A preliminary crossover study in 20 adults found that unsweetened sparkling water produced a smaller and shorter drop in salivary pH than sugar-sweetened soda. Wajiha Zulfiqar of Purdue University led the trial, which compared regular soda, plain sparkling water, calcium-fortified sparkling water, and still water. Sugar-sweetened soda caused the largest and longest acid shift, with salivary pH remaining significantly lower than water at both 2 and 20 minutes, while unsweetened sparkling water triggered milder, briefer changes.
Why the pH gap between sparkling water and soda matters for daily drinkers
Millions of Americans now reach for unsweetened sparkling water as a routine soda substitute, and the central question for their dental health is straightforward: does carbonation alone push mouth acidity into the danger zone for enamel? The Purdue data suggest it does not, at least not to the same degree as sugar-sweetened soda. Soda drove salivary pH significantly lower than water at both the 2-minute and 20-minute marks, according to conference materials published by the American Society for Nutrition. Unsweetened sparkling water, by contrast, did not produce the same sustained acid environment.
That distinction matters because enamel erosion depends not just on how low pH drops but on how long the acidic window stays open. A brief dip toward mildly acidic territory gives saliva time to remineralize tooth surfaces. A prolonged plunge, the kind soda delivers, can overwhelm that repair cycle. The practical takeaway for people choosing between a can of cola and a bottle of plain seltzer is that the two drinks are not equivalent threats to teeth, even though both contain dissolved carbon dioxide.
A separate hypothesis worth testing in future work asks whether the mineral content of sparkling water, not just the absence of sugar, plays a protective role. If titratable acidity and buffering capacity drive net enamel mineral loss more than the lowest recorded pH alone, then sparkling waters containing calcium and phosphate could produce dissolution rates close to those of plain water over weeks of repeated exposure. The Purdue study included a calcium-fortified sparkling water arm, but the conference summary does not report titratable acidity values or exact mineral concentrations for the beverages tested, leaving that question open.
Primary trial data and earlier lab findings on carbonation and enamel
The Purdue results align with earlier peer-reviewed work. A randomized adolescent crossover trial in 18 participants measured salivary and dental biofilm pH at intervals from 0 to 60 minutes after they consumed a sucrose soft drink, a diet soft drink, carbonated water, and plain water. Sucrose soda drove larger salivary pH reductions than the other beverages. Carbonated water produced a measurable but comparatively modest acid response, and plain water served as the neutral baseline.
Lab-based studies add a layer of caution. Researchers who examined the erosive potential of flavored sparkling waters found that titratable acidity and dissolution varied considerably among products. Flavored varieties, which often contain citric or other organic acids, showed measurable erosive capacity beyond what their pH values alone would predict. That finding separates plain carbonated water from its flavored cousins and warns consumers against assuming all sparkling waters behave identically.
A third study tested carbonated water produced by a home soda carbonator on enamel samples that had been either etched or sealed. The results showed that carbonated tap water can negatively affect enamel surfaces that are already compromised, with microhardness and scanning electron microscopy revealing changes on etched specimens. For people with orthodontic brackets, acid-etched bonding sites, or existing enamel wear, even plain sparkling water may pose a risk that healthy, intact enamel can better withstand.
A separate in vivo study measured pooled plaque and saliva pH at 5, 10, 20, and 30 minutes after participants drank Sprite and modified versions containing fluoride and calcium phosphate. That trial demonstrated that formulation changes can shift oral pH dynamics after consuming a carbonated drink, reinforcing the idea that what is dissolved in the water matters as much as the carbonation itself.
Gaps in the sparkling water evidence and what to watch next
Several questions remain unanswered. The Purdue study enrolled 20 adults and tracked salivary pH over a short window. No direct enamel surface measurements, such as microhardness testing or electron microscopy, were performed on participants’ teeth. All existing evidence about physical enamel damage from carbonated water comes from separate in vitro models, which simulate mouth conditions but cannot fully replicate the protective roles of saliva, the acquired pellicle, and normal chewing.
Duration and pattern of use are also unresolved issues. Most experimental protocols examine a single exposure or a small number of drinks under controlled timing. In the real world, some people sip seltzer throughout the day, effectively extending the time their teeth experience lower pH. Others drink it quickly with meals, when saliva flow is already stimulated and buffering capacity is higher. Without long-term observational or intervention data tracking enamel wear in habitual sparkling water drinkers, clinicians must extrapolate from short-term pH curves and laboratory erosion rates.
Product diversity complicates those extrapolations. “Sparkling water” now spans plain carbonated tap water, mineral waters with naturally high calcium content, flavored seltzers with added acids, and lightly sweetened or juice-blended options that blur the line with soft drinks. The available studies rarely capture this full spectrum. Many focus on a small number of commercial brands or on standardized laboratory formulations that do not match what consumers actually buy. As a result, the risk profile for an unflavored, calcium-rich mineral water may differ substantially from that of a citrus-flavored seltzer, even though both are marketed under the same broad category.
Another gap involves individual susceptibility. People with reduced saliva flow from medications, radiation therapy, or systemic conditions may have a harder time neutralizing even modest acid challenges. Those with extensive restorations, exposed root surfaces, or pre-existing erosive wear may be more vulnerable to incremental damage from any acidic drink, including sparkling water. Current trials generally recruit healthy volunteers with normal salivary function, which may understate the risk in these higher-risk groups.
Future research could address these gaps by combining clinical and laboratory approaches. Longitudinal studies following regular consumers of different carbonated beverages, paired with periodic enamel hardness or optical wear measurements, would clarify whether the short-term pH differences seen between soda and sparkling water translate into meaningful differences in tooth surface loss over years. Parallel in vitro work could test a wider range of commercially relevant formulations, including flavored and mineral-enriched waters, under standardized conditions that approximate typical sipping patterns.
Practical guidance for patients and clinicians
Even with these uncertainties, some pragmatic messages emerge. For patients choosing a carbonated drink, plain unsweetened sparkling water appears substantially less harmful to oral pH than sugar-sweetened soda, and likely less erosive than many flavored soft drinks that layer sugars and organic acids onto carbonation. When sparkling water is consumed, having it with meals, finishing it in a limited time rather than sipping continuously, and alternating with still water can all help limit the duration of acidic exposure.
Clinicians can tailor advice based on individual risk. People with healthy enamel and good saliva flow who mainly drink plain seltzer in short bursts may not need to avoid it. In contrast, patients with active erosion, orthodontic appliances, or dry mouth may benefit from stricter limits on any acidic beverages, including sparkling waters, and from strategies such as rinsing with water afterward or using fluoride products to bolster remineralization. Emphasizing that “sugar-free” does not automatically mean “tooth-neutral” can help patients scrutinize ingredient lists for added acids and sweeteners.
Ultimately, the emerging evidence suggests that carbonation alone is not the primary driver of enamel erosion. What matters more is the combination of sugars, acids, mineral content, and drinking patterns. Unsweetened sparkling water occupies a middle ground: not completely benign, especially for vulnerable teeth, but clearly distinct from sugar-sweetened soda in its impact on salivary pH and likely on long-term enamel health. As more detailed studies appear, guidance can shift from broad generalizations toward more nuanced, product-specific recommendations.
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*This article was researched with the help of AI, with human editors creating the final content.
