According to Medscape, a study found that women who drink dark colas daily have lower bone density than women who drink colas or clear sodas less than daily. The cause of the lower bone density is not caffiene or sugar, as one might think, but is thought to be the phosphoric acid content in colas.

While it is true that phosphoric acid is also an ingredient in many dairy foods, it is balanced in those foods by the calcium content. It's believed that in colas, which contain no calcium, the phosphoric acid is not balanced and therefore binds with calcium in the body, keeping it from being absorbed.

Oddly enough, while this study found this to be true in women, it did not find the same to be true for men.

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