I just received an email that was forwarded to my dad about a Fava-bean-based nutraceutical study, and checked here but no one has mentioned it. It only linked to one study, which was funded by the company who manufactures the supplement, but the study has a sample size of 119 people and claims to increase dopamine levels in the blood by a significant amount. I am reluctant to get excited about this, but perhaps others have info:

Finally: Parkinson disease: Spanish research team found two major keys of the neuroprotection and natural increase of dopamine – Live Better Parkinson's