Asked by: Mel Mitchell, by email
Hydration is just a fancy word for absorbing water. Since your digestive tract is a continuous unbroken tube that runs from your mouth to your anus, anything you swallow must either be absorbed or come out at the other end. If you don’t fully absorb the water in a drink, the inevitable consequence is diarrhoea. Carbonated water might make you burp, but it doesn’t give you diarrhoea, so it must hydrate you just as well.
Sugary drinks have a lower net hydration benefit because after the water has been absorbed, some of it must be used to digest the carbohydrate. Drinks containing alcohol or caffeine will be absorbed perfectly well, but they suppress the effect of antidiuretic hormone (ADH) and so cause you to produce more urine.
The most important factor in hydrating your body, though, is how much you drink. Most people get satiated on water much more quickly than with drinks that have something to make them more interesting – like flavour or sugar or fizz. So if you prefer carbonated water, you’re likely to drink more of it and it will therefore hydrate you better.