Good news: Sparkling water (including the flavored kind), which often helps with the taste fatigue some people experience with plain water, is just as hydrating as non-carbonated water.
If that's all you needed to know, you can stop reading. But if you want to know why, enjoy this cool, refreshing glass of explanation.
Sparkling water contains carbon dioxide, either naturally or added, which provides the carbonation, explained Melissa Majumdar, a registered dietitian, personal trainer and spokeswoman for the Academy of Nutrition and Dietetics.
But whether a beverage is carbonated has little effect on how well it keeps you hydrated, according to Ronald Maughan, a professor at the School of Medicine at St. Andrews University in Scotland and author of a recent study comparing the hydrating effects of beverages including still water, sparkling water, milk, colas, juice and coffee.
"The presence of carbonation has little effect on the body's response to ingested water," Maughan said. "We know that most of the gas comes out of solution in the stomach." An increased volume may slightly speed how quickly the beverage is emptied from the stomach and then absorbed in the small intestine and ultimately excreted from the body, he explained, "but the effect is small."
"Since water and carbonated water have the same base ingredient, they are in theory equally hydrating," Majumdar said. However, carbonation may affect how much water is actually consumed. "Some people find having the bubbles or a flavor help them drink more, while others feel full and bloated and may drink less with carbonated waters."
Other factors of carbonated drinks, aside from carbonation, can affect hydration. For example, waters with sugar, other nutrients or electrolytes are more hydrating than plain water or plain carbonated water.
"Adding large amounts carbohydrates or fat [such as natural sugars in orange juice or the fat in milk] will slow gastric emptying," Maughan said. Additionally, sodium (aka salt) in beverages acts like a sponge to hold water in the body. Potassium has been less well-studied than sodium, but there is some evidence that it can also help promote water retention in the body, according to Maughan.
So athletes who sweat a lot might be better off drinking lightly sweetened beverages or drinks with electrolytes -- but not necessarily carbonated beverages.
"During exercise, flat or still water is best," Majumdar said. That's because carbonation may cause bloating during physical activity and can prevent an athlete from drinking enough. Non-carbonated water is also best for anyone recovering from gastrointestinal surgery or for patients who feel full sooner than normal, Majumadar explained.