Effect of Phosphate-Specific Diet Therapy on Phosphate Levels in Adults Undergoing Maintenance Hemodialysis: A Systematic Review and Meta-Analysis

Abstract

Background and objectives: Hyperphosphatemia is a persistent problem in individuals undergoing maintenance hemodialysis, which may contribute to vascular and bone complications. In some dialysis centers, dietitians work with patients to help them manage serum phosphate. Given the regularity of hyperphosphatemia in this population and constraints on kidney dietitian time, the authors aimed to evaluate the evidence for this practice.

Design, setting, participants, & measurements: There was a systematic review and meta-analysis of clinical trials. MEDLINE, Embase, CINAHL, Web of Science, Cochrane Central Register of Controlled Trials, and other databases were searched for controlled trials published from January 2000 until November 2019 in the English language. Included studies were required to examine the effect of phosphate-specific diet therapy provided by a dietitian on serum phosphate in individuals on hemodialysis. Risk of bias and certainty of evidence were assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) method.

Results: Of the 8054 titles/abstracts identified, 168 articles were reviewed, and 12 clinical trials (11 randomized, one nonrandomized) were included. Diet therapy reduced serum phosphate compared with controls in all studies, reaching statistical significance in eight studies, although overall certainty of evidence was low, primarily due to randomization issues and deviations from protocol. Monthly diet therapy (20-30 minutes) significantly lowered serum phosphate in patients with persistent hyperphosphatemia for 4-6 months, without compromising nutrition status (mean difference, -0.87 mg/dl; 95% confidence interval, -1.40 to -0.33 mg/dl), but appeared unlikely to maintain these effects if discontinued. Unfortunately, trials were too varied in design, setting, and approach to appropriately pool in meta-analysis, and were too limited in number to evaluate the timing, dose, and strategy of phosphate-specific diet therapy.

Conclusions: There is low-quality evidence that monthly diet therapy by a dietitian appears to be a safe and efficacious treatment for persistent hyperphosphatemia in patients on HD.

Keywords: ESRD; chronic kidney disease; hemodialysis; hyperphosphatemia; nutrition; phosphorus.

Graphical abstract

Figure 1.

PRISMA flow diagram for systematic review examining the effect of providing phosphate-specific diet therapy by a dietitian in individuals with CKD. HD, hemodialysis; RDN, registered dietician. Reprinted from ref. , which is available under the terms of the Creative Commons Attribution License.

Figure 2.

Serum phosphate enrollment criteria at baseline affects changes in serum phosphate levels in reference groups of included studies in a systematic review. Black circles represent studies with no baseline requirement for participants’ serum phosphate levels; black squares represent studies in which participants were required to have recent hyperphosphatemia; white circles represent studies in which participants were required to have persistent hyperphosphatemia at baseline; white squares represent studies in which participants were required to have persistent hyperphosphatemia and hyperphosphatemia on most recent monthly blood test.

Figure 3.

Forest plot of included studies demonstrates that the intervention of providing phosphate-specific diet therapy by a dietitian reduces serum phosphate levels in individuals with CKD on hemodialysis. Conversion factors for units: serum phosphate levels in mg/dl to mmol/L ×3.096. 95% CI, 95% confidence interval.

Figure 4.

Randomized controlled trials (RCTs) and non-RCTs included in a systematic review examining the effect of phosphate-specific diet therapy provided by a dietitian on serum phosphate levels demonstrate high or some/moderate concerns in risk of bias. Risk of bias demonstrated in individual (A) randomized controlled trials (RCTs) and (B) non-RCTs included in a systematic review examining the effect of phosphate-specific diet therapy provided by a dietitian on serum phosphate levels.