The effects of drinking bicarbonate-rich mineral water in calcium oxalate stone formers: an open label prospective randomized controlled study in an Asian cohort

Purpose To examine the effects of drinking bicarbonate-rich mineral water in patients with calcium oxalate stones. Materials and methods This was an open label prospective randomized controlled study comparing the effects of a bicarbonate-rich mineral water versus plain water on urine biochemistry in patients with calcium oxalate stones. The mineral water group were instructed to consume 1.25 L of mineral water per day at meal times, and supplemented by plain water. Their total intake was up to 3 L/day. Control group consumed only plain water up to 3 L/day. 24 h urine analyses were performed at baseline, 1, 4, 8 and 12 weeks after starting protocol. Results 58 patients were recruited for the study. 51 patients were included in the final analysis. Baseline data were comparable between the two groups. Over the course of 12 weeks, compared to patients drinking plain water, those drinking mineral water had higher overall urinary volume (difference = 644.0 ml/24 h, 95% CI = (206.7, 1081.3)), higher overall urinary magnesium (difference = 1.894 mmol/24 h, 95% CI = (1.006, 2.782)), and pH (difference = 0.477, 95% CI = (0.149, 0.804)). However, there was no difference in urinary oxalate and Tiselius index. Mineral water group had net increase of urinary citrate (at each study point compared to baseline) which was sustained until week 12, whereas plain water group showed no significant change. Conclusions Drinking bicarbonate-rich mineral water in calcium oxalate stone formers increased stone inhibitors such as magnesium, citrate and moderate degree of urinary alkalinization compared to patients drinking plain water, but it did not alter Tiselius index or urinary oxalate after 12 weeks.