Is Carbonated Water Actually Bad for Your Teeth?
“It forms acid!” “The acid is too weak to hurt!” What’s the truth?
Table of Contents
· Carbon dioxide refuses to stay put in the water, unfortunately · Carbonic acid versus tooth enamel · Could the right additives reduce sparkling water damage? · In summary: sparkling water isn’t as bad as soda, but it’s not harmless ∘ Have you heard any recommendations (or fears) about sparkling water?
It’s now the year 2023, and I hope that pretty much everyone is aware that typical soda is not a healthy choice. It’s got no nutrients, there’s no actual lemon or lime in that faux ‘lemon-lime-flavored’ soda, and the insane amounts of dissolved sugar are rotting your teeth, adding pounds to your waistline, and damaging your body’s ability to regulate its blood sugar, contributing to your risk of diabetes.
But what about carbonated water? Sparkling, fizzy beverages that have zero calories, none of the guilt of the sugar-heavy sodas. Are they okay?
I’ll add, as a personal note, I really like sparkling water. I like the way it fizzes on my tongue, like the little bubbles, like how I don’t feel guilty about how many calories I just drank (since it’s zero!). So, going into this article, I’m a little bit biased.
But a good scientist doesn’t let a personal bias distract from the truth. We want clear, peer-reviewed, published evidence to support our answers!
So, what’s the verdict on carbonated water? Good, bad, deadly, surprisingly healthy?
Carbon dioxide refuses to stay put in the water, unfortunately
First, let’s briefly talk about what carbonated water is, and what it does.
Carbonated water, “fizzy water”, seltzer-water, sparkling water — whatever you call it, it’s water that is infused with carbon dioxide gas. You can pack up to 1.5 liters of carbon dioxide gas into 1 liter of water, so you can get it pretty fizzy!
What about other gasses? Most gasses will either spoil the drink (oxygen), make it too flammable (methane), or make it toxic (chlorine). We do occasionally use nitrogen, which is how you get “nitro” cold-brew coffee or beer. The technical term is nitrogenated drinks, and they have a different tasting profile and experience.
Nitrogenated drinks offer a smooth, creamier drinking experience, because the nitrogen forms smaller bubbles and doesn’t alter the flavor of the drink at all, as it’s an inert gas.
Why don’t we have nitrogenated water for sale? A number of reasons:
- Nitrogen gas is more expensive than carbon dioxide, which would make nitrogenated water more expensive.
- Much less nitrogen can be dissolved in water than carbon dioxide, which means you won’t get nearly as many bubbles.
- It’s hard to distribute nitrogenated drinks. Those that are sold, like Guinness beer, actually have a tiny plastic widget that is filled with liquid nitrogen just before the beer is sealed in the can. That takes a lot of extra effort.
- Finally, nitrogen doesn’t react with water, so we don’t get the sweet, acidic flavor that we get with carbonated water.
Back to our good ol’ carbonated water. Carbon dioxide, unlike nitrogen, reacts with water. CO2 + H2O = H2CO3, which is also known as carbonic acid.
That’s right — carbonated water is actually acidic, as you’d see if you were to test it with a pH strip. Carbonic acid converts to bicarbonate, HCO3, and an extra hydrogen ion. Extra hydrogen ions = acid.
That carbonic acid has a taste, as well, which is why sparkling water tastes different from flat water. (If you want to test this, try the following: get a glass of sparkling water and vigorously stir it, then let it sit out a bit. Once all the bubbles are gone, the carbon dioxide has left — but it will still taste different from still water. That taste is due to the carbonic acid left behind in the liquid.) Carbonic acid tastes slightly sour/bitter.
Interestingly, our “sour” taste receptors also can taste the presence of the actual, gaseous, dissolved carbon dioxide! This may have been an evolutionary mechanism to help animals avoid spoiled, fermenting food.
So, to sum up:
- Carbonated/sparkling/fizzy water is made with dissolved carbon dioxide.
- Some of that carbon dioxide leaves as bubbles, but some reacts with the water to form carbonic acid.
- Our taste receptors detect both items; the dissolved carbon dioxide (sour/fizzy), and the carbonic acid (sometimes sour, more commonly described as bitter).
Now, let’s talk health. What’s the danger of that carbonic acid?
Carbonic acid versus tooth enamel
Our tooth enamel, the hard coating that protects the more sensitive inner dentin and pulp of our teeth, is incredibly durable, but it is not totally resistant against acid. It has a critical pH for erosion of 5.5, meaning that any liquid that’s at a 5.5 pH or lower will eat away at the enamel.
(For anyone who hasn’t taken chemistry in a while, pH is a 14-point scale. Pure water is at 7.0, and is neutral. If a liquid’s pH is less than 7, it’s acidic. Higher than 7, and it’s basic. Each number represents a 10-fold increase, so a pH 4.0 acid is 10x as strong as a pH 5.0 acid.)
Even before we touch the carbonic acid, many bottled waters are not at a true neutral pH. A 2022 study in Portugal found that a couple examples of still water (5 of 73) were below pH 5.5.
But the carbonic acid in sparkling water does lower the pH and increases risk of tooth damage. That same study found that 20 out of 32 examples of sparkling water had a pH below 5.5. That means that the majority of sparkling waters are acidic enough to potentially damage our tooth enamel.
Flavoring may make things even worse. Another study looked at the pHs of various flavored waters, and found that all examples on the U.K. market had a pH between 2.75 and 3.35! That’s about as acidic as pure orange juice, and led to tooth enamel damage in lab tests with teeth submerged in the drinks.
And finally, what happens to the teeth themselves?
- Tests of tooth hardness showed that all levels of carbonation led to a loss of hardness. But the more carbonation in the water, the more damage to the teeth.
- Even the lowest level of SodaStream carbonation was enough to reduce the pH below 5.5, leading to dental erosion.
- Sealants can help protect the teeth underneath, but even the sealant can be partially removed by acid.
So despite my love of carbonated water, the evidence is pretty clear that it’s bad for teeth, leading to erosion and reducing the hardness of teeth even in just 15 minutes of exposure.
Can anything be done to alleviate this?
Could the right additives reduce sparkling water damage?
What if we had a booster that helped protect our teeth from sparkling water? Is there some additive that we could add to our carbonated water that would neutralize it so we could enjoy it without risking tooth damage?
One commonly mentioned additive is calcium ions. Carbonic acid is bad for our teeth because it strips calcium away from our teeth; if we put calcium ions into the water, the hope is that the carbonic acid will bind with these ions, not with calcium from our teeth.
This has been shown to work with fruit juices, for example orange juice. One 2022 study found that adding calcium to orange juice did increase its pH and reduce its damaging effect on teeth, for example.
But before we rush to dump calcium into all of our drinks, we should also note that its benefit is limited. The 2018 study linked above also looked at adding calcium to the carbonated water applied to teeth. If the water was only lightly carbonated, the calcium did help reduce the softening/damage of the teeth, but its effect capped out as carbonation increased. Even with calcium added, the high-carbonation water still damaged the teeth.
Perhaps the best move for beverage makers, if they care about helping preserve teeth, would be to add enough calcium to help bring the pH up above the critical 5.5 level, without fully neutralizing all of the carbonic acid. This way, we’d still get some mild level of “fizzy” taste, without damaging our teeth.
But, unfortunately, there isn’t much incentive for beverage companies to make this addition. People aren’t choosing sparkling water for tooth health; they’re choosing them to avoid sugar (which, to be fair, is also bad for teeth).
In summary: sparkling water isn’t as bad as soda, but it’s not harmless
Overall, drinks should likely be viewed on a spectrum. At the bottom are probably hard sodas (that’s right, Mountain Dew will soon be alcoholic!), with the nasty combo of alcohol and huge amounts of sugar. Sugary sodas are also pretty bad.
While plain, flat water is probably the best thing you can drink, sparkling water is only a step or two below it. It’s still acidic, thanks to the carbon dioxide converting to carbonic acid and lowering the liquid’s pH. Most carbonated waters do have a pH that drops below 5.5, the critical level at which the liquid can damage our tooth enamel.
All other things being equal, switching from a sugary soda to carbonated water is a healthier choice. But then, if possible, you should keep transitioning from carbonated water to either very lightly carbonated water, or to plain water.
Ah, life, where all the enjoyable things seem to harm us! But the relative risk of carbonated water is pretty small. Even the American Heart Association recommends it over sugar-sweetened beverages. As long as you’re not drinking it constantly (maybe try to stick to a single can per day), you’ll do less damage to your teeth than you would from most other beverage choices.
Have you heard any recommendations (or fears) about sparkling water?
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