Carbonated water, also known as seltzer water or club soda, is another story. Seltzer is made by infusing the gas carbon dioxide (CO2) into plain water. Once in the water, a mild acid, carbonic acid, is formed. Much of this acid is released when the cap is removed and the pressure is let off. While some of the carbon dioxide escapes with the bubbles, the remaining CO2 is ingested with the water. More CO2 will also exit the body in the characteristic belch associated with drinking any carbonated beverage.

While carbonated water itself does not pose the same risks as soda, it can contain some ingredients that may surprise you. Some flavored seltzer contains sweeteners, and many have added mineral salts to balance the pH. The primary mineral salt is sodium bicarbonate, making it higher in sodium than you might think.

For the most part, an occasional drink of carbonated water is not a problem, especially if it is a brand with no added ingredients. On the other hand, it's possible that long-term consumption of large quantities (even without the added ingredients) may pose a health problem down the road. Although it may be boring advice, moderation is generally the key to safeguarding your health, even with more benign habits. Alternate your consumption of carbonated water with what the Europeans call "flat" bottled water and you should be fine