Carbonated water does appear to help with constipation, at least modestly. In a double-blind randomized trial, people with functional constipation who drank carbonated water for about 15 days showed improvements in both constipation scores and gallbladder emptying compared to those who drank plain tap water. The evidence is limited, but what exists points in a positive direction.
What the Research Shows
The most-cited study on this topic split 21 patients with digestive complaints and constipation into two groups. One drank carbonated water, the other tap water, for roughly two weeks. Neither group knew which they were getting. By the end of the trial, the carbonated water group had better constipation scores and significantly improved gallbladder function. Gallbladder contraction increased from about 40% to nearly 54%, which matters because stronger gallbladder emptying pushes more bile into the intestines, and bile acts as a natural stimulant for the colon.
That said, this was a small study. Twenty-one people is enough to suggest a real effect, not enough to call it definitive. Larger trials haven’t been conducted specifically on carbonation and constipation, so the evidence is promising but thin.
How Carbonation Affects Your Gut
When you drink sparkling water, carbon dioxide is released in your stomach and intestines. This gas physically stretches the stomach wall, which triggers increased movement in the digestive tract. Multiple studies using bowel sound monitoring have confirmed that carbonated drinks boost gastric motility, the rhythmic contractions that push food through your system. More movement in the stomach generally translates to more movement downstream in the colon.
Carbonated water also shifts how food sits in your stomach after a meal. Research shows it pushes a greater proportion of both solid and liquid food into the upper part of the stomach, likely because the released gas creates gentle distension. This redistribution appears to stimulate the stomach’s natural emptying reflexes. While one study found that overall gastric emptying speed didn’t change with carbonation, the internal reshuffling of stomach contents may still help trigger the chain of digestive signals that eventually move things along in the intestines.
Mineral Water vs. Plain Sparkling Water
Not all carbonated waters are equal when it comes to constipation relief. Some of the benefit may come not from the bubbles themselves but from minerals dissolved in the water, particularly magnesium and sulfate. These two minerals have been used as laxatives for centuries, and their mechanism is straightforward: your gut can only absorb about 30% to 50% of the magnesium you ingest, and sulfate absorption is even more limited. The unabsorbed minerals draw water into the intestines through osmosis, softening stool and making it easier to pass.
Magnesium also appears to work through additional pathways beyond simple water retention. It stimulates the release of certain gut hormones and may increase production of nitric oxide, a molecule that relaxes smooth muscle in the intestinal wall. The practical takeaway: a carbonated mineral water that’s high in magnesium and sulfate will likely do more for constipation than a basic seltzer, which is just water and carbon dioxide with minimal mineral content. Check the label. Mineral waters vary enormously in composition, and the ones with higher magnesium and sulfate concentrations tend to produce more noticeable laxative effects.
Sparkling Water vs. Soda
The research supporting carbonation for constipation used plain carbonated water, not cola or other soft drinks. That distinction matters. Sugary sodas bring a host of other ingredients into the equation, including high-fructose corn syrup, phosphoric acid, and caffeine, all of which affect the gut in their own ways. Caffeine can stimulate colon contractions, but sugar-sweetened beverages are associated with poorer overall gut health and may worsen bloating for some people. Diet sodas introduce artificial sweeteners like sorbitol or sucralose, which can have laxative effects of their own but also cause gas and cramping.
If your goal is to ease constipation, plain sparkling water or sparkling mineral water is the cleaner option. You get the potential motility benefits of carbonation without the downsides of added sugars or artificial ingredients.
Possible Downsides
The same gas that stimulates gut movement can also cause bloating and discomfort, especially if you drink a lot at once. Carbon dioxide released in the stomach creates physical distension, and for people who are already feeling full or backed up, that added pressure may feel worse before it feels better. Carbonated water pushes more of your stomach contents upward, which can aggravate acid reflux in people who are prone to it.
For most people, moderate amounts of sparkling water are well tolerated. But if you have irritable bowel syndrome with a bloating-dominant pattern, or if you’re dealing with significant gas and distension alongside your constipation, carbonation could temporarily amplify those symptoms even if it helps move things along.
How to Try It
The constipation trial that showed positive results had participants drinking carbonated water consistently over about two weeks. This wasn’t a one-glass fix. If you want to test whether carbonation helps your constipation, commit to replacing some of your regular water intake with sparkling water for at least a week or two. Drinking it with meals may be particularly useful, since that’s when the motility-boosting effects of stomach distension are most relevant.
Choosing a sparkling mineral water with meaningful magnesium content gives you the best shot at results. Look for brands listing at least 50 to 100 milligrams of magnesium per liter. Pair this with the basics that matter more than any single beverage: adequate total fluid intake, fiber from whole foods, and regular physical activity. Carbonation is a reasonable addition to those fundamentals, not a replacement for them.