Over the past few decades the water industry has multiplied in size. Dozens of brands of bottled water line supermarket shelves. Labels highlight PH, carbonation, minerals, and electrolytes. There are ongoing debates about alkaline water, coconut water, and sparkling water; are they more or less hydrating than still water?
First, we need to define what “sparkling water” is. What you refer to as “sparkling water” actually makes a difference in terms of hydration. Carbonated water, sparkling water, bubbly water, and fizzy water are all general terms that reference H2O (water) that has been pressurized with CO2 (carbon dioxide). Ordering one of those at a restaurant might land you with any number of beverages that all have different attributes in terms of taste and hydration benefits.
Seltzer refers to a drink that includes water and carbonation, but nothing else. Carbonation itself doesn’t alter the hydrating potential of a drink. Multiple studies show that seltzer does not dehydrate you; the only real difference between tap water and seltzer that seltzer is carbonated. If you were inhaling the seltzer that would be a problem (for many reasons), but your digestive system can handle it. The only way seltzer will hydrate you less than regular water is if you drink less of it.
Club soda is a type of sparkling water that has added sodium and/or potassium salts. This is where it gets a little more confusing. When I first read that, I was confused, because sodium is salt, and surely that must mean club soda is less hydrating than water. However- sufficient levels of sodium (and potassium) are necessary for hydration to be able to happen. This is because water essentially “follows” sodium, which increases water retention. Salts help to lock water into your cells and insure that they stay hydrated. It is just as dangerous to have too little sodium as it is to have too much, and without enough sodium any hydration you achieve is short-lived.
As long as you’re getting enough sodium in your diet club soda won’t hydrate you any more than flat water. However, if you aren’t getting enough salt in your diet, club soda might hydrate you more than other alternatives.
Perrier and San Pellegrino are popular sparkling water brands. Both types have a number of other mineral components, and both are slightly acidic. Neither of the two are acidic enough to cause dehydration, or any potentially negative impacts. They’re well within the range that science deems safe, and closer to neutral than some non-carbonated brands of bottled water. However, the mineral content of these two drinks might be cause for pause. They both include a number of minerals that are essential for hydration (calcium, magnesium, chloride). However they also include sulfates which are known to have a laxative effect in the presence of calcium and magnesium. It is likely that the trace amounts of minerals in bottles water are not likely to be concentrated enough to cause any harm.
If you are sick, or really, dangerously dehydrated, drinking Perrier or San Pellegrino is probably slightly less hydrating than drinking still water or seltzer. In everyday situations, the difference is likely marginal at most.
Tonic water is sparkling water that has added sugar as well as an ingredient called quinine. Quinine can be dangerous if consumed in large amounts, but you would have to drink quite a bit of tonic water to see these effects. Sugar can facilitate faster absorption of water into the blood stream, in small amounts, but this is only super relevant to hydration in the middle of an intense workout.
Tonic water is closer to a soft drink than anything else. To consume it in the place of water would increase both sugar and quinine levels. While neither of these things would dehydrate you, they are not great health-wise.
Unless you are very sick or an athlete, the differences between all these drinks are so small that they will not make a significant difference in your hydration. The best thing you can do for your body is to stay hydrated. Even after introducing the question of carbonation, hydration is still a question of making sure that you drink enough.
By Kate Marin | @ikate186