Carbonated Drinks and Calcium Absorption

Q:  I recently read an article that advised: "Avoid soft drinks; their phosphoric acid may promote calcium loss." Is this true? I do have osteoporosis and take calcium as well as Miacalcin. However, I also usually drink a glass of diet cola every day. According to the bottle, it contains aspartame (whatever that is) and it reads, "Phenylketonurics, contains Phenylalanine." Do you consider soft drinks containing the above chemicals to be harmful and to cause calcium loss?

A:  I also have heard several times that carbonated drinks are not good for your bone because of the phosphorus. Two different reasons have been given: 1) phosphorus binds to the calcium in your stomach and prevents absorption of the calcium into your blood, and 2) high phosphorus in your blood draws calcium out of your bones. When I searched recent medical articles and textbooks (for hours!), I could find nothing supporting this.

Caffeine does decrease bone mass and increase risk of hip fracture. In a study of 9,615 women over age 65, those who drank 190 mg a day of caffeine had a 20% to 30% increased risk of hip fracture. Sodas have about 40 mg of caffeine per can and brewed coffee about 100 mg per cup.

Aspartame (Nutrasweet) is a sugar substitute that contains phenylalanine. It has no harmful effect on bones.

"Dear Doctor" is a compilation of patient questions answered by doctors from the Medical College of Wisconsin.