Chocolate consumption has long been associated with enjoyment and pleasure. Popular claims confer on chocolate the properties of being a stimulant, relaxant, euphoriant and antidepressant. These possible pharmacological actions might be related to various biogenic amines, such as serotonin, dopamine, tyramine, histamine, phenylethylamine and cannabinoid-like substances. Most amines are metabolized by monoamineoxidase-A (MAO-A) and are therefore unable to pass the blood-brain-barrier. In contrast, phenylethylamine is a direct dopamine releasing ingredient and as a substrate of MAO-B and due to its lipophilic structure even capable to pass the blood-brain-barrier. Within this line, own clinical observations suggested an increased chocolate consumption in patients with Parkinson's disease (PD) compared to healthy subjects and to their pre-disease state.

In a previous study, we assessed the consumption of chocolate and non-chocolate sweets in PD patients and their partners (as household controls) using a self-questionnaire. Consumption of chocolate was significantly higher in PD patients compared to controls, while consumption of non-chocolate sweets was similar in both groups. Our study suggests that chocolate consumption is increased in PD independent of concomitant depressive symptoms measured by BDI-1. Although reasons for increased chocolate consumption in PD remain elusive, it may hypothetically be a consequence of the high content of various biogenic amines as a content of cocoa influencing dopamine metabolism.

Therefore, in the present study we aim to study the effects of dark chocolate with high cocoa content (85%) compared to chocolate without any cocoa (white chocolate) on motor symptoms in PD patients as measured with UPDRS part III (motor score). The principle design of the intervention is similar to the standard pharmacological challenge test for studying effects on motor symptoms in PD (e.g. levodopa challenge test).

Inclusion Criteria:

• Age of 18 Years or older
• Idiopathic Parkinson's disease, according to UKBB criteria
• Hoehn & Yahr Score II-III
• 16 Points or more in UPDRS part III scale
• Sufficient ability to follow the study procedure for at least 3 hours
• Ability to give informed consent
• Stable antiparkinsonian medication for at least 4 weeks prior to study inclusion

Exclusion Criteria:

• Psychiatric conditions, severe enough to interfere with study procedures
• motor or affective fluctuations or dyskinesias
• treatment with COMT and/or MAO inhibitors
• Diabetes mellitus