Carbonation isn’t as harmful as many people assume, but it does have real effects on your body worth knowing about. The dissolved carbon dioxide in fizzy drinks creates carbonic acid, lowers the pH of the beverage, and introduces gas into your digestive system. Whether that matters depends largely on what else is in the drink, how much you consume, and whether you have certain preexisting conditions like acid reflux or irritable bowel syndrome.
Carbonation and Your Teeth
The most concrete concern with carbonation is its effect on tooth enamel. When carbon dioxide dissolves in water, it forms carbonic acid, dropping the pH. Plain carbonated water has an average pH of about 4.5, which sits below the 5.5 threshold where tooth enamel begins to demineralize. That sounds alarming, but the reality is more nuanced. The critical pH for enamel erosion isn’t a fixed number. It shifts depending on the calcium and phosphate already present in the liquid, so the same pH can be more or less damaging depending on what’s dissolved in it.
Flavored sparkling waters are a bigger concern. A 2016 report in the Journal of the American Dental Association found that flavored varieties generally have a pH between 3.0 and 4.0, which puts them closer to the acidity of orange juice. The lower pH comes primarily from the carbonation process itself rather than added flavorings or citric acid, though those ingredients can push acidity even further. Plain seltzer is mildly acidic; citrus-flavored seltzer is noticeably more so.
For context, plain carbonated water is far less erosive than sodas, energy drinks, or fruit juices. Sipping it throughout the day does expose your enamel to a mildly acidic environment for longer, but drinking it with meals or finishing a glass in a reasonable timeframe limits that exposure significantly.
Acid Reflux and Esophageal Pressure
If you deal with heartburn or gastroesophageal reflux, carbonation can genuinely make things worse, and the mechanism is well documented. A study published in the Journal of Gastrointestinal Surgery found that all carbonated beverages (not just sodas) reduced lower esophageal sphincter pressure by 20 to 50% for a sustained period of about 20 minutes. Tap water produced no such effect.
Your lower esophageal sphincter is the muscular valve between your esophagus and stomach. When its pressure drops, stomach acid can escape upward, causing that familiar burning sensation. In 62% of subjects in the study, the reduction was severe enough that the sphincter reached a level normally considered diagnostic of incompetence, meaning it was functionally failing to keep the stomach sealed. This is one area where the evidence is clear: carbonation relaxes a valve that should stay tight, and people prone to reflux will likely notice the consequences.
Bloating and Digestive Discomfort
Carbonated drinks introduce carbon dioxide gas directly into your stomach, which can stretch the stomach and intestinal walls. For most people, this produces a temporary feeling of fullness or mild bloating that resolves quickly. For people with irritable bowel syndrome, however, the effect can be more pronounced. Clinical guidelines for IBS management recommend reducing intake of fizzy drinks, and the Monash University FODMAP team notes that stomach and intestinal distension from the gas is the likely mechanism behind symptom flare-ups in sensitive individuals.
The evidence linking carbonation to digestive problems in otherwise healthy people is thin. Most of the discomfort comes down to gas volume. If you drink large amounts of sparkling water quickly, you’ll feel more bloated than if you sip slowly. The gas has to go somewhere, which usually means belching or passing through the intestines.
Carbonation May Increase Hunger
One of the more surprising findings in carbonation research involves the hunger hormone ghrelin. A 2017 study tested both rats and humans. Rats consuming carbonated beverages over roughly a year gained weight faster than rats drinking the same beverages with the carbonation removed, or plain water. The carbonated-beverage rats ate more food, and their stomachs produced higher levels of ghrelin.
In a parallel human trial, 20 healthy young men showed elevated ghrelin levels in their blood after drinking carbonated beverages compared to flat controls. The researchers concluded that the carbon dioxide gas itself, not the sugar or other ingredients, triggered the ghrelin release and stimulated appetite. This was a small study and the human arm was short-term, but it raises a plausible concern: if you’re trying to manage your weight, fizzy drinks of any kind might subtly nudge you toward eating more.
Bones Are Mostly in the Clear
The idea that carbonated drinks weaken bones is one of the most persistent health claims around fizzy beverages, but the evidence points to a more specific culprit. A clinical trial published in the British Journal of Nutrition compared postmenopausal women drinking about a quart of carbonated mineral water daily with women drinking the same amount of still mineral water. After eight weeks, blood and urine markers for bone turnover showed no difference between the two groups. Carbonated water, on its own, does not appear to contribute to osteoporosis or fracture risk.
Cola drinks are a different story. Research has found that cola intake is associated with lower bone mineral density at the hip in women, with more cola correlating to lower density. But non-cola carbonated drinks showed no such association. The likely explanation isn’t the bubbles. It’s the caffeine in colas and the broader dietary pattern: people who drink a lot of soda tend to drink less milk and fewer calcium-rich beverages. The displacement of nutritious drinks, rather than any direct effect of carbonation, is probably what hurts bone health.
Hydration Isn’t Affected
Some people worry that sparkling water doesn’t hydrate as well as still water. It does. In a controlled study, participants drank a liter of either regular water, sparkling water, or another beverage, and researchers measured urine output four hours later. There was no difference in hydration status between the carbonated water group and the still water group. If you prefer sparkling water and it helps you drink more fluids overall, it’s doing its job.
What Actually Matters
The real-world harm of carbonation depends almost entirely on context. Plain sparkling water is mildly acidic but far less erosive than juice or soda. It doesn’t leach calcium from your bones or dehydrate you. It does relax your esophageal sphincter, which matters if you have reflux. It may increase hunger signals, which matters if you’re watching your calorie intake. And it can worsen bloating if you have IBS or a sensitive gut.
Most of the health problems historically blamed on “carbonation” actually trace back to what rides alongside the bubbles: sugar, phosphoric acid, caffeine, and citric acid. A can of cola and a glass of sparkling water both contain carbon dioxide, but their health profiles are worlds apart. If you’re drinking plain or lightly flavored sparkling water and you don’t have reflux or IBS, the carbonation itself poses minimal risk.