Is sparkling water bad for you? What the evidence shows

For most people, plain sparkling water is not bad for you. It hydrates about as well as still water, and its weak carbonic acid makes it far less corrosive to teeth than fruit juice or soft drinks. The cautions that survive scrutiny are narrow and specific: flavoured fizzy waters carry added acid that can erode enamel [s1], and the beverage that damages bone in the data is cola, not carbonation [s2].

What "sparkling" actually is

Carbonating water dissolves carbon dioxide into it, which forms carbonic acid and lowers the pH below that of still water. That is the whole basis of the worry — an acidic drink, sipped through the day, in contact with tooth enamel. The question is whether the acidity of plain carbonated water is anywhere near the level that erodes teeth, and whether carbonation carries any of the other harms attributed to fizzy drinks. On the three claims that come up most — teeth, bones and hydration — the evidence separates plain sparkling water from the sugary, acidic drinks it is often lumped in with.

Teeth: the flavour is the problem, not the fizz

A UK laboratory study measured the pH, titratable acidity and in-vitro erosive potential of a range of flavoured sparkling waters and found reason for caution. All of them showed appreciable titratable acidity (0.344 to 0.663 mmol) and low pH (2.74 to 3.34), and in a hydroxyapatite dissolution assay all demonstrated erosive potential of 89 to 143 percent relative to pure orange juice, an established erosive drink [s1]. Exposing extracted human teeth to the flavoured waters produced surface changes consistent with erosion [s1]. The authors' conclusion is the useful part: flavoured sparkling waters "should be considered as potentially erosive" and treated as acidic drinks rather than as water with flavouring [s1].

Plain carbonated water is a different object. The same paper notes that the wide-scale consumption of bottled waters "is unlikely to contribute significantly to erosion," and set out to study the flavoured products precisely because their role was unclear [s1]. The added citric or other fruit acids in flavoured versions, not the carbonation, drive the erosive potential. A can of plain sparkling water is mildly acidic; a flavoured one behaves more like juice.

Bones: cola is implicated, other fizz is not

The claim that "carbonated drinks weaken bones" traces largely to one well-known dataset, and it does not say what it is often reported to say. In the Framingham Osteoporosis Study, bone mineral density was measured at the spine and three hip sites in 1,413 women and 1,125 men [s2]. Cola intake was associated with significantly lower bone density at each hip site in women: those drinking cola daily had mean bone density 3.7 percent lower at the femoral neck and 5.4 percent lower at Ward's area than those consuming less than one serving a month [s2].

The result that matters for sparkling water is the negative one. "No significant relations between noncola carbonated beverage consumption and BMD were observed" [s2]. The investigators attribute the cola signal to phosphoric acid and caffeine, ingredients specific to cola and absent from plain sparkling water [s2]. Carbonation itself was not the culprit. This is observational data, and the authors called for confirmation, but as a basis for fearing plain fizzy water it points the other way.

Hydration: as good as still water

The idea that carbonated water is somehow less hydrating does not hold up. A randomised trial developed a "beverage hydration index" by having 72 euhydrated men drink one litre of still water or another beverage and measuring urine output over the next four hours [s3]. Cumulative urine output after sparkling water was not different from the response to still water [s3]. Only drinks with more retained content — an oral rehydration solution and milk — beat plain water, with beverage hydration indices around 1.5 [s3]. Sparkling water sat with the ordinary drinks, meaning it replaces fluid as effectively as the still water it is compared against.

What is left of the worry

Once teeth, bones and hydration are separated out, the residual concerns about plain sparkling water are small and mechanical rather than disease-level. Carbonation introduces gas, which some people find causes belching or a sense of fullness — a comfort issue, not a documented harm. The genuine cautions the evidence supports are that flavoured fizzy waters should be treated as acidic drinks around teeth [s1], and that the beverage tied to lower bone density is cola specifically [s2]. If a sparkling water is unsweetened and unflavoured, the case against it is thin. The drinks worth more caution are the sugary and acidic ones it is easy to confuse it with — the same added sugars and fruit-based drinks that carry their own metabolic and dental risks, and the enamel wear that acidic exposure causes over time. On bone density, the evidence indicts cola, not fizz.

This article is informational and is not medical advice.

Sources

• The erosive potential of flavoured sparkling water drinks — International Journal of Paediatric Dentistry, 2007
• Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The Framingham Osteoporosis Study — The American Journal of Clinical Nutrition, 2006
• A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index — The American Journal of Clinical Nutrition, 2016