Drinking carbonated beverages introduces carbon dioxide gas into your digestive system, which causes a predictable chain of events: the gas warms up, expands, and either gets absorbed or comes back up as a burp. For most people, this is completely harmless. But the effects on your teeth, stomach, appetite, and hydration are worth understanding, especially if you drink sparkling water or soda regularly.
What Happens to the Gas in Your Stomach
Carbon dioxide is dissolved into liquid under pressure. The moment you swallow it, your body’s warmth causes that dissolved gas to rapidly convert back into its gaseous form, expanding inside your stomach. If the pressure builds enough, it triggers a reflex in the upper part of your stomach that produces a belch. That’s your body’s release valve.
If you drink on an empty stomach, most of the liquid passes quickly into the small intestine, where the carbon dioxide converts into bicarbonate, a harmless compound your body already produces naturally. Symptoms like uncomfortable fullness or bloating typically only appear when you drink more than about 300 ml (roughly 10 ounces) of a carbonated beverage in one sitting. Below that threshold, most people won’t notice much beyond a burp or two.
Carbonation and Hunger
One surprising effect: carbonation may actually make you hungrier. A study involving both rats and 20 healthy human males found that drinking carbonated beverages raised levels of ghrelin, the hormone that signals hunger to your brain. The rats drinking carbonated drinks ate more food than those given flat beverages, and the human participants showed the same spike in ghrelin after drinking something fizzy. This suggests that the carbon dioxide itself, not sugar or other ingredients, plays a role in stimulating appetite. If you’ve ever noticed you feel hungrier after a sparkling water, you’re not imagining it.
Effects on Your Teeth
Carbonation makes water more acidic. Plain sparkling water typically falls between pH 4.18 and 5.87, and tooth enamel starts dissolving at pH 5.5. That means some carbonated waters sit right at or below the threshold where enamel erosion begins.
Higher carbonation levels cause more enamel damage. In lab testing, heavily carbonated water produced significantly greater reductions in enamel hardness compared to lightly carbonated water. Adding calcium to the water helped offset this effect, which is one reason mineral-rich sparkling waters are a better choice for your teeth than plain seltzer. Still, the erosion from unflavored sparkling water is far less severe than from sodas, citrus juices, or sports drinks, which are much more acidic. If you’re sipping sparkling water throughout the day, using a straw or rinsing with plain water afterward reduces the acid’s contact time with your teeth.
Hydration Stays the Same
Sparkling water hydrates you just as well as still water. Researchers developed a beverage hydration index to compare how different drinks affect your body’s water balance, and carbonated water performed identically to flat water. The bubbles don’t cause you to lose fluid faster or absorb less. The only practical difference is that carbonation can make you feel full sooner, so you might drink less volume in one sitting compared to still water. During intense exercise, that reduced intake could matter, making flat water the easier choice when you need to rehydrate quickly.
Bloating and Digestive Sensitivity
For people with irritable bowel syndrome, carbonated drinks can worsen symptoms. The fizzy effect that happens in your mouth continues through your GI tract, producing gas that contributes to bloating, distension, and abdominal discomfort. Johns Hopkins Medicine lists carbonated beverages among the drinks people with IBS should avoid, recommending still water instead. Even without IBS, some people are simply more sensitive to the gas expansion, particularly those prone to bloating or excessive belching.
Acid Reflux: Less Risky Than You’d Think
Carbonation does cause a brief dip in the pH inside your esophagus and can temporarily relax the muscular valve between your esophagus and stomach. That sounds like a recipe for acid reflux, but the evidence doesn’t support a strong connection. A systematic review of the available research found no direct evidence that carbonated beverages cause or worsen gastroesophageal reflux disease. They haven’t been linked to esophageal damage or increased cancer risk either. If you already experience reflux, carbonation might trigger occasional discomfort, but it’s not a proven cause of the condition itself.
Bone Density Is Not Affected
The idea that carbonation weakens your bones comes from studies on cola specifically. The well-known Framingham Osteoporosis Study found decreased bone density in the hips of older women who drank cola, but women in the same study who drank non-cola carbonated beverages showed no increased bone loss. The culprit in cola appears to be phosphoric acid, an ingredient specific to cola drinks, not the carbonation. Plain sparkling water, seltzer, and club soda do not pull calcium from your bones or interfere with bone mineral density.
Sugary Versus Plain Carbonated Drinks
Everything above applies to plain carbonated water. When sugar enters the picture, the health effects change substantially. Sugary sodas combine carbonation’s mild acidity with high sugar content, dramatically increasing the risk of tooth decay, weight gain, and metabolic problems. Flavored sparkling waters with added citric acid are also more erosive to enamel than plain sparkling water because citric acid is stronger than carbonic acid alone. If you’re choosing between sparkling water and soda, the sparkling water is a far better option. If you’re choosing between sparkling and still water for all-day sipping, still water is gentler on your teeth.