Carbonated water does not cause constipation. In fact, the available clinical evidence points in the opposite direction: sparkling water may actually help relieve it. The confusion likely comes from the bloating and gas that carbonation can cause, which people sometimes associate with digestive problems. But when it comes to bowel regularity specifically, the bubbles appear to be more helpful than harmful.
What Clinical Trials Actually Show
A randomized trial of patients with both functional dyspepsia and constipation found that drinking carbonated water significantly improved constipation symptoms, while tap water did not. The same study found that carbonated water improved gallbladder emptying, with contraction rates jumping from about 40% to nearly 54%. Better gallbladder function supports digestion overall, which can help keep things moving through your gut.
A separate double-blind study focused specifically on elderly stroke patients who were bedridden and chronically constipated. After two weeks of drinking carbonated water instead of tap water, the group drinking sparkling water had significantly more frequent bowel movements and fewer constipation symptoms. This is notable because bedridden patients are among the most constipation-prone populations, and even in that group, carbonated water made a measurable difference.
How Carbonation Affects Your Gut
The carbon dioxide dissolved in sparkling water creates mild pressure in your stomach, which appears to stimulate digestive activity. One study found that carbonated water didn’t change overall gastric emptying speed, but it did change where food sat inside the stomach, pushing a greater proportion of both solids and liquids into the upper stomach. This redistribution seems to trigger reflexes that promote movement further down the digestive tract.
Carbonated water also hydrates you just as effectively as still water. Since dehydration is one of the most common causes of constipation, this matters. Some people worry that the fizz somehow reduces how well their body absorbs the water, but research on beverage hydration confirms sparkling water performs the same as flat water. Your colon pulls water from stool when your body is dehydrated, making it harder and more difficult to pass. As long as you’re drinking enough, sparkling water keeps stool soft just as well as any other water.
The IBS and Bloating Factor
There is one important caveat. While carbonated water helps with constipation in most people, it can worsen symptoms if you have irritable bowel syndrome. A cross-sectional study of carbonated soft drink consumers found they were more than three times as likely to have IBS compared to non-consumers. Among women specifically, drinking carbonated beverages increased the predicted probability of IBS by about 25 percentage points. Other research has confirmed that people with IBS report more gastrointestinal complaints from carbonated beverages than people without the condition.
The mechanism is straightforward: the dissolved gas expands in your intestines, causing bloating, distension, and discomfort. For someone whose gut is already hypersensitive, that added pressure can trigger cramping and irregular bowel patterns, including constipation. If you have IBS and notice that sparkling water makes your symptoms worse, switching to still water is a reasonable move. For everyone else, the carbonation itself isn’t a problem.
Flavored Sparkling Water Is a Different Story
Plain carbonated water and flavored or sweetened sparkling water are not the same thing when it comes to your digestion. Many flavored varieties contain artificial sweeteners, which can cause their own stomach issues. Some sugar alcohols commonly used in “zero calorie” drinks are known to pull water into the intestines and cause bloating, gas, or diarrhea at moderate doses, while sugar itself contributes to a range of chronic health problems. As Cleveland Clinic dietitians recommend, the best sparkling water is the simplest kind: just water and carbonation, nothing else added.
If you’re drinking a flavored sparkling water and noticing digestive changes, check the ingredients list before blaming the bubbles. The sweetener or additive may be the actual culprit.
Practical Tips for Using Sparkling Water
If you’re mildly constipated and looking for a simple, low-risk intervention, swapping some of your daily still water for plain carbonated water is worth trying. The clinical trials that showed benefits used regular daily intake over one to two weeks, so a single glass probably won’t produce dramatic results. Consistency matters more than volume.
Drinking it with meals may offer the most benefit, since that’s when the stimulation of gallbladder emptying and gastric redistribution is most relevant. Cold sparkling water also tends to hold its carbonation better, delivering more of the dissolved gas that drives the digestive effects. There’s no established “dose” from the research, but the studies generally used normal drinking amounts, not excessive quantities, so your regular water intake swapped to sparkling is a reasonable starting point.