This study is an unblinded, open-label, parallel-group randomized controlled trial evaluating the effect of a plant-focused diet on the nutritional status of malnourished patients undergoing PD. This study will be conducted over 6 months, alongside each participants’ routine PD clinic visits. Patients and the public were not involved in the design, conduct, reporting, or dissemination plans of this study.

This study protocol is adapted from a similar ongoing clinical trial involving patients with CKD with diabetes mellitus in the United States [16]. Figure 1 shows a diagram outlining the research flow. The study begins with participant screening, recruitment, and baseline assessment conducted on the same day. Following baseline assessment, participants are then randomized into either the intervention group receiving a plant-focused dietary intervention or the control group receiving a standard renal dietary intervention.

A 2-week familiarization phase is implemented immediately after randomization as part of the intervention period. During this phase, participants begin following their assigned dietary intervention and receive additional guidance and closer monitoring to support early adaptation and adherence. This phase is intended to facilitate understanding of the dietary protocol and to identify and address potential challenges early, rather than to assess eligibility or introduce selection bias.

Participants from both groups are instructed to continue the assigned dietary intervention for 6 months. Key outcome assessments are conducted at baseline (0 months), midpoint (3 months), and end line (6 months). Data collected will be analyzed for subsequent report writing and publication.

The intervention and study procedures, including screening, recruitment, data collection, and intervention delivery, will be conducted by a registered dietitian. Health care staff at the study site will assist with clinical procedures such as blood collection.

Participants will be recruited from the nephrology unit at a tertiary care hospital in Klang, following approval from the research ethics committee. A second center may be considered to meet recruitment targets.

The sample size was calculated using the standard formula for comparing 2 independent means in a parallel-group design using several assumptions.

On the basis of previous studies in dialysis populations, an estimated SD of 5 g/L was used to account for heterogeneity and to avoid underestimation of sample size. Notably, studies by Kalantar-Zadeh et al [17] and Rambod et al [18] reported serum albumin SDs ranging from 1.9 to 4.4 g/L, while a study by Limwannata et al [19] reported an SD of 5.0 g/L.

A clinically meaningful difference (δ) of 3 g/L (0.3 g/dL) was selected as it is consistent with differences in serum albumin levels observed across dialysis populations in previous studies. For instance, variations of 0.3 to 0.4 g/dL are observed between cohorts reported in studies by Rambod et al [18] and Limwannata et al [19]. Additionally, serum albumin is a well-established predictor of morbidity and mortality in patients undergoing dialysis, and even modest changes are considered clinically relevant in reflecting improvements in nutritional status [17].

Using the formula mentioned below, a 2-sided significance level of.05 (Zα/2=1.96) and 80% power (Zβ=0.84) were used to calculate the sample size. As a result, a minimum of 44 participants per group was required. After accounting for an anticipated 10% dropout rate, the sample size was rounded up to 50 participants for each group, with a total sample size of 100 participants. As repeated measurements will be conducted at baseline, 3 months, and 6 months, the calculated sample size is considered conservative.

The sample size was calculated using the standard formula for comparing 2 independent means in a parallel-group design, as shown below:

Where n is the sample size per group, Zα/2 is the standard normal deviate for a 2-sided significance level (1.96 for α=.05), Zβ is the standard normal deviate for power (0.84 for 80% power), σ is the SD, and δ is the expected difference between groups.

Screening of participants will be conducted by reviewing the patient registry at the identified PD clinic to identify potential participants. Medical records will then be used to assess eligibility, and those who do not meet the criteria, as shown in Textbox 1, will be excluded. Eligible participants will be contacted via phone to receive a brief explanation of the study, and those who have expressed interest in participating or provided verbal consent will be scheduled for a physical screening visit at the clinic. During the screening visit, the participants will be provided with the participant information sheet and informed consent form, available in both Malay and English languages. They will be given ample time to review the study details before providing written consent, and only participants who have signed the consent form will be assigned a screening ID.

Throughout the 6-month study period, the participants will be monitored for adherence and motivation. The specific criteria for withdrawal and dropout are as follows: (1) missing ≥50% of follow-up visits during the 6-month study, (2) <50% compliance at 3 consecutive monthly review points based on the dietary compliance scoring system (scoring criteria are informed by clinical relevance, current dietary guidelines, and prior literature), (3) failure to comply with the study protocol, (4) voluntary withdrawal from the study, and (5) identification of a clinical condition requiring intervention or likely to affect study outcomes.

To manage dropouts, participants who withdraw, fail to meet compliance, or are lost to follow-up will be seen by an investigator. Reasons for failure to comply with the study protocol will be documented. Data collected up to the point of withdrawal will be retained and analyzed unless requested otherwise by the participant. Participants withdrawn from the study will not be replaced, as the sample size calculation includes an allowance for dropouts.

Participants will be randomly assigned using the Random Allocation Software (version 2.0; developed by Mahmood Saghaei, Isfahan University of Medical Sciences) to either the intervention group (plant-focused dietary intervention) or the control group (standard renal dietary intervention) [20]. The software will generate allocation codes (1 for intervention and 2 for control) based on block randomization with a 1:1 ratio and a block size that is a multiple of 4. This study is unblinded, and the allocation sequence will be accessible to the researcher assigning participants.

The control group will follow a standard renal diet and be encouraged to maintain their usual dietary and physical activity patterns, with guidance to ensure that at least 50% of their total protein intake comes from high biological value animal-based sources. The standard renal diet was chosen as comparator as it reflects the current clinical practice. In contrast, the intervention group will follow a plant-focused dietary pattern that emphasizes plant-based foods, such as fruits, vegetables, legumes, whole grains, nuts, seeds, and plant oils, with minimal reliance on animal-based products. Participants in the intervention group will be required to consume plant-focused meals for most of their daily meals. For example, those consuming 3 meals per day must ensure that at least 2 out of the 3 meals are plant based, while those consuming 4 meals per day must ensure that at least 3 out of the 4 meals are plant based. The remaining meal or snack may include either plant- or animal-based foods to support flexibility and adherence.

Participants in both groups will receive individualized dietary counseling at each data collection point (baseline, 3 months, and 6 months). In addition, participants are also provided with educational pamphlets and 14-day structured meal plans that incorporate natural food sources and culturally appropriate meal choices. Meal plans for both groups are developed in accordance with the Malaysian Medical Nutrition Therapy Guidelines for Chronic Kidney Disease and the Kidney Disease Outcomes Quality Initiative Clinical Practice Guidelines for Nutrition in CKD [7,21]. Throughout the study, participants will continue to receive standard medical care, with no specific concomitant care prohibited.

The parameters assessed at each participant visit, from screening through the 6-month study duration, are summarized in Table 1. Data will be collected through various questionnaires and standardized procedures. All questionnaires used are freely and publicly accessible.

Postdialysis weight, height, BMI, TSF, and mid–upper arm circumference will be measured using standard protocols. MAMC will be calculated as MAMC=mid–upper arm circumference−(π×TSF). Body composition will be assessed using bioelectrical impedance analysis where available.

Laboratory parameters (renal, lipid, glucose, inflammation, dialysis adequacy, and protein intake) will be extracted from hospital records. hs-CRP will be analyzed externally using 10 mL fasting blood samples collected by trained staff.

Nutritional and inflammatory status will be assessed using the MIS (range 0-30). This tool has been locally validated, with a score of <5 indicating normal status and ≥5 indicating malnutrition [5].

Participants will complete a 3-day food diary monthly (2 weekdays and 1 weekend). At the first clinic visit, participants will receive training on how to accurately record only foods and beverages consumed using household measurements and a colored food album to assist with portion size estimation. Dietary intake data will then be analyzed using Nutritionist Pro (version 5.1.0; Axxya Systems [22]) using information from the Nutrient Composition of Malaysian Foods and Singapore Food Composition Book (Ministry of Health Singapore [23,24]).

Dietary adherence will be evaluated using a binary compliance scoring system, as detailed in Tables 2 and 3. Although arbitrarily set, the scoring categories were informed by clinical relevance, current dietary guidelines (medical nutrition therapy and Kidney Disease Outcomes Quality Initiative), and prior literature on compliance assessment in chronic disease populations [7,21,25].

Each daily dietary record is scored out of a maximum of 7 points. A “1-day” record refers to a single 24-hour dietary record, whereas a “3-day” record represents the aggregation of three separate daily dietary records collected from participants. The total score for each 3-day dietary assessment therefore ranges from 0 to 21 points. Total scores are calculated by summing the scores from each daily record. A total score of ≥50% (≥10.5/21) indicates adequate dietary compliance, whereas scores <50% indicate poor compliance. To ensure feasibility and acceptability, the dietary compliance scoring system will be pilot tested with participants during the first 2 weeks of the study period.

Appetite will be assessed using the validated Appetite and Food Satisfaction Questionnaire, which scores appetite and satisfaction from 0 to 18 (lower=better appetite) [26].

QOL will be measured using the World Health Organization Quality of Life-BREF, comprising 26 items across 4 domains (physical, psychological, social, and environmental) [27]. Scores are converted to a 0 to 100 scale, with higher scores reflecting better QOL.

Physical activity will be measured using the short form of the International Physical Activity Questionnaire [28]. Results will be expressed in Metabolic Equivalent of Task minutes per week. Physical function will be assessed using the Short Physical Performance Battery, a well-established, standardized instrument that has been extensively used and validated in dialysis populations worldwide, with higher total scores indicating better physical function [29,30]. Handgrip strength will be measured using a Jamar dynamometer, with the mean of 3 consistent trials recorded.

A validated 34-item questionnaire will assess dietary knowledge (12 items), attitude (7 items), and practice (15 items) [31]. Higher scores reflect better understanding and adherence to renal diet principles.

Sociodemographic and medical history are collected via a structured interview guided by a general questionnaire covering demographic data, socioeconomic status, medical and dialysis history, medications, physical activity, and allergies.

This study has obtained ethics approval from the Universiti Kebangsaan Malaysia Research Ethics Committee (JEPUKM; JEP-2025-812). The study will be conducted in accordance with the Declaration of Helsinki, Malaysian Good Clinical Practice Guidelines, and institutional policies. Any protocol deviations will be reported to the ethics committee as required. Adverse events will be monitored throughout the study period and followed up as appropriate. Participants will continue to receive standard clinical care throughout the trial.

A data monitoring committee is not required for this study due to the low-risk nature of the intervention. No interim analyses or stopping guidelines are planned due to the nature and duration of the study. Trial conduct will be monitored by the research team to ensure adherence to the study protocol. No formal external monitoring is planned due to the low-risk nature of the study.

Eligible participants will receive a participant information sheet and informed consent forms, available in Malay and English. Written consent will be obtained before any study-related procedures. If written consent is not possible, oral consent will be documented in the presence of an independent witness. Participation is voluntary, and participants may withdraw at any time without affecting their standard care. Data collected up to withdrawal will be retained unless otherwise requested.

All participant data will be anonymized and handled in compliance with the Malaysian Personal Data Protection Act 2010 [32]. Data will be stored on drives accessible only to authorized personnel and retained for at least 2 years after study completion before secure disposal. Results will be disseminated through peer-reviewed publications, conference presentations, and individual summaries shared with participants where appropriate. No personal identifiers will appear in any publications. Deidentified data will not be publicly available due to ethical and privacy considerations.