The Oral Disaster: How Carbohydrates Have Turned the Human Mouth Into a War Zone

girl-lollipopIn my recent article entitled 10 Reasons Why Grains Shouldn’t Be at the Bottom of the Food Pyramid I pointed out that the introduction of large quantities of cereal grains into the human diet with the Agricultural Revolution steered the human oral microbiome onto a new evolutionary path. From the perspective of Homo sapiens, this path was not easily traveled. A large body of evidence shows that Neolithic farmers got more tooth decay than Paleolithic hunter-gatherers and were more susceptible to develop periodontal disease, in large part because their starchy diet induced the growth of caries-causing oral bacteria (1, 2, 3, 4, 5).

In the years that have passed since then, the human oral microbiome has not returned to its Paleolithic state. On the contrary, additional infusions of carbohydrate-heavy foods into the human diet, in conjunction with other diet and lifestyle shifts, have further altered the composition of the human oral microbiome (1). In addition to eating a lot of grains, many contemporary humans also consume significant quantities of foods rich in refined sugar, such as chocolate, cupcakes, and ice cream. Unfriendly oral bacteria such as Streptococcus mutans love these foods (6, 7, 8, 9). They crave them and rapidly grow inside the mouths of people who eat them, tearing down the defensive barriers of their teeth.

Can we trust that Colgate keeps us our of harms way?

Unlike Neolithic farmers, we – contemporary humans – have the option of brushing our teeth with toothpaste and rinsing our mouths with chemical-laden mouthwashes, thereby curbing the growth of proinflammatory oral bacteria. What a lot of people don’t realise though is that these practices don’t eradicate the oral health problems that accompany the consumption of a carbohydrate-heavy diet; they only suppress some of the symptoms of the problems.

If you’re a regular reader of this site, you can undoubtedly remember hearing that statement before, although in a different context. The approach of suppressing or covering symptoms, as opposed to preventing or curing illness, is typical of modern health care. Via the use of drugs, chemicals, and technology we try to alleviate our suffering, as well as the suffering of domesticated plants and animals that have been ridden with disease. What we typically fail to acknowledge is that this approach merely masks some of the problems we seek to eliminate; it doesn’t tear up their roots and eradicate them.

We’re at war with the proinflammatory bugs that thrive in our mouths as a result of our high carbohydrate intake. Via the use of mouthwashes, toothpaste, and other weapons we have in our arsenal, we manage to keep some pathogens at bay; however, we’re not able to fully protect our bodies against harm. The only way we can bring about a state of peace is by changing the way we eat. 

The human oral microbiome has changed a lot recently

The fact is that the mouth of the modern man is in a chronic state of illness. Evolution didn’t sculpt our bodies in such a way that we require the help of Colgate to keep our teeth healthy. Rather, the reason we need chemical-laden dental care products to keep oral bugs such as S. mutans from taking over our oral cavities is that the modern, carbohydrate heavy diet produces an oral microbiome that matches poorly with the human genome. In other words, dental cavities are (largely) a manifestation of a genome-microbiome mismatch.

This is not to say that I’m advising people not to brush their teeth; all I’m saying is that no dental care products completely undo the damage that processed, carbohydrate-heavy foods have on our teeth. The only way to avoid this damage is to avoid doughnuts, candy, and the like.

Here’s what a 2013 review paper describes the recent evolution of the human oral microbiome:

Overall, it is clear that modern Europeans have much lower oral microbial diversity than either Mesolithic or pre-Industrial Neolithic groups, including fewer bacteria associated with good health (Ruminococcaceae), periodontal disease-associated taxa (e.g., Porphyromonas gingivalis, Tannerella and Treponema) similar to early agriculturists, and a markedly higher abundance of (now ubiquitous) pathogens such as Streptococcus mutans. Perhaps more importantly, the decline in overall oral microbial diversity indicates that over the past few hundred years, the human mouth has become a substantially less-biodiverse ecosystem. In both a human-associated microbiota and macroecological context, higher phylogenetic diversity is associated with greater ecosystem resilience and productivity. Therefore, the modern oral environment is likely to be less resilient to perturbations in the form of dietary imbalances or invasion by pathogenic bacterial species. (1)

It’s important to recognize that oral health status is an important determinant of overall health status. If your oral health is poor and your oral microbiome is in a sorry state, then chances are your overall health is also poor, in part because the issues that arise as a result of oral dysbiosis extend far beyond the oral cavity (1). 

The nutritional authorities who issue dietary guidelines for the public fail to fully account for the impact sugars and starches have on our oral health

It’s not surprising that the oral health of the modern man is so poor, seeing as the carbohydrate content of the human diet has surged to unprecedented levels in a very short period of time. Natural selection has never gotten around to adapting our bodies to our novel diets and microbiomes. Not just because the change in diet and microbiome composition has been so sudden, but also because tooth decay and many other oral health problems don’t have a major impact on organismal fitness. This is particularly true when talking about 21st century humans, seeing as we have access to dental care products and have the option of getting our teeth checked at the dentist’s office.

This shouldn’t lead us to neglect the impact that the food we eat has on our oral health though. Regardless of how much we brush and flush, we won’t achieve great oral health if a steady stream of carbohydrate-rich foods enters into our bodies. Unfortunately, the people who develop dietary guidelines for the public seem to largely overlook this fact. They pay little or no attention to the multiple lines of evidence that show that the transition over from traditional dietary practices towards western dietary practices is always accompanied by declining oral health. This has been shown all over the world over the past millennia, as more and more traditional people have been exposed to modern foodstuffs (1, 2, 3, 4, 5, 10).

One of the main problems with the official dietary recommendation that says we should consume a lot of carbohydrates is that it doesn’t take the trillions of microorganisms that colonize our bodies into account. It’s certainly true that it’s wise to consume quite a bit of non-starch polysaccharides and other fibers; however, I very much question the notion that it’s wise to consume a very starch-heavy diet. The fact that the consumption of grains and sugary foods are known to adversely affect oral health and increase one’s risk of developing dental caries should lead us to think twice before we make bread, pasta, and candy a significant part of our diets.

We don’t need thousands of randomized clinical trials to find out what types of foods that agree with our bodies. We can learn a lot simply by examining our evolutionary history and observing how different foods affect our health. The simple fact that our oral health suffers when we eat a lot of grains and sugary foods such as ice cream and cupcakes clearly suggests that we’re not well adapted to eat those types of foods.

Picture: Creative commons picture by feel-the-silence. Some rights reserved.


  1. Undoubtedly what you say is true, but I think the other reason a lot of people have problems with their teeth is they don’t clean them well enough, if at all. There are plenty of people who don’t bother to floss or use a Waterpik, much less brush, until they are in pain and their teeth are literally falling out due to decay. No doubt poor diet and oral neglect go hand in hand to keep the dental industry thriving.

    • Alan Low says:

      Why then, do you imagine early hunter gatherers had full mouths of undecayed teeth without periodontal disease, despite no floss, waterpik or tooth brush?

    • True, Shary!

      The point I’m trying to make with the article is not that oral hygiene isn’t important. Rather, the point I’m trying to make is that no amount of flossing or brushing can fully undo the damage inflicted by a sugary, starchy diet. The primary reason why the typical westerner needs oral care products such as toothpaste and mouthwash to keep his teeth free from caries is that he eat a species-inappropriate, high-carbohydrate diet.

  2. Lynn Wright says:

    Read “Nutrition and Physical Degeneration” by Dr Weston A Price to better understand how diet affects oral health. I cut out grains about four years ago and my dental health has improved greatly. My sister, a carbaholic, is losing her teeth and has many dental problems.

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