Comparing the effect of calcium citrate supplement with normal calcium diet on metabolic risk factors in recurrent calcium stone formers with idiopathic hyperoxaluria: A randomized clinical trial

Abstract Background Calcium supplementation is only recommended to treat enteric hyperoxaluria, and its effect on idiopathic hyperoxaluria has not been thoroughly assessed. In this study, we compare the effect of calcium citrate supplementation with adequate dietary calcium intake on 24-hour urine (24-U) oxalate, calcium, and calcium oxalate supersaturation index (Ca Ox SS). Subjects: In a parallel-group controlled randomized clinical trial, 72 recurrent calcium stone formers with idiopathic hyperoxaluria were recruited from a tertiary stone prevention clinic in 2019–2020. 24-hour urine analyses and filling the 24-hour food recall were done at baseline and after eight weeks of intervention. Finally, 44 patients completed the study protocol. The participants were randomly assigned to receive adequate calcium through diet or taking 800 mg calcium citrate (in two divided doses with lunch and dinner) with a limited intake of dairy products. The study’s outcome was the change of 24-U Ox, Ca, and CaOx SS index after intervention. Results Findings showed that both interventions significantly reduced 24-U Ox (B Time effect: -10.06, 95% CI: -13.70, -6.42; p Time effect: -2.54, 95% CI: -4.06, -1.02; p = 0.001). After adjusting the effect of potential confounders through a Random-effects ML regression, the reduction of 24-U Ox remained significant. There was no significant increase in 24-U Ca in both intervention groups (p = 0.269). Conclusions Calcium citrate supplementation effectively reduces 24-U Ox levels comparably to adequate dietary calcium intake, without significantly raising 24-U Ca levels, offering a viable management option for calcium stone formers with idiopathic hyperoxaluria.