Protein, phosphate intake and serum phosphate values in peritoneal dialysis patients

Author(s): Maša Škrlep, Bojan Knap

Introduction: Evaluation of dietary intake of patients on peritoneal dialysis is necessary for understanding the elevated phosphate levels, as well as protein intake monitoring, which struggles to meet current dietary guidelines.

Methods: The single-center observational study. 20 patients on peritoneal dialysis were randomly selected. A food propensity questionnaire has been carried out with three unannounced 24-hour dietary recalls per participant through a web-based application. Body composition has been measured with bio impedance spectroscopy. Continuous variables between normal values and of study values were compared using paired t-tests and Wilcoxon signed ranks test. A two-tailed P value <0.05 was considered statisticallx significant.

Results: Average caloric intake of 20 patients was (25.6 ± 6.7) kcal/kg body mass (BM)/day, average protein intake was (0.9 ± 0.3) g/kg BM/ day. They were inadequate according to the dietary recommendations for dialysis patients on peritoneal dialysis (PD). Average intake of micro-nutrients (K, P, Na) corresponds to the recommendations for dialysis patients which is surprisingly according to high levels of serum phosphorus ((1.6 ± 0.4) mmol/L) and intact parathyroid hormone ((450 ± 393) ng/L). Phosphorus intake was moderately correlated with the dietary energy intake (p = 0.0001). The correlation between dietary phosphorus intake and serum phosphorus was insignificant (p = 0.509). The correlation between dietary phosphorus to dietary protein ratio was 0,159. In dietary report showed 60 % of animal protein intake and 40 % of plant protein intake. Dietary phosphorus and protein intake ratio was (16 ± 3.6) mg/g. Inorganic phosphate from additives were not detected in all item because of lack of information in database.

Conclusion: Food databases are needed in order to provide optimal nutrition. Patients still lack proper nutritional knowledge, hence new educational technics and help will be needed in the future. Detecting inorganic phosphate is difficult due to lack of information in databases and specific bioavailability and absorption.