---
title: "Dietitian-led nutritional counseling for constipation in Parkinson’s disease: NUTRI-GUT-PD trial p"
id: "plos-one-11-dietitian-led-intervention-to-manage-constipation-in-parkinson-s-disease-study"
canonical_url: "https://medichelpline.com/clinical-feed/plos-one-11-dietitian-led-intervention-to-manage-constipation-in-parkinson-s-disease-study"
content_type: "clinical_feed_article"
specialty: "Neurology"
source_name: "PLOS ONE (Medicine)"
source_url: "https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0354608"
published_at: "2026-07-27T14:00:00.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Dietitian-led nutritional counseling for constipation in Parkinson’s disease: NUTRI-GUT-PD trial p
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/plos-one-11-dietitian-led-intervention-to-manage-constipation-in-parkinson-s-disease-study
- **Specialty:** [Neurology](https://medichelpline.com/clinical-feed/neurology.md)
- **Primary Source:** PLOS ONE (Medicine)
- **Source URL:** [Original Journal Publication](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0354608)
- **Published At:** 2026-07-27T14:00:00.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- This article describes the study protocol for NUTRI-GUT-PD, a 90-day parallel-group randomized controlled superiority trial testing a **dietitian**-led nutritional counseling intervention versus usual care to manage **constipation** in people with **Parkinson’s Disease (PD)**. - The trial will enroll 54 outpatients with PD without dementia who meet Rome IV criteria for functional constipation and are on stable levodopa for ≥3 months; recruitment occurs at a single center in Brazil (Hospital de Clínicas de Porto Alegre). - Baseline assessments include demographics, anthropometry, sarcopenia indicators, neurological evaluation, Constipation Scoring System (CSS), three 24-hour dietary recalls, stool sample collection for fecal **gut microbiota** analysis, and a stool diary for bowel movement frequency. - Participants are randomized to usual care (control) or to the intervention: one in-person dietitian consultation, bi-weekly follow-up phone calls, and an individualized diet plan addressing healthy eating, food processing, fiber and fluid intake, and **levodopa**–diet interactions over 90 days. - The primary outcome is change in weekly bowel movement frequency from baseline to day 90 measured by the stool diary. Secondary outcomes include CSS scores, fecal microbiota composition, macronutrient distribution, diet quality, body composition, and sarcopenia indicators. - The protocol follows SPIRIT guidelines and includes trial registration (NCT07213856). No datasets have yet been generated; data will be made available upon study completion. Funding came from CAPES; authors report no competing interests. - Rationale: constipation is a common, often under-treated non-motor symptom in PD, associated with altered gut motility, dysbiosis, and possible contributions to PD pathophysiology; dietary management is promising but evidence is limited and may risk nutritional complications if not supervised by a dietitian. - The investigators hypothesize the dietitian-led intervention will produce greater improvements in bowel frequency, constipation scores, gut microbiota profile, and diet quality than usual care.
## Clinical Analysis & Structured Key Points
Dietitian-led intervention to manage constipation in Parkinson’s disease: Study protocol for a parallel-group randomized controlled trial (NUTRI-GUT-PD) | PLOS One Browse Subject Areas ? Click through the PLOS taxonomy to find articles in your field. For more information about PLOS Subject Areas, click here . Article Authors Metrics Comments Media Coverage Peer Review Reader Comments Figures Figures Abstract Background Constipation is a frequent non-motor symptom in Parkinson’s Disease (PD). Standard care includes dietary and lifestyle guidance or the use of laxatives. Diet represents a promising non-pharmacological approach, but its management in PD is complex and goes beyond simple dietary recommendations. This study protocol aims to examine whether nutritional counseling delivered by a dietitian is more effective than usual care in reducing constipation symptoms in PD patients. Methods This 90-day randomized controlled superiority trial uses a parallel-group design. A total of 54 outpatients with PD without dementia and fulfilling the Rome IV criteria for functional constipation will be included. Baseline assessments comprise demographics, nutritional evaluation (anthropometric measurements and sarcopenia indicators), neurological assessment, and the Constipation Scoring System (CSS) scores. Participants will perform stool sample collection for microbiota analysis and will be requested to complete three 24-hour dietary recalls over the subsequent week. After baseline, participants will be randomly allocated to either the control group (usual care) or the intervention group (nutritional counseling delivered by a dietitian). At the first study visit, participants will deliver the stool sample and dietary recalls. The intervention will last for 90 days and will include one in person consultations and bi-weekly follow-up phone calls. Nutritional counseling will address four main topics: healthy eating, food processing, fiber and fluid intake, and levodopa interactions with diet. In addition, participants in the intervention group will receive an individualized diet plan. All baseline assessments will be repeated at the 90-day endpoint. The primary outcome is the change in weekly bowel movement frequency from baseline to day 90, measured through the stool diary. Secondary outcomes include CSS, changes in fecal gut microbiota, macronutrient distribution, diet quality, body composition and sarcopenia indicators. Trial registration number: NCT07213856. Citation: Brendler JH, da Silva KY, Dall’Alba V, Martins AF, Teixeira-dos-Santos D, Schuh AFS, et al. (2026) Dietitian-led intervention to manage constipation in Parkinson’s disease: Study protocol for a parallel-group randomized controlled trial (NUTRI-GUT-PD). PLoS One 21(7): e0354608. https://doi.org/10.1371/journal.pone.0354608 Editor: Zehra Batu, Necmettin Erbakan Üniversitesi: Necmettin Erbakan Universitesi, TÜRKIYE Received: February 3, 2026; Accepted: July 2, 2026; Published: July 27, 2026 Copyright: © 2026 Brendler et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: Since this manuscript is a Study Protocol, no datasets have been generated or analysed yet. As per PLOS guidelines for Study Protocols, all relevant data will be made available upon study completion. Funding: This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) (Finance Code 001). The doctoral scholarship was awarded to JHB. Funder website: https://www.gov.br/capes This funding represents general PhD funding and the funder had no role in the study design; data collection, analysis, or interpretation; decision to publish; or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Introduction Parkinson’s Disease (PD) has seen a rapid increase in its incidence and prevalence worldwide over the last decades, in an almost pandemic manner [ 1 ]. This neurodegenerative disease can span decades and tends to accumulate disabilities over time. For people living with PD, the consequences are significant, and for society, the socioeconomic burden is straining [ 2 ]. At this time, there is still no therapy that can slow down disease progression; therefore, optimal treatment should include a multidisciplinary approach with optimized symptomatic pharmacological therapy associated with non-pharmacological strategies [ 3 ]. Constipation is one of the most prevalent non-motor symptoms in patients with PD, affecting from 20% to 81% of individuals [ 4 ], and contributing to a reduced quality of life [ 5 ]. This symptom is linked to alterations in gut motility and gastrointestinal dysregulation [ 6 ], which can precede motor symptoms by up to two decades [ 7 ], and it is a prodromal characteristic of the disease. The brain-gut axis connects the enteric nervous system, gut microbiota and central nervous system in a communication pathway involving neural, immune, and endocrine mechanisms [ 8 , 9 ]. The prolonged intestinal transit time in these patients can lead to gut microbiota dysbiosis. Dysbiosis in PD is characterized by reductions in beneficial short-chain fatty acid (SCFA)-producing bacteria and elevations in pro-inflammatory microbial species. These alterations are linked to increased intestinal permeability, which allows bacterial endotoxins such as lipopolysaccharides to enter the bloodstream, intensifying neuroinflammation and dopaminergic neuronal degeneration [ 8 , 10 ]. The relationship between gut dysbiosis and constipation in PD is bidirectional and complex. Recent evidence demonstrates that specific gut microbiota alterations may have a causal effect on the development of constipation, and that PD pathophysiology may drive the development of constipation indirectly by altering these specific bacterial taxa [ 11 ]. Large-scale metagenomic studies revealed that over 30% of bacterial species, genes, and pathways are altered in PD, with depletion of SCFA-producing genera such as Faecalibacterium and Roseburia, and enrichment of pro-inflammatory taxa including Collinsella and Akkermansia [ 12 , 13 ]. This positions constipation not merely as a symptom but as a potential early biomarker and therapeutic target in PD. Despite its prevalence and relevance, constipation in PD is often overlooked, and the absence of robust evidence has led to a lack of a standardized approach in international guidelines [ 14 ]. Usual care typically relies on general advice regarding fiber intake and lifestyle modifications provided by the clinician, or on the use of laxatives [ 15 ]. The available treatment options remain suboptimal for managing constipation symptoms in the majority of patients [ 16 ]. Focusing on dietary interventions for constipation in PD, the current literature does not provide sufficient evidence to support strong recommendations. The Mediterranean diet may have beneficial effects on the gut microbiota [ 17 ], and has been effective in reducing PD-related constipation symptoms, however those findings were comparable to those achieved with standard care [ 18 ]. The Mediterranean approach was associated with increased fiber intake and reduced intestinal inflammation [ 18 ], though its feasibility in underdeveloped countries remains a concern. Psyllium fiber supplementation demonstrated positive effects on stool frequency and weight but did not alter colonic transit, this evidence is limited to a small sample of seven participants [ 19 ]. Dietary changes in PD patients without expert guidance may pose risks of weight loss, malnutrition, sarcopenia, and worsening abdominal symptoms [ 20 ]. Diet management in PD is multifaceted and extends beyond simple dietary advice, encompassing the management of several non-motor symptoms and nutritional complications, including constipation [ 21 ]. Nutritional interventions led by dietitians have demonstrated superior effects compared to usual care in randomized controlled trials (RCTs) and meta-analyses, particularly in improving metabolic and cardiovascular outcomes, nutritional status, and diet quality [ 22 – 24 ]. Given the importance of nutritional management in PD and the lack of RCTs evaluating structured dietary interventions in this population, further investigation is warranted. Therefore, the primary objective is to investigate whether individualized nutritional counseling, delivered by a dietitian, is more effective than usual care in increasing the frequency of bowel movements in patients with PD. We hypothesize that the intervention group will present greater improvement in constipation assessments, gut microbiota profile, and diet quality. Methods This protocol is reported following the SPIRIT reporting guidelines. Trial design This study is a randomized, controlled, superiority trial with a parallel-group design and a duration of 90 days. It will be conducted at the Hospital de Clínicas de Porto Alegre (HCPA), Brazil. The study targets adults diagnosed with PD without dementia who are experiencing constipation. Participants will be recruited at the Movement Disorders Research Group outpatient clinic of HCPA. Eligibility criteria Adults with a prior diagnosis of PD, confirmed by a neurologist according to the Movement Disorders Society clinical diagnostic criteria [ 25 ], and receiving a stable dose of levodopa for at least 3 months will be included. In addition, participants must report at least two criteria defined by the Rome IV protocol for functional constipation [ 26 ]. Exclusion criteria include: (1) atypical or secondary parkinsonism, (2) Hoehn & Yahr stage greater than 3, (3) severe neurological or psychiatric disorders that could interfere with study procedures, (4) dementia diagnosis, (5) diagnosis of active cancer, chronic obstructive pulmonary disease, heart failure, or chronic kidney disease, (6) history of gastrointestinal neoplasms, inflammatory bowel disease, or gastrointestinal surgery (7) constipation secondary to conditions such as hypothyroidism or diabetes mellitus, (8) recent opioid use, (9) use of probiotics or antibiotics within the past 30 days, or within the past 90 days if administered during hospitalization, (10) continuous daily laxative use in the last eight weeks, (11) uses a texture-modified diet, requires feeding assistance, or presents chewing/swallowing limitations, defined as not being classified as FOIS level 7 (total oral intake with no restrictions), (12) enteral or parenteral nutrition, or (13) ongoing nutritional counseling within the last 3 months. Recruitment Participants will be recruited from a database of individuals who participated in a prior study. Individuals meeting the eligibility criteria will be invited to participate in the NUTRI-GUT-PD study, either by phone or during their routine outpatient visits. Those who agree to participate will provide written informed consent, after which the baseline visit will be scheduled to initiate study procedures. Randomization The randomization sequence will be generated by an independent statistician using the Sealed Envelope software. Randomization will be stratified by sex (male/female). Allocation concealment will be ensured through the REDCap electronic data capture tools. Participants will be randomized sequentially in the order that they provide informed consent. Group assignment will be disclosed to participants at D0. Initial baseline assessments will occur before randomization, eliminating the need for blinding at this stage. Outcome assessors, including dietitians responsible exclusively for assessments and the neurologist performing clinical evaluations at baseline and D90, as well as microbiota sequencing professionals and the statistician, will be blinded to group allocation. Dietitians responsible for delivering the intervention will not be blinded, due to the nature of the counseling. Sample size A sample size of 48 subjects (24 per group) was calculated to determine whether a minimum difference of 1 bowel movement/week exists between the mean weekly bowel movements of the intervention and control groups at the final time point (D90) of this repeated measures study protocol. Accounting for a 10% attrition rate due to potential losses and refusals, the total sample size was adjusted to 54 subjects (27 per group). The calculation considered a power of 80%, a significance level of 5%, and standard deviations of 1.15 and 1.21 bowel movements/week for the intervention and control groups, respectively [ 18 ], as well as a 90% retention rate at time points 2 and an exchangeable correlation matrix with a correlation of 0.5. This calculation was performed using the PSS Health online tool [ 27 ]. Outcomes Primary outcome. The primary outcome of this study protocol is change in weekly bowel movements measured through the stool diary, comparing between-group differences at endpoint (D90). Secondary outcomes. Secondary outcomes will evaluate the following from baseline (D0) to the end point (D90): Proportion of participants achieving a clinically meaningful improvement, defined as an increase of >1 bowel movement per week; Changes in total scores of the Constipation Scoring System (CSS); Alterations in fecal gut microbiota composition, specifically measuring alpha diversity (within-sample richness), beta diversity (between-sample composition), and differential abundance at the species level; Changes in macronutrient distribution derived from three 24-hour dietary recalls; Changes in the Screener-Nova scores, regarding food processing; Changes in Bioelectrical Impedance Analysis (BIA) and anthropometric measurements; Changes in sarcopenia assessments. Participant timeline The participant timeline is presented in Fig 1 . After eligibility screening and informed consent, participants will complete baseline assessments and will then be randomized to either the control or the intervention group. The intervention period will last 90 days. Download: PNG larger image TIFF original image Fig 1. Participant schedule of enrolment, interventions, and assessments. IPAQ-SF: International Physical Activity Questionnaire- Short Form; CSS: Constipation Scoring System; FFQ: Food Frequency Questionnaire; BIA: Bioelectrical Impedance Analysis; MNA-SF: Mini Nutritional Assessment – Short Form. *All visit days are ± 3 days. a Patients will receive stool collection kits one week before visit days, allowing them to bring the samples on the visit day for analysis. b Two 24-hour dietary recalls by phone in the week prior and one in-person recall at the study visit. https://doi.org/10.1371/journal.pone.0354608.g001 At the time of submission, the study is in the pre-recruitment phase. Participant recruitment is expected to begin in March 2026 and to be completed by July 2026. Each participant will undergo a 3-month intervention period, and data collection is expected to be completed by November 2026. Data analysis is planned between December 2026 and January 2027, and study results are expected in early 2027. Study findings will be disseminated through peer-reviewed publications and conference presentations. Data collection The study will include three in-person visits at baseline, D0, and D90, with a phone contact on D45. In addition, participants will receive phone calls every 15 days to promote adherence to the intervention, address potential issues, and inquire about intestinal symptoms. The assessments planned for each visit are summarized in Fig 2 and detailed below. Download: PNG larger image TIFF original image Fig 2. Study Design NUTRI-GUT-PD. BIA: Bioelectrical Impedance Analysis; 24h DRs: Three 24h Dietary Recalls. Figure created by the author (2025). https://doi.org/10.1371/journal.pone.0354608.g002 Considering the complexity of the proposed assessment battery and the inherent mental and physical fatigue associated with the neurodegenerative condition, several strategies will be utilized to promote participant retention and adherence throughout the trial. Participants will be offered a ± 3day window for all scheduled visits and phone calls. Caregivers will be actively encouraged to attend study visits and assist with data collection, and provide logistical support to the participant. Lastly, to facilitate compliance, scheduled communication via text message or telephone calls will be established. Encompassing confirmation of visit appointments, reminders regarding BIA orientation, daily prompts to complete the stool diary, and reminders to collect and bring the stool sample and the completed diary to the scheduled visit. Sociodemographic data. A standardized questionnaire including age, sex, education, self-reported ethnicity, and household income will be used to collect sociodemographic data at baseline. Neurological evaluation. Medical history, covering disease duration, age at diagnosis, comorbidities, and use of Deep Brain Stimulation (DBS), will be collected at baseline. Disease severity and duration will be assessed using the Hoehn and Yahr staging scale. Information on medication use will be collected at baseline and on D90, including the daily levodopa equivalent dose (LEED) and any concomitant treatments or constipating medications. The study neurologist will perform a clinical assessment at baseline and D90, including the following validated instruments: MDS-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) [ 28 ]: Comprehensive assessment of PD severity across motor and non-motor symptoms. The MDS-UPDRS consists of four parts with a total of 65 items, each rated on a 5-point scale (0 = normal, 1 = slight, 2 = mild, 3 = moderate, 4 = severe). Montreal Cognitive Assessment (MoCA) [ 29 ]: A cognitive screening that evaluates attention, executive functions, memory, language, visuospatial abilities, abstraction, calculation, and orientation. The total score ranges from 0 to 30, with higher scores indicating better cognitive performance. The cut-off score of ≤25 will be used to indicate possible cognitive impairment. Swallowing Disturbance Questionnaire (SDQ) [ 30 ]: A 15 items screening questionnaire designed to identify symptoms of dysphagia. The instrument assesses the frequency of swallowing-related difficulties in daily life, with higher scores indicating greater severity of swallowing disturbances. International Physical Activity Questionnaire- Short Form (IPAQ-SF) [ 31 ]: A 7-item instrument that assesses physical activity over the last 7 days. Results are calculated in MET-minutes/week by multiplying the activity’s MET by its duration and frequency. Based on these scores, individuals are classified into three levels: Low (failing to meet other criteria), Moderate (total from any activity ≥600 MET-min/week or specific frequency thresholds), and High (vigorous activity reaching ≥1500 MET-min/week or a total of ≥3000 MET-min/week). This assessment will be repeated at mid-point (D45) through phone contact by the study dietitian. Constipation assessment. Constipation will be evaluated using two instruments to capture both subjective and objective aspects of bowel function. All participants will receive a stool diary to be completed daily. This tool will be used to monitor the progression of constipation symptoms throughout the study period. The following items will be recorded: Was evacuation present today? Weekly bowel movement frequency will be calculated accordingly. What was the stool consistency? Assessed using the Bristol Stool Form Scale. Types 1–2 will be classified as hard stools and reported as the weekly percentage of total evacuations. Was there a sensation of straining? Responses (“Yes” or “No”) will be summarized as weekly percentages. Was the evacuation incomplete? Responses (“Yes” or “No”) will be summarized as weekly percentag
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