From
MSNQ: Is soda really bad for your kidneys?
A: Yes. Drinking 16 ounces or more daily (whether diet or regular) doubles your risk of chronic kidney disease, according to an NIH study of more than 900 people. The researchers already knew that consuming any type of soft drink—the average American adult guzzles 59 gallons' worth per year—is associated with several risk factors for kidney disease (hypertension, diabetes, and kidney stones), but the spike in the cola category was remarkable.
Experts suspect that the ingredient phosphoric acid may be the culprit; it's been repeatedly linked to "urinary changes that promote kidney stones," say the study authors. Cola has an additional knock against it: Consumption is associated with significantly lower bone density in women, increasing the risk of osteoporosis and bone fractures, says a separate study.
Learn why diet soda isn’t healthy for you