Inadequate dietary protein intake is well-known cause of hypoalbuminemia in dialysis population. Protein loss into dialysate and increased catabolic state due to uremic milieu or inflammation worsened hypoalbuminemia, hence high protein diet is recommended in patients on peritoneal dialysis (PD). The recommendations from K/DOQI clinical practice guidelines for the amount of daily protein intake is based on expert opinion and the optimal daily protein intake in PD patients is not known. The investigators hypothesize that higher dietary protein intake has a greater beneficial effect on nutritional status in hypoalbuminemic PD patients. In particular, 1.5 g/kg protein intake provides a better beneficial effect than 1.2 g/kg protein intake.

Hypoalbuminemia is common and is strongly associated with an increased risk for mortality in patients with end-stage kidney disease (ESKD). Inadequate dietary protein intake is well-known cause of hypoalbuminemia in dialysis population. Protein loss into dialysate and increased catabolic state due to uremic milieu or inflammation worsened hypoalbuminemia, hence high protein diet is recommended in PD patients. Although there is an increased daily calorie intake from absorption of dialysate glucose concentration, hypoalbuminemia ensues in a substantial number of PD patients. There is concern that a disproportionately increasing calorie intake from dialysate glucose with no change in dietary protein intake causes weight gain which in turn worsens sarcopenic obesity in PD patients. Achieving adequate dietary protein intake should be the priority in the management of hypoalbuminemia. It is feasible for PD patients to increase dietary protein intake through protein supplements. Among nutritional supplements, whey protein has several positive effects on carbohydrate metabolism, muscle building, immune function, and human health in various areas of disease, supported by well-performed studies. There are limited data available regarding the effects of nutritional counseling and whey protein supplements on the nutritional, body compositional status and immune function of PD patients with hypoalbuminemia. The recommendations from K/DOQI clinical practice guidelines for the amount of daily protein intake is based on expert opinion and the optimal daily protein intake in PD patients is not known.

The aims of the study are to investigate the optimal dietary protein intake and to examine the effects of whey protein supplement on the change of nutritional, body composition and immune function in PD patients with hypoalbuminemia. Specifically, the investigators will compare the effect of nutritional counseling (1.2 g/kg protein intake) with that of nutritional counseling and whey protein supplement (1.5 g/kg protein intake) regarding the changes of nutritional, body composition parameters and immune function in PD patients. This is a quality improvement program to cope with the fact that the proportion of hypoalbuminemic PD patients sometimes does not meet the requirements set by Joint Commission of Taiwan, and to improve the nutritional status of PD patients in a feasible way of daily clinical practice.

The investigators are going to conduct a randomized, controlled trial with cross-over design. Subjects with ESKD undergoing maintenance PD for more than three months, adequate dialysis, and hypoalbuminemia will be recruited. Those with non-dietary cause of hypoalbuminemia including untreated fluid overload, uncorrected metabolic acidosis, having active infection or inflammation, hospitalization within the past 4 weeks, having gastrointestinal bleeding, those who cannot cooperate with the dietary record, those who have poor adherence to whey protein consumption, history of psychiatric disorders and having mental retardation will be excluded. Participants will receive nutritional counseling with whey protein supplement or nutritional counseling alone for 3-month period, separated by 3-month washout period. The study outcome measures are difference in change-from-baseline nutritional, body composition parameters and immune function between the two study periods.

Inclusion Criteria:

1. Aged greater than or equal to 20 years
2. Having end-stage kidney disease and having undergone maintenance PD for more than three months
3. Having adequate dialysis (weekly Kt/V greater than or equal to 1.7)
4. Serum albumin levels lower than 4.0 g/dL, measured by bromocresol green assay

Exclusion Criteria:

1. Untreated fluid overload
2. Uncorrected metabolic acidosis
3. Having active infection or inflammation
4. Hospitalization within the past 4 weeks
5. Having gastrointestinal bleeding
6. those who cannot cooperate with the dietary record
7. those who have poor adherence to whey protein consumption
8. History of psychiatric disorders
9. Having mental retardation

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.

Data will be made available by the corresponding author of the paper upon request by email.

Laboratory technicians who assess the study outcomes will be masked