Carbonated drinks can worsen acid reflux, and the evidence is strong enough that the American College of Gastroenterology lists avoiding them as a recommended lifestyle change for people with GERD. The carbonation itself is the core problem: released carbon dioxide gas expands in your stomach, weakening the muscular valve that keeps stomach acid from traveling upward into your esophagus.
That said, not all carbonated drinks carry equal risk. The type you’re drinking, when you drink it, and how much matters quite a bit.
How Carbonation Triggers Reflux
At the bottom of your esophagus sits a ring of muscle called the lower esophageal sphincter (LES). It opens to let food into your stomach and closes to keep acid from splashing back up. Carbon dioxide gas from any carbonated drink expands inside your stomach, stretching it. That stretch weakens the sphincter.
Research measuring this effect found that carbonated beverages reduce the sphincter’s holding pressure by 30 to 50%, and that this reduction lasts around 20 minutes after drinking. In 62% of cases, the weakening was severe enough that the sphincter reached a level doctors would classify as incompetent, meaning it essentially stops doing its job. With the valve compromised, stomach acid has a much easier path into the esophagus, producing that familiar burning sensation.
The gas also triggers belching. When carbon dioxide builds enough pressure in the upper part of your stomach, your body reflexively opens the sphincter to release it. Each belch creates an opportunity for acid to ride along with the escaping gas. So the carbonation hits you twice: it weakens the valve passively through stomach stretching and opens it actively through belching.
Why Soda Is Worse Than Sparkling Water
All carbonated drinks share the gas problem, but sodas pile on additional reflux triggers. Cola-style sodas like Coca-Cola and Pepsi have a pH around 2.3 to 2.4, making them extremely acidic on their own. For context, stomach acid sits around pH 1.5 to 3.5, so drinking a cola is essentially adding more acid to the mix.
Plain sparkling mineral water is far less acidic. San Pellegrino measures at a pH of about 5.0, and club soda comes in around 5.2. These are close to the pH of plain tap water and unlikely to irritate the esophagus on their own. Flavored sparkling waters fall somewhere in between: fruit-flavored varieties can dip to a pH of 3.0 to 3.7, firmly in the acidic range.
Caffeine, present in most colas and some other sodas, independently relaxes the esophageal sphincter. Sugar may also play a role in worsening GERD symptoms, though the exact mechanism is still being studied. The combination of carbonation, high acidity, caffeine, and sugar makes regular soda one of the worst beverage choices for anyone dealing with reflux.
Timing and Portions Matter
When you drink a carbonated beverage can be just as important as what you drink. Consuming soft drinks between meals appears to be particularly problematic. Each time you eat or drink something that stimulates acid production, your stomach creates a layer of highly concentrated acid that sits on top of the food. This “acid pocket” is the main source of reflux episodes. Snacking or sipping soft drinks between meals forces the stomach to re-create this acid pocket repeatedly throughout the day, multiplying the chances for acid to escape upward.
Drinking carbonated beverages close to bedtime compounds the issue further. Lying down removes gravity’s help in keeping acid in your stomach, so the weakened sphincter has even less backup. If you’re going to have a sparkling drink at all, having it with a meal (rather than between meals or before bed) and keeping the portion moderate gives your body the best chance of handling the gas without significant reflux.
Plain Sparkling Water: A Gray Area
If you love sparkling water and have mild or occasional reflux, the picture is less clear-cut than it is for soda. Plain carbonated water has near-neutral acidity, no caffeine, and no sugar. Its only reflux trigger is the gas itself. Some people with mild symptoms tolerate it fine, while others notice it consistently sets off heartburn or belching.
Gastroenterologists at UChicago Medicine recommend that patients with active GERD or frequent gas who are drinking mostly carbonated water switch to still water instead. The reasoning is straightforward: even without the added acidity of soda, the mechanical effect of gas stretching the stomach and weakening the sphincter still applies. If you’re unsure whether sparkling water is a problem for you specifically, cutting it out for two to three weeks and tracking your symptoms gives you a personal answer that population-level studies can’t.
What to Drink Instead
Still water is the safest option. It hydrates without gas, acidity, caffeine, or sugar. Beyond water, non-citrus herbal teas served at a warm (not hot) temperature are generally well tolerated. Low-fat or plant-based milk can temporarily buffer stomach acid, though high-fat dairy may slow digestion and worsen reflux in some people.
If giving up carbonation entirely feels unrealistic, a few adjustments can reduce your risk. Choose plain sparkling water over flavored varieties or soda. Pour it into a glass and let some of the fizz dissipate before drinking. Keep servings small, stick to mealtimes rather than sipping throughout the day, and stay upright for at least two to three hours afterward. These steps won’t eliminate the gas effect entirely, but they meaningfully reduce how much your sphincter has to cope with at any given moment.