Do carbonated drinks cause bloating? What the research says

Swapping soda for sparkling water cuts the sugar. Whether it cuts the bloating is a different question, and the research gives a more nuanced answer than either "bubbles are fine" or "bubbles are the enemy."

Here's what studies have measured when people drink carbonated drinks, and how to work out whether they matter for you.

What carbonation does in the stomach

Carbonated drinks bring gas with them, and imaging shows it. In an Italian MRI study, 10 healthy young adults drank 300 ml of a no-calorie carbonated drink, the same drink without bubbles, or water before a meal. Stomach volume right after drinking was significantly higher with the carbonated version. By the time participants felt full, though, stomach volume was similar across the three drinks, and they ate about the same amount (Cuomo et al., 2011).

A Dutch study looked at how that fullness feels. Thirty-four healthy adults, half of them women, drank 500 ml of beer or soda on separate days while MRI tracked their stomach contents. Across both drinks, the feeling of bloating was most closely linked to total stomach volume. Women retained more liquid in the stomach than men, and the researchers suggested that discomfort in women may be related more to fluid than to gas (Camps et al., 2018).

Taken together, these studies suggest that a carbonated drink temporarily adds volume, and that volume is what you tend to feel.

How much seems to matter

A review of the research by gastroenterologists in Naples concluded that symptoms from mechanical stress on the stomach appear only when drinking more than 300 ml of a carbonated fluid (Cuomo et al., 2009). That's roughly 10 ounces, a little less than a standard 12-ounce can.

The same review noted that more studies, especially intervention trials, were needed before making claims about benefits, and that possible drawbacks such as stomach discomfort also needed more research (Cuomo et al., 2009). In other words, this is not a closed case.

A surprise: sparkling water helped in one small trial

In a double-blind trial from the same Naples group, 21 people with functional dyspepsia and constipation drank either carbonated water or tap water for about 15 days. In the carbonated water group, the dyspepsia score dropped from 7.9 to 5.4 and the constipation score from 16.0 to 12.1, while the tap water group's scores didn't change significantly. The carbonated water group could also take in more of a liquid test meal before feeling full (Cuomo et al., 2002).

That's a small, short study, so it's a reason for curiosity rather than a recommendation. It does suggest that sparkling water isn't automatically a problem for everyone with a sensitive gut.

What about reflux?

Carbonated drinks often get blamed for heartburn. A systematic review found that they cause a very short drop in pH in the esophagus and may briefly lower the pressure of the valve between the esophagus and stomach. But they haven't been consistently shown to cause reflux symptoms, and the authors found no direct evidence that they promote or worsen reflux disease (Johnson et al., 2010).

What the research doesn't cover

Most of these studies were short and small, and several used healthy young adults. None followed women in their forties and fifties with afternoon bloating over months. The studies also can't separate the bubbles from everything else in a drink, from sugar and sweeteners to added fibers.

Should you skip the bubbles?

Not necessarily. A practical approach:

• Match the test to your symptom. If your main complaint is upper-belly fullness or belching, a two-week break from carbonated drinks is a reasonable experiment. If your bloating sits lower down and builds through the afternoon, look at food, fiber and bowel habits too.
• Watch the serving size. Pour a glass rather than finishing a large bottle, and sip it slowly.
• Read the label. Some "gut health" sodas add prebiotic fibers. Here's why inulin can backfire for a sensitive gut.
• Keep what works. If sparkling water helps you drink more water and your gut feels fine, the research above doesn't give you a reason to quit.

A two-week bubble test

1. Week 1: drink as usual, but write down every carbonated drink, how much and when.
2. Each afternoon, rate upper fullness and lower bloating separately from 0 to 10.
3. Week 2: switch to still drinks, keeping food and everything else as similar as you can.
4. Compare the two weeks. If nothing changes, bubbles probably aren't your main trigger. If upper fullness drops, try reintroducing a smaller glass and see where your comfortable limit is.

When to see a doctor

• Heartburn on most days, or reflux that keeps coming back
• Trouble swallowing or pain when swallowing
• Early fullness that's new and persistent, especially with weight loss, vomiting or pelvic pain
• Black stools or anemia

Sources

1. Cuomo R, Savarese MF, Sarnelli G, et al. The role of a pre-load beverage on gastric volume and food intake: comparison between non-caloric carbonated and non-carbonated beverage. Nutr J. 2011;10:114. PMID 21999723
2. Camps G, de Graaf K, Smeets PAM. Men and women differ in gastric fluid retention and neural activation after consumption of carbonated beverages. J Nutr. 2018;148(12):1976-1983. PMID 30517723
3. Cuomo R, Sarnelli G, Savarese MF, Buyckx M. Carbonated beverages and gastrointestinal system: between myth and reality. Nutr Metab Cardiovasc Dis. 2009;19(10):683-9. PMID 19502016
4. Cuomo R, Grasso R, Sarnelli G, et al. Effects of carbonated water on functional dyspepsia and constipation. Eur J Gastroenterol Hepatol. 2002;14(9):991-9. PMID 12352219
5. Johnson T, Gerson L, Hershcovici T, Stave C, Fass R. Systematic review: the effects of carbonated beverages on gastro-oesophageal reflux disease. Aliment Pharmacol Ther. 2010;31(6):607-14. PMID 20055784

This article is for general information and isn't medical advice. If you have frequent heartburn, upper abdominal fullness or other ongoing digestive symptoms, talk to your healthcare provider.