To evaluate the effect of cola consumption on urinary stone risk factors in a controlled metabolic environment with a prospective cross-over study.

Thirteen participants (10 normal and 3 calcium oxalate stone-formers) underwent 2 6-day phases on a controlled metabolic diet. During phase 1, subjects ingested 1 liter of cola daily, followed by a 3-week washout period. During phase 2, subjects ingested 1 liter of deionized water daily. Twenty-four–hour urine collections and serum metabolic panels were obtained for stone risk factors at the end of each phase. Urine and serum results of the cola phase were compared with those of the water phase.

Normal subjects and stone-formers were combined for analysis after determining no significant difference between the 2 groups. No significant differences were found among cola and water treatment groups for normal subjects, stone-formers, or the pooled group.

Cola exerts no detectable change in urinary risk factors associated with calcium oxalate stone formation. Cola consumption may not increase stone risk and may be an acceptable alternative source of daily fluid for patients unwilling to increase water consumption.