In several observational studies, intake of carbonated beverages was associated with reduced bone mass or increased fracture risk, both later in life (1) and in children and adolescents (2–4). In most reports, colas were more strongly associated than were other carbonated beverages. Several investigators suggested that the factor or factors responsible for this association may be the increase in phosphorus intake or the net acid load of those beverages that use phosphoric acid as the acidulant or the caffeine of those beverages that are caffeinated. More recently, fructose, found in beverages that use natural sweeteners, was implicated as a possible cause of reduced calcium balance (5). For most of these factors, the effect is usually attributed to increased urinary calcium loss. Individually, phosphorus and caffeine were shown to have little or no net effect (6–11), but concern remains about the acid load (12). The combination of all 3 factors, as would be found in many colas, has not been directly tested.

The issue is especially important today because calcium intakes in North America fall far short of current recommendations. Per capita carbonated beverage consumption has risen dramatically, and carbonated sodas are now the preferred beverage of 20–40 y-old women (13). Interference in the calcium economy of persons with already low calcium intakes would only aggravate any calcium shortfall. This issue was studied in an experimental design only once before, and then only for a single cola (9). Accordingly, and because of the wide interest among nutritionists and dietitians in the possible effects of carbonated beverages, we undertook the present study. We investigated the acute effect on urinary calcium loss of intake of carbonated beverages of various compositions by adult women who were habitual users of such beverages.