More Sugary Questions
Confusion slightly reduced, still confused though
Sugary Things I’m Fairly Confident About
After a bit of research, it looks like it's sucrose specifically (a glucose molecule linked to a fructose molecule by an oxygen bond to make a disaccharide), combined with a bacterium streptococcus mutans that may be recently evolved, that screws up teeth.
Although bacteria can turn all sugars into acids in your mouth, only streptococcus mutans can make plaque (a polysaccharide, a sort of sugar-based plastic!), and it can only make it out of sugar.
The plaque gives the various bacteria a way to stick to the teeth, and somewhere to hide, and in the plaque, the acid levels get high enough to damage (demineralize) teeth.
So we don't have to explain why we like the taste of most sugars, they're just lots of lovely calories, and your teeth are fine, because the bit of acid that they turn into in your mouth does no harm and washes away.
So lactose in milk is fine on its own. Honey, a mix of glucose and fructose, but mostly not bonded into the disaccharide, is fine.
Fructose in fruit is also fine, except….
A lot of fruits have sucrose in them too.
To get rotten teeth, you need both sucrose and streptococcus mutans.
It looks like sucrose is fine as a source of calories, almost all animals have an enzyme (sucrase) that splits it, so it turns speedily into glucose and fructose in the gut.
That almost universal sucrase enzyme shows that sucrose has been in the diet of most creatures for a long time.
Industrial sugar production from the (newly bred) sugar beet appears to have started in about 1800 in Europe, but apparently in China and India it’s been going on for a long time. Alexander the Great’s men brought sugar cane back, but luckily for classical teeth it doesn’t grow so well in Europe.
Things like beetroot definitely grow in Europe, and are a traditional food. That’s where the sugar beet came from. Beetroots have got a fair bit of sucrose in them.
Sugary Questions Remain
Why don’t fruit-eating animals (like most great apes!) get tooth decay?
Any significant source of sucrose should allow plaque to build up, and absent some way of cleaning it off, the bacteria in the plaque should then turn any sugar, or even any carbohydrate, into tooth-destroying strong acid.
This cannot be. Tooth decay in the absence of antibiotics would kill by infection if not directly by starvation.
Is high-fructose corn syrup / glucose-fructose syrup, being chemically more like honey than like sucrose/table sugar, actually a better thing to eat/drink than sucrose? (from a tooth point of view ; nutritionally I’d be surprised if there was much difference).
Was newly-refined (from beet)/imported (from cane) sucrose (in combination with s.mutans) the first health-destroying frankenfood?
Why haven't the British evolved to dislike sugar over the four hundred years it's been destroying our teeth?
Did European ancestral populations have any access to it?
Beetroot is a traditional European crop, so probably Europeans have been eating sucrose for a long time. That makes the paradox even tighter.
When did streptococcus mutans evolve its plastic-from-sucrose trick?
If it's as late as in the last couple of hundred years, how did the Elizabethans get their black teeth?
If it’s as early as thousands or millions of years ago, have Indians and Chinese had rotten teeth since forever?
And then we’ve got the original question back, how come Indians and Chinese don’t have defenses against tooth decay? Just disliking the taste of sucrose or foods high in sucrose would do.
As an emergency fix, breaking the sucrase enzyme would do. Sucrose would then make you pretty ill as it fermented in your stomach, and you’d quickly learn to avoid it. That could happen and go to fixation in historical time.
And why don’t dentists tell the sweet-toothed to use honey instead of sugar?
Honey ice-cream sounds lovely, and I don’t even like sugar that much!
More research is needed.