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Take a spin through the nearest grocery store, or rummage through the cooler at any party, and you’re bound to encounter a can of carbonated water. The market, which used to be dominated by LaCroix, Perrier, and San Pellegrino, is home to a robust class of newcomers like ,��, and . And , formerly an under-the-radar classic,��has developed a devoted fan base,��with familiar flavors like lime and grapefruit, though it’s increasingly sharing shelf space with options like blackberry-cucumber and pear-kiwi.

Most seltzer waters are sugar- and calorie-free, which many people use as a license to chug the stuff like it’s plain old water. As a professional runner, I’m guilty, too. My races this summer have been a cruel mix of hot and humid, and I have yet to find anything as refreshing as a little post-race fizz. But when I found myself four seltzers deep one Sunday at 10 A.M., I couldn’t help but wonder: Was I really hydrating myself? How was the carbonation impacting my recovery? And is there any reason I should limit my seltzer consumption near workouts or in general? I called up Laura McClure, a former Division I runner and a registered dietitian with a master’s degree in exercise and sports nutrition, to help set the record straight.

What Is Sparkling Water Anyway?

Seltzer water, sparkling water, and sparkling mineral water all fall under the carbonated-water umbrella. What differentiates them is their carbonation methods, water sources, and added ingredients (or lack thereof). San Pellegrino and Topo Chico, whose waters come from natural springs containing minerals such as magnesium, calcium, and zinc, are considered sparkling mineral water. Depending on their water source, these can be either naturally or artificially carbonated.

Members of the seltzer family, on the other hand, are derived from regular (rather than mineral) water and then artificially carbonated. Also called sparkling, bubbly, and fizzy water, this category includes LaCroix, Waterloo, and other similar beverages. Artificiality, McClure clarifies, is not inherently bad; in this context, it just means that carbon dioxide has been added to the water under pressure to give it effervescence (as opposed to naturally occurring carbonation found in some mineral springs).

Can I Use It for Hydration? 

Here’s the good news: carbonated water hydrates just as well as regular water, says McClure. But before you start filling your water bottles and CamelBaks with Spindrift, keep in mind that sparkling water doesn’t feel the same as flat water—especially while you’re also pushing your body. Effervescence tends to cause gastrointestinal discomfort in the form of bloating, cramps, and a false sense of fullness, none of which are desirable during a workout or race, and all of which can be exacerbated in people with heightened sensitivity and existing digestive-tract conditions. Keep in mind, too, that long and strenuous activities often necessitate fluids with electrolytes and carbohydrates. In those situations, you’re better off sipping more traditional (read: flat) sports drinks.

Is It Bad for Me in Any Way?

Contrary to , McClure says that sparkling water has not been shown to affect bone density. It can, however, erode tooth enamel over time while also causing heartburn because it is more acidic than flat water. The pH depends on the amount of carbonation (the more bubbles, the lower the pH) and varies by brand, but on a pH scale of zero (highly acidic) to fourteen (highly alkaline),��most seltzers fall between three and four. Pure water, for context, has a neutral pH of seven, and tooth erosion can occur at levels of four and below. The speed of that erosion depends on your personal drinking habits and the strength of your enamel. To be safe, you can combat a drink’s acidity by eating something at the same time, following sips with plain water, and minimizing tooth exposure by using a straw. In addition, watch out for cans with citric acid, which lowers the drink’s pH even further.

What About Added Ingredients? 

Even within the same category, not all bubblies are created equal. The nutrition label says it all, and as with food, the shorter the ingredient list, the better. “Carbonated water, with natural fruit essences if you’re opting for a flavored variety, should be it,” advises McClure. She suggests avoiding sweeteners, sodium, preservatives, and other additives. And as for Bon and Viv, Truly, White Claw, and the rest of the hard-seltzer lineup that’s quickly gaining steam? With roughly 4 to 8 percent alcohol by volume, they’re comparable to beer, says McClure. Even the purest sparkling-water ingredients won’t counteract the dehydrating powers of alcohol.

So Should I Keep Drinking It?

Carbonated water, from this running dietitian’s perspective, is a neutral hydrator for athletes: it’s absolutely better than drinking nothing, on par with flat water when consumed moderately and after working out, and negative when consumed in excess (because of possible tooth erosion), at the wrong time (like before a run), or with unnecessary additives (like sugar and alcohol). “Just like pre-race meals and midrace fluids,” McClure explains, “seltzer affects individuals differently.” So tune in to the way sparkling water makes you feel at different times, and find some flavors you like that have bare-bones ingredients. If you’re going to crush a case a week, after all, you might as well go for the good stuff.