Dietary Therapy in Dialysis Patients

Patients with end-stage kidney disease have hyperphosphatemia and accumulated uremic toxin level due to decreased urine excretion ability. Unhealthy diet causes altered mineral metabolism, elevated uremic toxin level, immune dysregulation, and inflammation. The investigators hypothesize that therapeutic diet intervention reverses altered mineral metabolism, elevated uremic toxin level, immune dysregulation, and inflammation. In this study, the investigators crafted 7-day special healthy diet to illustrate the clinical implications of therapeutic diet for dialysis patients.

The risk of cardiovascular disease (CVD) and mortality in patients with end-stage kidney disease (ESKD) is far greater than those in the general population. Emerging evidence suggests that unhealthy diet causes altered mineral metabolism, disturbance of gut microbiota (dysbiosis) with elevated uremic toxin level, immune dysregulation, and inflammation; these abnormalities are strongly related to development of CVD. Little is known about the relationship between therapeutic diet intervention and cardiovascular risk in patients with ESKD. Recently, the study of the investigators showed that ESKD patients undergoing hemodialysis who consumed very low-phosphate diet, phosphate-to-protein ratio (PPR) value of 8 mg/g, experienced an extra reduction of serum phosphorus level by 0.61 mg/dL compared with that of low-phosphate diet, PPR value of 10 mg/g. The aim of the study is to explore the effect of 7-day therapeutic diet intervention on changes of altered mineral metabolism, uremic toxin production, immune dysregulation and inflammation, highlighting the important role of dietary modification in dialysis population. It is to conduct a randomized controlled trial with cross-over design at a hemodialysis unit of tertiary teaching hospital in Northern Taiwan. Subjects with aged older than 20 years, ESKD undergoing maintenance dialysis for more than three months, having adequate dialysis and serum intact parathyroid hormone less than 800 pg/mL will be included. Participants will be randomly assigned into two groups: those in group A will receive study diet for 7 days, followed by 4-week washout period and then receive 7-day usual diet. The opposite order of diets will be prescribed in group B. The study meals are prepared in the hospital cafeteria. Dietary compositions of the study diets were analyzed before the start of the study. The study outcome measures are difference in change-from-baseline values of altered mineral metabolism, uremic toxin production, immune dysregulation and inflammation between the therapeutic diet and the usual diet.

7-day usual diet as control group, no dietary intervention in this group, participants consumed their habitual diet

Difference in change-from-baseline intact fibroblast growth factor 23 (pg/mL) between therapeutic diet and usual diet

Difference in change-from-baseline C-terminal fibroblast growth factor 23 (RU/mL) between therapeutic diet and usual diet

Difference in change-from-baseline intact parathyroid hormone (pg/mL) between therapeutic diet and usual diet

Difference in change-from-baseline free indoxyl sulfate (mg/L) between therapeutic diet and usual diet

Difference in change-from-baseline free p-cresol sulfate (mg/L) between therapeutic diet and usual diet

Difference in change-from-baseline C-reactive protein (mg/dL) between therapeutic diet and usual diet

Difference in change-from-baseline absolute number (per μl blood) of CD4+ T cells between therapeutic diet and usual diet

Difference in change-from-baseline absolute number (per μl blood) of CD8+ T cells between therapeutic diet and usual diet

Difference in change-from-baseline absolute number (per μl blood) of monocytes between therapeutic diet and usual diet

Difference in change-from-baseline percentage (%) of CD4+ (cluster of differentiation 4) T cells between therapeutic diet and usual diet

Difference in change-from-baseline percentage (%) of CD8+ (cluster of differentiation 8) T cells between therapeutic diet and usual diet

Difference in change-from-baseline percentage (%) of monocytes between therapeutic diet and usual diet

Inclusion Criteria: Subjects with aged older than 20 years, ESKD undergoing maintenance dialysis for more than three months, having adequate dialysis, serum intact parathyroid hormone less than 800 pg/mL and good dietary compliance Exclusion Criteria: Patients who meet any of the following criteria will be excluded from the study: Serum albumin level less than 2.5 g/dL Hospitalization within the past 4 weeks Prebiotics, probiotics, symbiotics or antibiotics use within the past 4 weeks History of psychiatric disorders Having mental retardation Those who dislike of the study meals Soft diet requirement Vegetarian

Individual-level deidentified participant data will be made available by the corresponding author of the paper upon request by email. The data will be available for 3 years after formal publication.

The data will become available after completing the study for 1 year and for 3 years after formal publication.

Tsai WC, Wu HY, Peng YS, Hsu SP, Chiu YL, Yang JY, Chen HY, Pai MF, Lin WY, Hung KY, Chu FY, Tsai SM, Chien KL. Short-Term Effects of Very-Low-Phosphate and Low-Phosphate Diets on Fibroblast Growth Factor 23 in Hemodialysis Patients: A Randomized Crossover Trial. Clin J Am Soc Nephrol. 2019 Oct 7;14(10):1475-1483. doi: 10.2215/CJN.04250419. Epub 2019 Sep 13.

Tsai WC, Wu HY, Peng YS, Hsu SP, Chiu YL, Chen HY, Yang JY, Ko MJ, Pai MF, Tu YK, Hung KY, Chien KL. Effects of lower versus higher phosphate diets on fibroblast growth factor-23 levels in patients with chronic kidney disease: a systematic review and meta-analysis. Nephrol Dial Transplant. 2018 Nov 1;33(11):1977-1983. doi: 10.1093/ndt/gfy005.