http://www.eurekalert.org/pub_releases/2006-10/tu-ccm100306.php

Tucker, also a professor at the Friedman School of Nutrition Science and Policy at Tufts, and colleagues analyzed dietary questionnaires and bone mineral density measurements at the spine and three different hip sites of more than 2,500 people in the Framingham Osteoporosis Study whose average age was just below 60. In women, cola consumption was associated with lower bone mineral density at all three hip sites, regardless of factors such as age, menopausal status, total calcium and vitamin D intake, or use of cigarettes or alcohol.

However, cola consumption was not associated with lower bone mineral density for men at the hip sites, or the spine for either men or women. The results were similar for diet cola and, although weaker, for decaffeinated cola as well.

Men reported drinking an average of six carbonated drinks a week, with five being cola, and women reported consuming an average of five carbonated drinks a week, four of which were cola. Serving size was defined as one bottle, can or glass of cola. "The more cola that women drank, the lower their bone mineral density was," says Tucker, who is corresponding author of the study. "However, we did not see an association with bone mineral density loss for women who drank carbonated beverages that were not cola."