Coca-ColaCoke is perhaps the worst possible thing that you can do to your teeth -- shy of getting into a fight with a motorcycle gang -- and it's one of those rare occasions where brushing your teeth afterwards does more harm than good. The reason why is right there in the ingredients label; phosphoric acid. That sounds like an industrial chemical instead of a food ingredient, and the fact of the matter is that it is indeed an industrial chemical.
When you drink phosphoric acid, a lot of things happen. Things deep in your intestines and in your bones and all over your body; my nutritionist tells me that a can of cola is essentially an anti-multivitamin. It actually causes your body to urinate out a whole pile of vitamins and minerals that it should otherwise have kept and used. That lack of micronutrients really does affect the health of your teeth in the long run -- but it's nothing compared to the short-term impact.
The short-term impact is that the phosphoric acid severely weakens your enamel, especially if you keep the drink in your mouth for any considerable period of time. That's why brushing your teeth after you drink Coke is a bad idea. Even a medium-hard toothbrush will literally scrub the weakened enamel away, and leave you in dire need of Dr. Johnson.
Now, we do have to put a bit of a lid on the hysteria, because we've done the research; cola will not, in fact, dissolve a tooth overnight. It takes a few weeks, and fresh-squeezed orange juice will actually do the job faster. But that doesn't mean it's necessarily safe to drink regularly if you want to avoid a trip to our office.
If you must drink a sugary, manly, bubbly drink this summer, we encourage you to check the label. If it lists any kind of acid that isn't citric, you should probably switch drinks. According to one study, root beer is generally best for your teeth if you must have a soft drink.