Kidney stones are hard collections of minerals that develop in the small nephrons of your kidneys. Although kidney stones are typically small, your nephrons are, too, and the development of kidney stones can lead to painful symptoms. If you experience kidney stones once, you are likely to have them again, which means your physician may recommend changing your diet slightly to reduce the likelihood that kidney stones will form. One change could be to limit the amount of dark colas, such as classic Coke, in your daily intake.
Significance
Coke has been linked with the formation of kidney stones because it contains phosphoric acid. This acid is problematic if you are prone to kidney stone formation, because it reduces the amount of citrate in your urine. Citrate is important because it prevents calcium from binding with other minerals to form kidney stones. Phosphoric acid also can increase the acidity of your urine, which provides a better environment for kidney stones to form.
Dark vs. Light Sodas
Classic Coke is an example of a dark soda, which contains phosphoric acid to give the drink its flavors. However, not all sodas contain this acid. Light-colored sodas, such as those that are lemon-lime or citrus-flavored, contain citric acid, which also is known as citrate and has protective effects against kidney stones. This is why physicians may not caution against consuming all sodas because some types can have protective benefits.
Coca-Cola Response
The Coca-Cola Company, which is responsible for manufacturing classic Coke, released a statement addressing its product and the incidence of kidney stones on the company's website. On the site, the company says there are numerous causes of kidney stones and that "cola beverages have not been shown to cause them." The company also says that classic Coca-Cola has significantly less phosphorus than many other common foods in your daily diet. Coke has about 17 mg per 100 g serving while the same serving size of milk has 93 mg and the same serving size for cheddar cheese has 512 mg of phosphorus. The company also says the National Kidney Foundation does not have Coca-Cola on its list of food products to limit to reduce kidney stone formation.
Considerations
While Coke does not have as significant phosphorus acid levels as other products, the amount of phosphorus can be increased if you consume a significant amount of Coke per day. Because the 100-g serving mentioned in Coca-Cola's measurements is the equivalent to about 3.5 oz. of Coke, drinking a 12 oz. can increases the amount of phosphorus by almost four times. This means moderation can be important in drinking Coke if you are prone to kidney stone formation.
