In this prospective, intervention study, participants with diagnosed Parkinson's disease will be instructed to follow a Mediterranean diet for five weeks. Gut permeability will be assessed using food-grade sugar molecules. Participants will provide urine and stool samples to assess gut permeability and microbial communities.

Inclusion Criteria:

• Physician-diagnosed Parkinson's disease aged 21-85 years
• Hoehn & Yahr stage <3
• Currently living in the same household with a healthy spouse/partner who meets study eligibility criteria and is willing to participate
• Willing and able to complete informed consent in English
• Willing to complete daily and weekly questionnaires and 6 dietary recalls over approximately 7 weeks
• Willing to avoid beer, wine, and cocktails on the day before and the day of the sugar probe tests.
• Willing to provide urine and stool samples during the study collection periods.
• Willing and able to fast (no food or drink, except water or tea) for a prolonged period of time during study urine collections.
• Willing to maintain usual diet through the pre-baseline period
• Willing to make dietary changes to follow a Mediterranean dietary pattern during the intervention period.
• Willing to discontinue taking prebiotic, fiber, probiotic, herbal, or high-dose vitamin or mineral supplements that may impact inflammation during the pre-baseline period and throughout the study protocol.
• Willing to limit use of oral laxative medication to an "as-needed basis" (i.e. <3 times per week) during the full length of the study
• Willing to avoid high intensity exercises two days prior to and the day of the permeability tests. These tests will be done on two occasions.
• Willing to provide a social security number to receive study payment.

Exclusion Criteria:

• Does not meet above criteria
• Atypical or secondary Parkinsonism
• History of deep brain stimulation
• Daily use of NSAIDs in the last 3 months or incidental use in the last 2 weeks prior to screening.
• Daily use of anticholinergics or prokinetic agents
• Use of enemas or suppositories to alleviate constipation
• Use of another investigational product within 3 months of the screening visit.
• Antibiotic use within 2 months from the day of stool collection
• Good adherence to the Mediterranean diet during the pre-baseline period (score >6) based on the 14-item Mediterranean Diet Assessment Tool
• Physician-diagnosed gastrointestinal disease or condition (such as ulcerative colitis, Crohn's disease, gastroparesis, cancer, peptic ulcer disease, Celiac disease, short bowel disease, ileostomy, colostomy) other than gastroesophageal reflux or diverticular disease