Objective: To assess the relationship between diet in the relationship between non-motor symptoms in Parkinson’s disease (PD).

Background: While the etiology of PD is not fully understood, the hypothesis of two distinct phenotypes determined by the origin of pathology (“brain-first” and “body-first”) has been gaining greater awareness [1,2]. In brief, people with PD (PwP) with body-first pathology present more frequently with non-motor symptoms, like constipation and hyposmia, than those with brain-first pathology [3]. However, further investigation into whether the synchrony of these non-motor symptoms is due to alpha-synuclein burden or a mediating variable such as diet, noted to be altered in hyposmia, is required [4,5].

Method: 173 PwP (disease duration <14 years, age: 40-85 years) were enrolled into a multi-year longitudinal observational study of the microbiome across 5 annual study visits [6]. Motor and non-motor symptoms were evaluated using the MDS-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS). Olfaction was evaluated using the Sniffin’ Sticks Test (Burghardt®, Germany) while constipation and diet were assessed via the Constipation Severity Scale (CSS) through the Rome III Criteria Module and a Food Frequency Questionnaire (FFQ), respectively.

Results: At baseline, all participants completed the FFQ, Rome III, and MDS-UPDRS assessments in the ON state while 172 participants completed the Sniffin’ Sticks Test. Completion rates at each timepoint are summarized in [Table 1]. Sniffin’ Stick total and Hoehn-Yahr stage significantly predicted CSS in PwP (𝛽 = -0.333±0.123, p =.007**; 𝛽 = -1.237±0.537, p= .02*, respectively, multiple regression) at baseline [Table 2]. Upcoming analyses will investigate the longitudinal relationship between diet, constipation, and olfaction in PwP using mediation analysis.

Conclusion: This study will determine whether poor diet (e.g. higher processed carbohydrates, lower fibre) plays a mediating role in the relationship between hyposmia and the progression of constipation in PwP.  These findings will provide insight into the body-first phenotype and future directions for PD lifestyle interventions and prodromal (e.g. REM sleep behavior disorder) research.

Table 1. Completed visits at all timepoints

Table 2. Multiple regression of CSS in PwP

References: 1. Borghammer P, Van Den Berge N. Brain-First versus Gut-First Parkinson’s Disease: A Hypothesis. J Parkinsons Dis. 2019;9(s2):S281-S295. doi: 10.3233/JPD-191721. PMID: 31498132; PMCID: PMC6839496.

2. Nuzum ND, Loughman A, Szymlek-Gay EA, Teo WP, Hendy AM, Macpherson H. To the Gut Microbiome and Beyond: The Brain-First or Body-First Hypothesis in Parkinson’s Disease. Front Microbiol. 2022 Mar 30;13:791213. doi: 10.3389/fmicb.2022.791213. PMID: 35432226; PMCID: PMC9005966.

3. Horsager J, Borghammer P. Brain-first vs. body-first Parkinson’s disease: An update on recent evidence. Parkinsonism Relat Disord. 2024 May;122:106101. doi: 10.1016/j.parkreldis.2024.106101. Epub 2024 Mar 15. PMID: 38519273.

4. Alia S, Andrenelli E, Di Paolo A, Membrino V, Mazzanti L, Capecci M, Vignini A, Fabri M, Ceravolo MG. Chemosensory Impairments and Their Impact on Nutrition in Parkinson’s Disease: A Narrative Literature Review. Nutrients. 2025 Feb 13;17(4):671. doi: 10.3390/nu17040671. PMID: 40004999; PMCID: PMC11858080.

5. Ådén E, Carlsson M, Poortvliet E, Stenlund H, Linder J, Edström M, Forsgren L, Håglin L. Dietary intake and olfactory function in patients with newly diagnosed Parkinson’s disease: a case-control study. Nutr Neurosci. 2011 Jan;14(1):25-31. doi: 10.1179/174313211X12966635733312. PMID: 21535918.

6. Metcalfe-Roach A, Cirstea MS, Yu AC, Ramay HR, Coker O, Boroomand S, Kharazyan F, Martino D, Sycuro LK, Appel-Cresswell S, Finlay BB. Metagenomic Analysis Reveals Large-Scale Disruptions of the Gut Microbiome in Parkinson’s Disease. Mov Disord. 2024 Oct;39(10):1740-1751. doi: 10.1002/mds.29959. Epub 2024 Aug 28. PMID: 39192744.

« Back to 2025 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/the-role-of-diet-in-the-relationship-between-hyposmia-and-constipation-in-patients-with-parkinsons-disease/