This study evaluates plasma concentrations of pharmacologically active constituents of chocolate and their effects on motor and non-motor symptoms of Parkinson's disease. Following one week of abstinence from cocoa-containing products, patients with Parkinson's disease will be randomized to receive either dark or white chocolate. After one week of chocolate consumption, patients will then cross over to white or dark chocolate, respectively, and take the corresponding chocolate product for another week. Blood samples will be taken at baseline, week 1 and week 2 to examine plasma concentrations of pharmacologically active constituents of chocolate at all three timepoints. Moreover, patients will be clinically examined for motor and non-motor symptoms at all visits.

Inclusion Criteria:

• Female or male individuals aged 40 years and above
• Parkinson's Disease according to the UK Parkinson's Disease Society Brain Bank Clinical Diagnostic Criteria
• Hoehn and Yahr stage I-III
• Minimum score of 16 points in the motor part of the Unified Parkinson Disease Rating Scale (UPDRS part III)
• Stable antiparkinsonian medication for at least 4 weeks prior to study inclusion
• Ability to provide informed consent

Exclusion Criteria:

• Clinical signs for a secondary or atypical Parkinsonian syndrome
• Treatment with any investigational medical product within 30 days prior to study inclusion
• Intake of chocolate or other cocoa-containing products within the last 7 days prior to study inclusion (patients can be re-screened after 7 days of abstinence from chocolate and other cocoa-containing products)
• Known intolerance or allergies against chocolate or other cocoa-containing products
• Diabetes mellitus and/or impaired glucose tolerance in the medical history
• Alcohol or drug abuse in the medical history
• Presence of levodopa-induced motor complications
• Other neurological, psychiatric or miscellaneous conditions that would significantly impair study participation, medical assessments or the consenting process