1. Soda makes you fat. Both regular and diet soft drinks are tied to obesity. In one study, people who drank diet sodas had a 70% greater increase in waist circumference over a few years compared to those who skipped soft drinks.
Diet soft drinks are particularly insidious, says RealAge cofounder Michael F. Roizen, M.D. "Sweet diet soda fuels your desire for other sweets," he explains. It also has a "health halo" effect. "You view choosing a 'diet' drink as virtuous (all those calories saved!). So it feels like you can afford to reward that virtue with a hot fudge sundae."
2. Soda boosts your risk of serious disease. The extra belly fat that often comes with a soft drink habit is linked to heart disease and type 2 diabetes. A recent study in the Journal of Internal Medicine also tied a daily diet soda habit to a higher stroke risk.
3. Regular soft drinks may cause cancer. New research from the University of Minnesota School of Public Health finds drinking two or more regular soft drinks per week may almost double your risk of pancreatic cancer. Researchers speculate that the sugar overload from regular soda triggers insulin production that fuels cancer cell growth.
4. It's bad for your teeth. Yep, your mom was right about this one. And here again, even diet soda is bad news because sugar isn't the worst offender in soft drinks. The big culprit is soda's high acid content: phosphoric, malic, citric, and tartaric acid strip tooth enamel. Citrus-flavored soft drinks are the worst -- they dissolve enamel up to five times more than colas.
5. It's bad for your bones. The same acids that are bad for your teeth also coax calcium from your bones. That goes for regular and diet caffeinated soda. Can't give up your Diet Coke? Roizen recommends upping your daily calcium tally by an extra 20 mg for every 12 ounces of soda you sip.
6. It's bad, even if you don't gain weight. New research from the American Heart Association finds that women are more vulnerable than men to the harmful effects of drinking two or more sugar-sweetened drinks -- including soda -- per day. Soda-sipping women are likely to have a larger waist size, higher "bad" LDL cholesterol, higher levels of triglycerides (harmful fatty acids that can cause heart disease), higher blood sugar, and lower "good" HDL cholesterol -- even if they don't put on a pound.