Plain carbonated water is not bad for you. It hydrates just as well as flat water, doesn’t weaken your bones, and carries minimal risk to your teeth. Most of the health concerns people associate with “fizzy drinks” actually come from sugars, phosphoric acid, and other additives in sodas, not from the carbon dioxide itself.
That said, carbonation isn’t completely neutral. It can cause bloating, may trigger symptoms if you already have acid reflux, and there’s early evidence it could influence hunger hormones. Here’s what the research actually shows across every concern you’re likely wondering about.
It Hydrates You the Same as Flat Water
Sparkling water is just as hydrating as still water. The carbon dioxide bubbles don’t interfere with your body’s ability to absorb the liquid. The only practical difference is that the fizz can make you feel full faster, which might lead you to drink less in one sitting. During intense exercise, flat water is easier to gulp in large quantities, but for everyday hydration, carbonated water counts equally toward your fluid intake.
The Effect on Your Teeth Is Minimal
When CO2 dissolves in water, it forms a weak acid called carbonic acid. This drops the pH from a neutral 7 (plain water) to roughly 5.25 for a typical sparkling water like Perrier. That sounds concerning until you compare it to other drinks: cranberry juice sits at about 2.5, and sodas fall in a similar range. The American Dental Association considers plain carbonated water “minimally corrosive.”
The key word is “plain.” Flavored sparkling waters often contain citric acid, which pushes the pH lower and makes them more erosive. If you drink a lot of flavored varieties, rinsing with plain water afterward or not sipping continuously throughout the day helps protect your enamel. But unflavored sparkling water on its own is not a meaningful threat to your teeth.
It Doesn’t Weaken Your Bones
The idea that carbonation leaches calcium from your bones is one of the most persistent myths about sparkling water. A study of older women published in the American Journal of Clinical Nutrition measured bone mineral density against carbonated beverage intake and found no association after adjusting for age, weight, calcium intake, exercise, and other lifestyle factors. The conclusion: modest intake of carbonated beverages does not appear to harm bone density.
This myth likely stems from research on cola specifically. Cola contains phosphoric acid, which in large quantities can shift your body’s calcium balance. Plain carbonated water doesn’t contain phosphoric acid, so the concern simply doesn’t apply.
Digestion, Bloating, and Acid Reflux
The most common real complaint about carbonated water is bloating and gas. You’re swallowing dissolved CO2, and as it warms up in your stomach, it expands. This can cause belching, a feeling of fullness, and mild abdominal discomfort, especially if you drink it quickly or in large amounts. For most people this is temporary and harmless.
If you have irritable bowel syndrome, you may be more sensitive to this effect. Research shows that gas production in the gut contributes to the sensation of bloating and stomach rumbling, though interestingly, the actual physical distention of the abdomen appears to involve different mechanisms, like changes in how the diaphragm and abdominal muscles respond, rather than just excess gas.
The picture is more complicated for acid reflux. Some studies have found that carbonated beverages temporarily reduce pressure in the valve between your esophagus and stomach, which could allow acid to creep upward. Cross-sectional data suggests that people with gastroesophageal reflux disease are about twice as likely to consume carbonated beverages as healthy individuals. However, a systematic review noted that while carbonation may cause short-term drops in esophageal pH and increase transient relaxations of that valve, the evidence linking it to actual reflux symptoms is limited. If you already experience heartburn, carbonated water could make it worse. If you don’t, it’s unlikely to cause problems.
One area where carbonated water appears neutral: overall digestion speed. A study measuring gastric emptying found that carbonated water didn’t change how quickly food left the stomach compared to still water.
Carbonation and Hunger Hormones
A small but notable study found that carbonation itself, not sugar, may increase levels of ghrelin, the hormone that signals hunger. In male rats, those drinking carbonated beverages had higher ghrelin levels and ate more than controls. A parallel test in 20 healthy human males showed the same ghrelin spike after drinking carbonated beverages compared to flat alternatives. The researchers suggested that CO2 gas could stimulate the hunger response.
This is a single study with a small human sample, all male, so it’s far from settled science. But if you’ve noticed you feel hungrier after drinking sparkling water, this may be part of the explanation.
Not All Sparkling Drinks Are the Same
The term “CO2 water” covers several different products, and the differences matter:
- Seltzer is just water plus carbon dioxide. No minerals, no additives. This is the cleanest option.
- Club soda is carbonated water with added minerals like sodium bicarbonate and potassium sulfate. A 12-ounce serving contains about 3% of the daily value for sodium, which is trivial for most people but worth noting if you’re on a strict low-sodium diet.
- Sparkling mineral water is naturally carbonated from a spring and contains varying amounts of sodium, magnesium, and calcium depending on the source.
- Tonic water contains sugar (or sweeteners) and quinine. It’s closer to a soft drink than to water and shouldn’t be treated as a health-neutral choice.
The Real Concern Is What’s Added to It
Research linking carbonated beverages to kidney stones, diabetes, and chronic kidney disease consistently points to cola and sugary soft drinks as the culprits, not plain carbonated water. Cola beverages contain phosphoric acid, which promotes urinary changes that favor kidney stone formation. In a randomized trial, men with kidney stones who continued drinking phosphoric acid-containing soft drinks had higher recurrence rates than those who switched to citric acid-based beverages. Noncola carbonated beverages showed no increased risk.
Plain carbonated water contains no phosphoric acid, no sugar, and no caffeine. The carbon dioxide itself, at the levels present in sparkling water, is not linked to kidney damage or stone formation. If you’re choosing between a soda and a sparkling water, the sparkling water is overwhelmingly the better option.