The goal of this pilot study is to examine the feasibility and effects of an 18-month intervention diet compared to an active control diet (standard diet) in those living with Parkinson's Disease (PD), without dementia.

Research has shown that eating components of Mediterranean diets are associated with a 30% lower risk to develop PD and a 40% lower mortality rate in those living with PD. Diet may influence the gut and microbiomes, thus may affect PD risk and progression.

This study will examine how easy it will be to adhere to a certain type of diet for 18 months and what changes may occur in the gut microbiome and in PD symptoms on a specific diet during that time.

The study will involve in-person study visits at UBC as well as online diet coaching sessions and online group cooking classes over Zoom.

This is a randomized study, meaning that participants will be assigned by chance to either the Mediterranean-style diet group or the standard diet group for the duration of the 18 months.

This pilot study will also examine recruitment rates and retention, in order to prepare for a larger future study.

Those meeting general eligibility criteria and are agreeable, will come to the University of British Columbia (UBC) for an onsite Screening visit to sign the consent form, review eligibility, and complete assessments. If the additional study criteria is met during the Screening and the 4-week run-in phase, an onsite Baseline assessment will occur over 2 days. At Baseline, each participant will be randomized to either (1) the "yellow cooking group", or (2) the "blue cooking group". Participants will remain in their assigned groups for the duration of the study. Participants will also be provided with a wearable wrist device to record daily physical movement and lifestyle factors during the 18 months.

Participants in both groups will receive virtual/remote coaching (nutrition training) and group cooking classes, and also complete questionnaires (at home and in-person) and collect biological samples (urine, faecal). Onsite (in-person) visits will occur at Screening, Baseline, 3 months, 6 months, 12 months, and 18 months (end); these will include questionnaires, blood sample collections, participant feedback, magnetic resonance imaging (MRI) scans (Baseline and 18 months only).

Inclusion Criteria:

Eligible if the person living with Parkinson's has/is:

1. a clinical diagnosis of PD,
2. cognitively stable (no clinical dementia),
3. between 40-80 years old,
4. able to travel to UBC for 6 onsite visits over 18 months,
5. sufficient English proficiency (coaching and cooking classes are in English only),
6. on a stable dopaminergic medication for at least one month before baseline,
7. computer and internet access at home, and can be available via video link for at least 80% of the study sessions.

Exclusion Criteria:

Not eligible, if person has/is:

1. a diagnosis of atypical parkinsonism,
2. medical or psychiatric conditions that would prevent full participation in the nutrition intervention (such as food allergies), significant dysphagia, diabetes on insulin, anti-coagulation on warfarin, and inflammatory bowel disease,
3. clinical dementia,
4. unable to complete questionnaires or understand study instructions,
5. using of immunomodulatory agents,
6. used Probiotics in the last 4 weeks prior to study start,
7. used Antibiotics in the last 3 months prior to study start,
8. contraindications for MRI.

Diet groups will be labelled without reference to the specific diet allocation (example: "Yellow cooking group" or "Blue cooking group") for all participant communication.

Random assignment to either:

1. the active intervention diet group, or
2. the standard-of-care diet.