’t surprising, seeing as that’s not something that’s taught in most schools (For example, nutritionists learn that we need to take in X grams of protein in order to avoid developing a protein deficiency, but they don’t learn why we need that exact amount) or something that our society as a whole pays much attention to. This is unfortunate, because as pointed out above, evolutionary theory can illuminate many aspects of the human existence.

The explanation as to why our dietary requirements are as they are, why we look and behave the way we do, and why modern, sugary foods don’t agree with our bodies and teeth can be found in our evolutionary past.

So, do we need to brush our teeth?

Today, the practice of brushing one’s teeth is so ingrained into our culture that most people would probably find the thought of not brushing their teeth very off-putting. They are so used to going to bed with a taste of Colgate or Sensodyne in their mouth that the experience has become a natural, almost essential part of their lives. Few people seem to acknowledge how abnormal this behavior actually is. No other animals on this planet brush their teeth with toothpaste. Moreover, with respects to our species, the practice of brushing one’s teeth every night is an evolutionarily novel one. Our primal forebears may have used small sticks to clean their teeth (14) and some may perhaps have chewed on leaves or other natural substances, some of which may have had antimicrobial properties; however, they obviously didn’t have access to chemical-laden toothpastes or brush their teeth every night before going to bed.

Does that mean that we shouldn’t brush our teeth either? Not necessarily… We have to account for the fact that our environment, including our nutritional milieu, differs markedly from that of our Paleolithic forebears. Not only that, but it’s important to remember that lowering one’s risk of tooth decay isn’t the only legitimate reason to brush one’s teeth. Brushing can also help improve the appearance of one’s teeth.

If you eat a fairly strict Paleolithic, hunter-gatherer type diet, low in sugary and starchy foods, you will likely find that your teeth don’t require much brushing to stay white and free of cavities; however, if you eat grains and/or processed foods on a regular basis, you’ll obviously have to pay more attention to dental hygiene. Personally, I can almost feel my teeth screaming for attention when I eat something that’s high in starch and/or refined sugar. On these occasions, I always thoroughly brush my teeth with toothpaste before going to bed.

If I stick with a strict Paleolithic diet, however, I don’t feel like I need to brush my teeth with toothpaste. I do brush them and use a tooth pick to clean the area in-between the teeth, as I like the clean feeling it gives me, but I generally don’t use toothpaste, mouthwash, or any other chemical-laden substances. Actually, I find the thought of using these products quite off-putting if I’ve not eaten anything that is known to cause a proliferation of unfriendly oral bugs. I very much question the idea that it’s healthy to alter the microbial ecosystem of one’s mouth by bombarding it with various chemicals.

The bottom line

Poor oral health doesn’t just set the stage for tooth decay; it may also lead to other, more systemic health issues. Hence, it goes without saying that it’s important to keep one’s teeth and oral cavity healthy. Oral hygiene is obviously important in this respect. That said, Darwinian wisdom suggests that many of the oral health-related problems that modern dental practitioners deal with on a daily basis are not intrinsic to the human condition, but rather arise as a result of genome-environment mismatches, in particularly mismatches related to diet.

If you eat a carbohydrate-heavy, sugary diet, you will, with a high degree of certainty, find that you need to regularly brush your teeth with toothpaste in order to keep oral pathogens from destroying your oral health. If you eat a diet resembling the original human diet and otherwise take good care of your oral microbiota, however, you won’t have to pay that much attention to your teeth. You will likely find that your teeth look and feel better if you clean them on a regular basis, but you certainly won’t need an arsenal of oral-health care products to keep your oral microbiota from turning against you.