Evolutionary Association, Chapter 10: Dental Health

How did humanity actually manage to make it all the way to universally available mint-flavoured toothpaste without everyone’s teeth rotting away in early childhood?

And what exactly is the difference between apples, bread, and candy?

The Dietary Change

With the arrival of agriculture and the deliberate breeding of plant varieties for “more yield”, human nutrition changed massively - but modern dental hygiene and dentistry were developed only very recently, and became rather badly needed along the way.

With industrialisation and globalisation, worldwide transport, unbroken cold chains and preservation methods, many foods are available constantly - not only everywhere, but entirely independently of any season. The dietary guidelines do their bit: they recommend a carbohydrate-rich diet - over 50% of energy should please come from carbohydrates. And carbohydrates are what we will look at here in particular - above all those that can already be broken down by enzymes and microorganisms present in the mouth.

There are in fact two broad periods in human history for which an expansion of the caries-promoting microbiome can be demonstrated⁽¹⁾.

The Phenomenon

Despite modern dentistry, dental floss, toothpaste, advice on dental care and professional cleaning, dental health has suffered badly, especially since the 20th century, and dentistry is needed as a repair shop.

Both caries and periodontitis are problems everyone knows. To head off major repairs, German health insurers require an unbroken record of annual check-ups: it lowers the share of the cost patients have to pay towards dentures, and it is meant to encourage regular visits to the dentist.

The prevention instructions, by contrast, come down to: “brush your teeth after eating” and “mind the gap” (e.g. take care of the gaps between them as well).

The Biochemical Association

I hinted at it above: the dietary guidelines go “all in” on carbohydrates - something I have ranted about passionately in many articles on butterbei.de. People need energy, the guidelines recommend restricting fat, which leaves carbohydrates as an all but unavoidable source of it. Despite every drawback that comes with them (see also: all articles about insulin, and the simulator in particular) for metabolism, hormone balance and the tendency to put on weight, we are supposed to take in more than 50% of our energy in this form.

Many people will have tried chewing a piece of bread for a long time, paying close attention to how the taste changes: it gets sweeter and sweeter. That is because saliva already contains enzymes which break up the starch in the bread and release smaller sugar molecules (maltose, for example).

As we already know, the difference between sweets and bread is fairly negligible: leaving taste aside, the effect on the organism is very similar. But there is no need to demonise bread quite that much:

The Deutsche Gesellschaft für Ernährung - German Nutritional Society, a largely government funded NGO, designated as appointed authority on nutritional matters itself explicitly recommends a higher weekly limit for sugar (350 g) than for meat (300 g) in its guidelines⁽²⁾ - and that sugar figure does not even count foods such as fruit, which contain it naturally.

The body has several microbiomes, and any treatment of a microbiome always sounds as though there were “the one good one” - in reality it varies a great deal between individuals and depends heavily on how it is “fed”.

The usual carbohydrate-rich diet gives bacteria that ferment sugar a great deal to live on - many people already know the connection: some of these bacteria, sitting in films on the teeth, feed on sugar and excrete acids that attack the enamel. The result of this - criminally simplified - mechanism is: caries⁽³⁾.

Normally saliva buffers that acid - but effectively only between meals. If those come too often, or last too long (sweets, or snacks stretched across a feature film), the effect falls off sharply.

Even someone who explicitly avoids sweet things, but otherwise eats according to the guidelines, gives these bacteria plenty to feed on: the bread-chewing experiment described above demonstrates it. Sugar is released immediately - swallowing quickly without chewing does not help: starch sticks to the teeth, where the enzymes can break it down. Our sense of taste does not register the sugar straight away, but it is there from the very first moment.

How can I change my oral microbiome?

The microbiome depends on what it is fed. Change the diet and you change the composition of the microbiome (including further down the body - see the articles about fibre here, although in this article, for once, I am not going to beat on fibre yet again).

Anyone who reads the studies in the footnotes will notice: fermentable carbohydrates are the problem. Avoid them and you will change your own oral microbiome automatically - simply because the sugar-fermenting, caries-causing bacteria get fed less.

And for anyone whose mind went to brushing instead: an interesting study from 2009⁽⁴⁾ looked at 10 people who did not brush their teeth at all during four weeks on a stone-age diet. The result: slightly more plaque, but decreasing gum bleeding.

But why ‘only now’?

Why have dental problems piled up only in the recent past, when humanity has had grain and other starchy foods available for so very much longer?

First of all: caries is not a new phenomenon. It is detectable as far back as 15,000 years ago⁽⁵⁾ and is attributed to the acorns of the day - a source of carbohydrate available seasonally and locally well before agriculture arrived - and in that case at an intensity similar to today’s. What is described is an occurrence limited in time and place, which nonetheless precedes the introduction of agriculture. Apart from its closing sentence, the paper offers nothing on the age or the general state of health of these people - but we can assume that badly decayed teeth were not exactly life-extending before modern dentistry was available.

The amount, and the constant availability, of (fermentable) carbohydrates do make a difference: when the dietary guidelines appeared, so did the advice to fit 3 snacks in between the 3 meals a day - but never the advice to brush your teeth six times a day as well. Not only does insulin stay permanently elevated that way (and lead to the problems discussed elsewhere here), the sugar-loving bacteria in the mouth are fed generously too: they also get a fresh delivery every few hours.

In the paper by Adler et al.⁽¹⁾ mentioned earlier, the Neolithic (roughly: the introduction of agriculture) and the availability of industrial sugar are both clearly detectable as steps up in the caries-causing microbiome.

Another paper⁽⁶⁾ points to the period in the last century in which the foundations of today’s carbohydrate-heavy dietary guidelines were laid, and takes the position - in the abstract already - that dental diseases are systemic rather than a locally confined matter of the body.

Sounds as though intermittent fasting or a low-carb diet ought to be a popular preventive instrument among dentists too (though it might spoil their business). A low-carbohydrate diet in particular sounds like a remarkably effective way to reduce the sugar supply to the caries-causing bacteria, while intermittent fasting “only” changes the time available to them. (Hint: You can even combine both)

What does dental health tell us about our diet?

Without teeth, eating is - understandably - difficult. In evolutionary terms we depend on healthy teeth. Which raises the (rhetorical) question of whether a diet that has a massive negative effect on dental health can be regarded as species-appropriate.

Today we have ways of repairing the damage, but they effectively mask the actual biochemical signals. As we have seen in other articles on butterbei.de, sugar and carbohydrates have negative effects everywhere in the body when they are present in excess.

The teeth are an early and clearly visible alarm - one we mute rather than respond to.

We wage the war on caries with fluoride, ultrasound and dental floss, while delivering fresh ammunition to the enemy several times a day.