I've often heard and read that soda causes tooth decay; most often the reason involves the sugars present in the soda being converted into acids which wear out the enamel.

I'm curious if there is anything in a soda that doesn't contain sugar, such as one that uses aspartame as a sweetener, that would cause tooth decay.

An example of the claim cited in the first paragraph:

MILLIONS of weight-conscious consumers believe it is a healthy choice: low in kilojoules and sugar-free.

But diet cola can make you fat and rot your teeth, according to new research.

Diet cola can 'make you fat and rot your teeth'

  • 4
    I think at least diet coke is also quite acidic, and that acid is certainly not beneficial for your teeth (since I have no info on how much damage it causes I'm posting this as a comment).
    – johanvdw
    Sep 16, 2011 at 21:08
  • related: skeptics.stackexchange.com/questions/2523/…
    – Sklivvz
    Sep 16, 2011 at 21:30
  • 1
    I wonder if carbonation itself has any damaging effect on teeth - bursting bubbles are a source of damage to propellers through cavitation. It seems that the source of bubbles is very different, however.
    – Jonathan
    Sep 16, 2011 at 23:15
  • @Jonathan Cavitation is no problem in soda. The physical forces by carbonate will not harm your teeth. The acid in fact could, you can actually feel it. Your teeth get a little bit soft which is felt like they get a little bit sticky. That's why one should let half of an hour pass between drinking acidic drinks like coke or juice and brushing ones teeth. If you don't do it you will grain away more of the top layer of your teeth with the toothpaste.
    – Darokthar
    Sep 17, 2011 at 7:46
  • @zzzzBov I think I remember, that diet coke could have an effect on diabetes. Because the body gets the signal that sugar is on it's way (because it is sweet) but it never gets delivered. Therefore diet drinks are probably not that good. But I can't find the source.
    – Darokthar
    Sep 17, 2011 at 7:48

2 Answers 2


Summary: Diet drinks are less acidic, but still a problem for dental erosion.

Acids can cause erosion of teeth. Saliva acts as a buffer to prevent it. Saliva is more effective against milder acids. [Ref: Wikipedia]

The bubbles in fizzy drinks (a.k.a. soda, pop, soda water, etc.) is carbon dioxide (CO2) When carbon dioxide is dissolved in water, it spontaneously interconverts with carbonic acid, H2CO3. [Ref: Wikipedia]

So, without any additives, plain carbonated water is acidic, with a pH between 3 and 4. [Ref: Wikipedia]

Diet sodas contain phosphoric acid as well, but remain milder acids than the full-sugar versions. [Ref which puts Diet Coke at ph 3.39 versus Coke Classic at 2.53.]

Note: I have stooped to Wikipedia for my references, because it is just confirming high school science, rather than addressing any controversial topic.

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    In light of carbonated water being acidic, but not detrimental to teeth, I think this answer could use the mention that most diet drinks lack the calcium that prevents the acid from affecting teeth. Reading this answer, there is no reason to believe carbonated water would not hurt teeth. skeptics.stackexchange.com/questions/22890/…
    – Spork
    Aug 19, 2014 at 8:48
  • The general impression I take from this answer is that diet drinks are bad, just not as bad as sugary ones. But the answer lacks useful detail. For example is diet-drink related tooth erosion notable if the volume consumed is not excessive? For an equivalent volume consumed for diet or sugary drinks, how many cavities would be expected? I have no idea from te answer whether diet drinks are 10% better or 90% better.
    – matt_black
    Sep 2, 2021 at 20:14
  • @matt_black: This question - and this answer - both date back to the "Wild West" days of Skeptics.SE, before we had narrowed down the scope and community standards. I agree this answer is missing an overall reference showing empirically that all these jigsaw pieces fit together. OTOH, it does plug a gap in the OP's understanding, by showing that there is more than one source of tooth decay. I don't really know what to do about it now.
    – Oddthinking
    Sep 4, 2021 at 1:36
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    @Oddthinking Fair point. presumably that's why the algorithm sometimes bubbles them back to the top so new eyes can see them and new readers improve them.
    – matt_black
    Sep 4, 2021 at 9:26

The acidity of the "soda" is the issue that contributes a lot to tooth decay. The can says "Phosphoric Acid." See http://en.wikipedia.org/wiki/Phosphoric_acid

Phosphoric Acid may also reduce bone density.

Carbonic Acid is also present ( http://en.wikipedia.org/wiki/Carbonic_acid).

I find Wikipedia useful as television has shown us most people might not be smarter than a 5th grader :)


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