A Phase 1 interventional study of Prebiotic fiber bar in PARKINSON DISEASE (Disorder), sponsored by Stanford University. Not yet recruiting at 1 site in United States. Open to participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-11-03.
Sponsored by Stanford University · Phase 1, Interventional, and Basic science
Among 19 studies in Parkinson Disease by Stanford University — 10 open to participants now, 10 under way, none of them phase 3. Parkinson Disease · Stanford University.
Among the 19 studies in Parkinson Disease by Stanford University, this one has the largest planned enrollment, is one of 3 that started in 2026, is one of 2 in phase 1, and was the 19th registered.
4,573 studies on the registry are indexed under Parkinson Disease; 1,086 are open to participants now.
This study's planned enrollment of 50 is above the median of 40 across 3,353 interventional studies indexed under Parkinson Disease.
Browse Parkinson Disease studies →10 of the 19 studies in Parkinson Disease by Stanford University are open now, in 1 country. Each count lists the studies.
Of the 748 Parkinson Disease studies recruiting now, 311 (42%) set no upper age limit and 127 (17%) stop at 75 or younger; 63 take children under 18; 189 take healthy volunteers.
This study: 18 Years and older · all sexes · healthy volunteers too.
The full table on the hub →19 studies; the count open now beside each. This study's row is marked.
First in 2009; this study’s year is marked. 3 started in 2026.
Median enrollment 20 across the 19 interventional studies. Of the 9 that completed or were terminated, 8 (89%) have results posted.
Stanford University is the lead sponsor of 2,168 studies on the registry; 431 are open to participants now.
Of its 267 completed or terminated interventional studies of FDA-regulated products, 207 (78%) have results posted.
10 of the studies in Parkinson Disease by Stanford University that are under way reach primary completion within a year, 0 of them phase 3. Phase 3 first, then by date:
| Study | Primary completion |
|---|---|
| NCT05504902Stanford UniversityVibrotactile Coordinated Reset for the Treatment of Advanced Parkinson's Disease | 2026-11-01 |
| NCT05558189Stanford UniversityVibrotactile Coordinated Reset for the Treatment of Post Surgery Refractory Parkinson's Disease Patients | 2026-11-21 |
| NCT06029686Stanford UniversityVibrotactile Coordinated Reset for Parkinson's Patients of a More Variable Population | 2026-12 |
| NCT06028477Stanford UniversityVibrotactile Coordinated Reset in Parkinson's Disease - Proof of Concept Study | 2026-12-30 |
| NCT06559098Stanford UniversityVibrotactile Coordinated Reset (vCR) for the Treatment of Advanced Parkinson's Disease Patients Who Have Previously Received vCR Stimulation | 2027-01 |
Among the 19 studies in Parkinson Disease by Stanford University, from their registry updates:
Parkinson's disease often causes constipation and changes in gut bacteria, but it is not known how quickly a daily fiber supplement changes gut physiology in people with Parkinson's, or how long any change lasts after stopping. This study will test how a daily fiber bar affects bowel function and gut inflammation in people with Parkinson's disease and in household members who live with them. Participants will eat one fiber bar (11 grams of fiber) each day for 3 months, then stop and be followed for one more month, for about 4 months in total. At three points (before starting, after 3 months of fiber, and one month after stopping), participants will collect a stool sample at home and mail it to Stanford in a provided kit, so no clinic visits are needed. Every week, participants will also fill out a short questionnaire about how often they have bowel movements, their bowel regimen, and they will complete a questionnaire about how bowel symptoms affect their daily life. In the lab, we will measure proteins in the stool that are signs of gut inflammation. We want to learn how fast these proteins change when fiber is added, whether changes last after fiber is stopped, and whether people with Parkinson's respond differently than their household partners. We expect that fiber will change gut inflammation and bowel function during the fiber period, and that these changes will differ between people with Parkinson's and their partners after the fiber bars are stopped. Results may help guide future research on diet and gut function in Parkinson's disease.
Rationale:
Parkinson's disease (PD) is a progressive neurological disorder, and the biological drivers of disease progression remain poorly defined. Gastrointestinal (GI) dysfunction is among the earliest and most common non-motor features of PD, and constipation, dysbiosis, and an altered gut microbial composition are reported in up to \~80% of people with PD (PWP). PWP show reduced abundance of commensal taxa that produce metabolites, notably short-chain fatty acids (SCFAs), that are involved in intestinal motility, epithelial barrier integrity, and mucosal immune homeostasis. SCFAs are generated by microbial fermentation of dietary fiber. SCFA supplementation has been associated with cognitive changes in animal models and in a small pilot cohort of PWP. Greater non-motor symptom burden, as measured by MDS-UPDRS Part I, is associated with increased risk of dementia in PD, which is one reason the gut is of interest in PD research.
In the general population, fiber supplementation is associated with increased stool frequency and bowel regularity, and it has been proposed as a way to support bowel function and the gut microbiome in PWP. Response to fiber depends on baseline microbiome composition and function, but the responsiveness (flexibility) of the PD microbiome to fiber has not been characterized, and the time course over which fiber changes bowel function or gut inflammation in PWP has not been systematically studied. This study addresses that gap.
Animal studies support a role for the gut microbiome in Parkinson's disease. In a genetically modified mouse model of Parkinson-like disease, germ-free mice showed fewer movement problems and less brain inflammation than mice with a normal microbiome, even though both groups had the same genetic risk. When germ-free mice received gut bacteria from people with Parkinson's disease, their symptoms worsened, whereas bacteria from healthy human donors did not worsen movement symptoms (Sampson et al., 2016). This suggests that gut bacteria may be involved in the disease process and not only accompany it.
Study design:
SUNs is a 4-month, open-label, two-arm interventional study with three longitudinal timepoints: baseline (no supplementation), the end of a 3-month fiber supplementation period, and one month after cessation. PWP are enrolled together with a cohabitating control (household partner), and both receive the same intervention. Dyad-based enrollment is intended to reduce environmental and dietary confounding of the gut microbiome. Participants are recruited from an existing Stanford biobank of 79 PWP/cohabitating control dyads, so baseline characterization already exists for the candidate pool.
The intervention is a prebiotic fiber bar containing 11 g of fiber, manufactured by Sorridi Therapeutics, at a dose of one bar per day as recommended by the study dietitian. Participants may choose one flavor (Lemon Cranberry or Dark Chocolate Cherry) or receive an equal shipment of both. Tolerability was previously assessed in an open-label, single-arm pilot (NCT07127120); in a sponsor-reported summary, 18 adults with Parkinson's disease ate one bar daily for 28 days, all completed the study, and no serious adverse events were reported. SUNs extends daily exposure to 90 days. The NeuroFiber bars are donated by Sorridi Therapeutics.
Specific aims and hypotheses:
Aim 1: Determine whether fiber supplementation changes fecal inflammatory protein levels over time in PWP. We hypothesize that Neurofiber supplementation will change fecal inflammatory protein levels (e.g., TNF-α, IL-6, CRP), and that the persistence of these changes after cessation will differ between controls and PWP.
Aim 2: Determine the rate at which initiation and cessation of fiber supplementation affects bowel function in PWP. We hypothesize that bowel function (Bristol Stool Form Scale, defecation frequency, and bowel symptoms) will change in both PWP and controls during supplementation, and that these measures will return toward baseline at different rates in PWP and controls after cessation. Bowel symptoms and bowel-related quality of life (PAC-SYM and PAC-QoL) are assessed longitudinally in parallel.
Biospecimen collection and processing:
Stool is collected remotely by participants using commercial stool collection kits (DNA Genotek, Zymo, and OMNImet Gut collection tubes) and returned by mail to Stanford, where samples are preserved for downstream protein isolation and quantification. Collecting at home enables the repeated longitudinal sampling this design requires and supports retention. We will also preserve these samples for downstream metagenomic and metabolomic analysis.
Protein quantification:
Fecal proteins will be isolated and quantified in collaboration with the Stanford Human Immune Monitoring Center (HIMC). Inflammatory protein levels will be measured using the NULISA (NUcleic acid Linked Immuno-Sandwich Assay) platform, a proximity-ligation immunoassay with DNA-barcoded antibodies and sequencing or qPCR readout that allows highly sensitive, multiplexed protein detection from very small sample volumes.
Analysis:
Longitudinal changes in fecal inflammatory proteins and in questionnaire-based bowel measures will be compared across the three timepoints within participants and between PWP and cohabitating controls.
Significance and future directions:
The study will define the extent and time course of PD gut microbiome adaptation to fiber and test whether adaptation is associated with changes in bowel function and gut inflammation. These data are intended to inform future research on diet, the gut microbiome, and the gut-brain axis.
Inclusion Criteria Arm 1:
Inclusion Criteria Arm 2:
Exclusion Criteria Arm 1:
Exclusion Criteria Arm 2:
Participants with a clinical diagnosis of Parkinson's disease who live with a participating household partner. Participants eat one NeuroFiber bar (11g fiber) daily for 3 months, then stop for a 1-month washout. Stool samples are collected at baseline, after 3 months of supplementation, and 1 month after stopping. Bowel function is tracked with weekly questionnaires throughout the 4-month study. This arm is the primary population for testing how quickly fecal inflammatory proteins and self-reported bowel function change with fiber initiation and cessation.
Drug: Prebiotic fiber bar
Participants who live with a participating household partner that has been diagnosed with Parkinson's disease. Participants eat one NeuroFiber bar (11g fiber) daily for 3 months, then stop for a 1-month washout. Stool samples are collected at baseline, after 3 months of supplementation, and 1 month after stopping. Bowel function is tracked with weekly questionnaires throughout the 4-month study. This arm is the control population for testing how quickly fecal inflammatory proteins and self-reported bowel function change with fiber initiation and cessation.
Drug: Prebiotic fiber bar
NeuroFiber® prebiotic fiber bar (Sorridi Therapeutics): a vegan, plant-based whole-food bar with a proprietary blend of 14 prebiotic and whole-food fibers, formulated as a source of prebiotic fiber to support short-chain fatty acid-producing gut bacteria. Each bar is one serving (50 g) with 11 g of fiber. Participants eat one bar daily and may choose one flavor (Lemon Cranberry or Dark Chocolate Cherry) or receive an equal shipment of both. Ingredients include a prebiotic fiber blend, date paste, almonds, walnuts, whole-grain oats, pumpkin and chia seeds, fruit, coconut, green tea extract, and vitamins D3, B12, and E; Lemon Cranberry also contains cashews and flax seeds, and Dark Chocolate Cherry also contains cocoa products. No inulin or gums. Contains tree nuts. Donated by the manufacturer. Tolerability previously assessed in open-label pilot NCT07127120.
Also known as: Neurofiber bar
Fecal Inflammatory Protein Quantification
Fecal inflammatory proteins will be quantified with a multiplex immunoassay of 250 cytokines, chemokines, and other inflammation-related proteins. The primary analyses are the 1) protein level change from baseline to Month 3, 2) protein level change after a one month wash out at month 4 in a pre-specified set of key proteins (eg., TNF and IL-6). Levels will be compared between people with Parkinson's disease and cohabitating controls.
Time frame: Baseline (Day 0), end of fiber supplementation (Month 3 or 90 days, whichever is first), and end of 1-month washout (Month 4 or 120 days, whichever is first)
Bristol Stool Form Scale (BSFS) score
Participants will complete a weekly bowel regimen questionnaire that includes the Bristol Stool Form Scale (BSFS), a validated 7-point scale of stool consistency (types 1-2 indicate constipation, 3-5 normal stool, and 6-7 diarrhea). Participants take one 11 g prebiotic fiber bar daily for 3 months, followed by a 1-month washout. The primary analysis is the rate of change in weekly BSFS score after starting supplementation (Weeks 1-12) and after stopping it (Weeks 13-17). Changes are compared between people with Parkinson's disease and cohabitating controls. Defecation frequency and other bowel symptoms from the same questionnaire are reported as separate secondary outcomes. Increase in BSFS score = decrease in constipation symptom report.
Time frame: Weekly from baseline through Month 4 (Weeks 1-17).
Change in weekly defecation frequency during fiber supplementation and washout
Self-reported number of bowel movements per week from the weekly bowel regimen questionnaire. Rate of change is evaluated during supplementation and during the 1-month washout and compared between people with Parkinson's disease and cohabitating controls.
Time frame: Weekly from baseline through Month 4 (Weeks 1-17); supplementation phase ends at Day 90 or 3 months, whichever is first.
Change in Patient Assessment of Constipation Symptoms (PAC-SYM) score across fiber supplementation and washout
The PAC-SYM is a validated 12-item self-report questionnaire with abdominal, rectal, and stool symptom subsections. Total scores are collected at baseline and weekly through Month 4 (Weeks 1-17). Changes from baseline to end of supplementation and from end of supplementation to end of washout are compared between people with Parkinson's disease and cohabitating controls. Higher total score indicates worse symptoms. A negative change from baseline = less constipation-related burden, positive change = more constipation-related burden.
Time frame: Weekly from baseline through Month 4 (Weeks 1-17); supplementation phase ends at Day 90 or 3 months, whichever is first.
Change in Patient Assessment of Constipation Quality of Life (PAC-QoL) score
AC-QoL total scores will be assessed at baseline and weekly through Month 4 (Weeks 1-17). A negative change from baseline = less constipation-related burden, positive change = more constipation-related burden.
Time frame: Weekly from baseline through Month 4 (Weeks 1-17); supplementation phase ends at Day 90 or 3 months, whichever is first.
Change in gut microbiome composition and function across fiber supplementation and washout
DNA extracted from stool will undergo shotgun metagenomic sequencing. Gut microbe composition (ie., total abundance) will be assessed. Changes from baseline to end of supplementation and from end of supplementation to end of the 1-month washout are compared between people with Parkinson's disease and cohabitating controls. Increase in complexity (different types of gut microbiota) = generally healthier outcome.
Time frame: Baseline (Day 0), end of fiber supplementation (Day 90 or 3 months, whichever is first), and end of 1-month washout (Day 120 or 4 months, whichever comes first).
Change in fecal metabolite profile (metabolomics) across fiber supplementation and washout
Stool metabolites will be profiled using mass spectrometry, including microbial metabolites such as short chain fatty acids. Changes in individual metabolite abundance and pathway-level profiles from baseline to end of supplementation and from end of supplementation to end of the 1-month washout are compared between people with Parkinson's disease and cohabitating controls. Multiple-comparison correction will be applied.
Time frame: Baseline (Day 0), end of fiber supplementation (Day 90 or 3 months, whichever is first), and end of 1-month washout (Day 120 or 4 months, whichever comes first).
Change in autonomic symptoms (SCOPA-AUT total and gastrointestinal subscale score) across fiber supplementation and washout
The SCOPA-AUT is a validated self-report questionnaire of autonomic symptoms over the past month, with gastrointestinal, urinary, cardiovascular, thermoregulatory, pupillomotor, and sexual domains. Each item is scored 0 (never) to 3 (often). Total score (0-69) and gastrointestinal subscale score (0-21) are collected at baseline, at the end of supplementation, and at the end of the 1-month washout. Changes from baseline to end of supplementation and from end of supplementation to end of washout only by participants with Parkinson's disease. Higher scores indicate worse autonomic symptoms. A negative change from baseline = less burden, positive change = more burden.
Time frame: Baseline (Day 0), end of fiber supplementation (Day 90 or 3 months, whichever is first), and end of 1-month washout (Month 4)
Change in participant-reported non-motor experiences of daily living (MDS-UPDRS Part IB) in people with Parkinson's disease across fiber supplementation and washout
MDS-UPDRS Part IB is a validated 7-item questionnaire covering non-motor symptoms over the past week, including constipation, urinary problems, lightheadedness on standing, fatigue, sleep problems, daytime sleepiness, and pain. Each item is scored 0 (normal) to 4 (severe), for a total of 0-28. Completed only by participants with Parkinson's disease. Total score and the constipation item are compared within participants from baseline to the end of supplementation and from the end of supplementation to the end of the 1-month washout. Higher scores indicate worse symptoms. Higher score = increased burden.
Time frame: Baseline (Day 0), end of fiber supplementation (Day 90 or 3 months, whichever is first), and end of 1-month washout (Month 4).
Change in participant-reported motor experiences of daily living (MDS-UPDRS Part II) in people with Parkinson's disease across fiber supplementation and washout
MDS-UPDRS Part II is a validated 13-item participant questionnaire on the impact of motor symptoms on daily activities over the past week (for example speech, eating, dressing, hygiene, walking, tremor). Each item is scored 0 (normal) to 4 (severe), for a total of 0-52. Completed only by participants with Parkinson's disease. Total scores are compared within participants from baseline to the end of supplementation and from the end of supplementation to the end of the 1-month washout. Higher scores indicate greater motor disability. A negative change from baseline = less burden, positive change = more burden.
Time frame: Baseline (Day 0), end of fiber supplementation (Day 90 or 3 months, whichever is first), and end of 1-month washout (Month 4).
Association of baseline Parkinson's disease risk factors (PD-RFQ) with fecal inflammatory protein, microbiome, and metabolite response to fiber supplementation
Participants will complete the Parkinson's Disease Risk Factor Questionnaire (PD-RFQ) at baseline to capture environmental, lifestyle, and medication exposures. At Month 4, participants will confirm whether their residential address or employment has changed since baseline, to verify that exposures were stable during the study. Exploratory analyses will test whether baseline risk factors are associated with changes in fecal inflammatory proteins, gut microbiome composition, and fecal metabolites from baseline to the end of supplementation and through the 1-month washout. Participants with a change in address or employment will be flagged and examined in sensitivity analyses. Higher score = higher estimated PD risk.
Time frame: Baseline (Day 0) for PD-RFQ; Month 4 for confirmation of address and employment
Plan to share: Yes — De-identified individual participant data may be shared with qualified researchers upon reasonable request, subject to participant privacy protections, institutional policies, and applicable data use agreements. Specific data elements available for sharing will be determined at the time of the request. Raw metagenomic sequence data will not be shared due to containing human DNA sequences that could pose a risk to participant privacy.
Supporting information: Study protocol
Time frame: Data and supporting information may become available following publication of the primary results, and will remain available for a reasonable period determined by the study team and Stanford University institutional policies.
Access criteria: Qualified researchers may request access by contacting the study team. Requests will be reviewed by the study team and may require a data use agreement, institutional approval, and a brief description of the intended use. Data will be de-identified and provided through a secure transfer method. Raw metagenomic sequence data will not be shared.
Start is estimated for Dec 2026; primary completion for Jul 2027, 7 months later.
Of 77 non-industry phase 1 interventional studies under Parkinson Disease, half reached primary completion within 37 months of starting (the median), counting those still running; a quarter within 20 and three quarters within 68. This study's planned 7 months is below that.
Counting every sponsor, half of 204 studies reached it within 19 months; a quarter within 5 and three quarters within 40.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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