With a pH of 3.2, diet soda is very acidic. (As a point of reference, the pH of battery acid is 1. Water is 7.) The acid is what readily dissolves enamel, and just because a soda is diet doesn't make it acid-light. Adults who drink three or more sodas a day have worse dental health, says a University of Michigan analysis of dental checkup data. Soda drinkers had far greater decay, more missing teeth, and more fillings.
Photo by Getty Images Oct 25, 2012