Grant: Doctoral Research Award: Canada Graduate Scholarships

There is growing interest in the use of dietary interventions to manage bothersome symptoms in Parkinson's disease (PD). However, consensus has yet to be reached on the optimal diet for persons living with PD (PwP). Gastrointestinal symptoms and cognitive changes are two symptom domains which PwP have identified as particularly impactful on quality of life. Several studies have shown that adherence to a high-fibre Mediterranean diet (MeDi) may help to relieve gastrointestinal symptoms in PwP by promoting healthy changes in the composition of microorganisms living in the gut - termed the "gut microbiome." Concurrently, emerging evidence has suggested cognitive benefits from adherence to high-fat, low-carbohydrate or "ketogenic" diets (KDs) in PD. However, preliminary studies have raised concerns regarding the use of KDs in PwP, due to potential adverse effects on the gut microbiome. Combining MeDi and KD nutritional principles may thus represent a means to safely address PD-related gastrointestinal and cognitive symptoms in tandem. To test this hypothesis, we are running a clinical trial investigating the effects of two combined MeDi-KD interventions on PD symptoms and gut microbiome composition in 50 participants with PD. Participants will be randomized to follow one of the two dietary regimens first for 8 weeks, after which changes in symptoms and indicators of gut health will be assessed relative to baseline. Participants will then follow their normal diet for 8 weeks before repeating the study protocol with the second dietary intervention. Safety, feasibility and exploratory clinical efficacy outcomes of this trial will help to determine whether these diets can be safely studied in a larger-scale, longer-duration clinical trial in PwP. Ultimately, the results of this pilot trial and any subsequent larger studies may inform the development of new dietary guidelines for PwP.