Your dentist will tell you (if she hasn't already!) that sodas have two major strikes against them: the sugar, which contributes to tooth decay and cavities, and the acids, which destroy the enamel on your teeth.
According to the Center for Science in the Public Interest, the average 12-ounce (340.2-gram) can of soda contains about 10 teaspoons (40 grams) of sugar. To put that amount into perspective, the USDA recommends that added sugars account for no more than 6 to 10 percent of our total calories. That means just one can of soda contains the maximum daily sugar allotment for someone who consumes 2,000 calories a day.
Diet soda drinkers: You're not off the hook. Diet sodas may be free of sugar, but they contain just as much acid as regular sodas. Phosphoric acid and citric acid, the two acids most commonly found in sodas, are added for their sharp, tangy flavors. Unfortunately, these ingredients also make sodas extremely bad for your teeth.
Acids weaken the teeth by dissolving and softening hard enamel, making teeth more prone to cavities, decay and sensitivity. The Minnesota Dental Association has found that exposure to acidic foods or beverages with pH values less than 4 can result in dental erosion. They also found that most sodas fall well below that threshold. Cola drinks were the most acidic, with pH levels ranging from around 2.5 (Coca-Cola and Pepsi) to 2.9 (Dr. Pepper). Several orange and lemon-lime soda drinks came in around the 3 mark. Root beer, which is often less carbonated than other sodas and less likely to contain citric and phosphoric acids, fared slightly better, with a pH above 4.
Fizzy sodas also contain carbonic acids, which are weak acids produced when the carbon dioxide gas that gives soda its distinctive bubbles dissolves in water. Even unflavored carbonated drinks like seltzer and club soda contain carbonic acids, making them slightly acidic, but nearly all the acidity in soda comes from citric or phosphoric acid, not the carbonation itself.
To be fair, non-carbonated beverages such as orange juice and lemonade can be just as sugary and acidic as sodas. But it's not often that you see someone leave a convenience store sipping from a giant 32-ounce (907.2 gram) cup of OJ. Popular sport drinks and energy drinks are also a concern, as they tend to be packed with sugar -- 5 to 12 teaspoons (25 to 59 grams) per serving, highly acidic (Gatorade has a pH of around 2.9, depending on the variety), and, unlike good old OJ, heavily consumed by teens and young adults. Even flavored waters (both sweetened and sugar free) can be fairly acidic, since they often contain citric acid in addition to the naturally occurring carbonic acids.
If soda can do this much harm to your teeth, what is it doing to the rest of your body? We thought you'd never ask.