Effect of dietary treatment and fluid intake on the prevention of recurrent calcium stones and changes in urine composition: A meta-analysis and systematic review.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 33872340 · doi:10.1371/journal.pone.0250257
What was done
Authors conducted a systematic review and meta-analysis of randomized controlled trials searching PubMed, Web of Science, Embase, EBSCO, and Cochrane Library through November 2020 following PRISMA guidelines. They evaluated the effects of dietary treatments (low-protein with or without high-fiber; normal-calcium, low-protein, low-salt diet) and fluid intake on recurrent calcium stone formation and 24-hour urine composition across 6 included RCTs.
What was found
Low-protein diet with or without high fiber did not decrease stone recurrence compared with controls (RR = 2.32, 95% CI = 0.42-12.85; P = 0.34) with significant heterogeneity (I2 = 81%, P = 0.02), and showed no obvious changes in 24-hour urine sodium, calcium, citrate, urea, or sulfate across 4 reporting studies. A normal-calcium, low-protein, low-salt diet reduced recurrence compared to a normal-calcium diet alone, but specific numerical risk estimates were not reported in the abstract. Increased fluid intake significantly reduced stone recurrence (RR = 0.39, 95% CI = 0.19-0.80; P = 0.01) with low heterogeneity (I2 = 9%, P = 0.30).
Why it matters
This meta-analysis supports increased fluid intake as an effective strategy for preventing recurrent calcium nephrolithiasis, while indicating that isolated low-protein restriction is insufficient on its own.
Limits
Only 6 RCTs met inclusion criteria, and total participant counts are not stated in the abstract. Dietary protein comparisons exhibited high heterogeneity and wide confidence intervals. Specific numerical effect sizes for the multi-component dietary intervention were omitted in the abstract.
Cited by
- supports Maintaining a daily fluid intake of at least 2.5 liters dilutes urine sufficiently to prevent kidney stone formation.