Is sparkling water as hydrating as still water?

Carbonated sparkling water hydrates as effectively as still water, the carbon dioxide in carbonated water does not impair fluid absorption, does not reduce bioavailability of hydration, and does not acidify body fluids meaningfully (the CO2 is expelled as gas or metabolized by carbonic anhydrase), though for active exercise, the gastric bloating from carbonation makes still water more practical during physical effort (Tsereteli et al., Eur J Clin Nutr, 2004).

The acid erosion concern with sparkling water applies only to flavored sparkling water with added acids (citric acid in many flavored brands) at very high and frequent consumption, plain sparkling water (San Pellegrino, Perrier, unflavored seltzer) is essentially pH-neutral to slightly acidic (pH ~5.5) and does not cause meaningful dental enamel erosion at normal consumption frequencies. For men who dislike plain water and consume sparkling water instead, the hydration equivalency makes sparkling water a perfectly valid hydration strategy.

Honesty Scale: Solid (1) for equivalent hydration from sparkling water. Solid (1) for the acid erosion concern being limited to flavored sparkling water at high frequencies.

What to do: Unflavored sparkling water is as effective as still water for hydration. If you prefer carbonated water, use it freely. Avoid sweetened sparkling waters, flavored seltzers with citric acid as a primary ingredient, and sodas, these are dehydrating sugar vehicles, not hydration tools.

For the full picture, read The Hydration Deep Dive