They may contain zero calories, no sugar and provide an energy boost, but diet soda could drain calcium and phosphorous from your body, according to a preliminary study presented at a medical convention.
A small study from the Walter Reed Army Medical Center reported that healthy women who drank diet cola excrete more calcium and phosphorous than non-cola drinkers. In the study, 20 health women were randomized to drink 24 ounces of water or diet cola on two days. Their urine was collected up to three hours later.
Those who drank diet cola excreted more calcium and phosphorous than the control group. The mean calcium excretion three hours after drinking cola was 6.85 milligrams higher than after drinking water. Mean phosphorous excretion was 41 milligrams higher in the cola group than the control group, according to the abstract. Calcium and phosphorus are both important nutrients that work together to build strong bones and teeth.
Previous studies have reported that cola drinkers (both diet AND regular soda) have lower bone mineral density and increased fracture rate compared to non-cola drinkers
With all the studies done, it is hard to say if this is in fact true. Another thing is it is a small study, so it may not provide enough evidence to prove the theory.