Much is poorly understood about the gut/brain connection.
A study in Finland found that PD patients have a very different makeup of gut bacteria. Here's a link ..
http://www.alphagalileo.org/ViewItem...CultureCode=en
In short, entero bacteria is toxic and PD patients have tons of it, whereas the normal person does not. Also PD patients are very light on lacto bacteria, which produces lactic acid to control toxins in the gut.
I previously wrote about this issue here, including way to get your gut bacteria tested cheap .. I have not done it yet (still digesting my 23andme results!)
http://neurotalk.psychcentral.com/thread221379.html
Also, after reading up on gut bacteria I have found that parmigiano reggiano cheese (aged at least 24 months) has massive amounts of a lacto bacteria that suppresses the entero bacteria. I've been doing this cheese for about 2 weeks and my metabolism has changed a bit. I eat the cheese (very tasty BTW) before bed and in the AM I feel the urge when I get up. It must be doing something. BTW, I do NOT have constipation as a PD symptom. This is NOT Parmesan Cheese, which is a faked up version of the original and made in a number of different ways.
Anyways, I'm just writing this out of my head so I may not have the exact names of the bacteria correct .. there are tons of different strains but there you go. We are getting more and more data pointing to the gut as the source of at least one kind of PD anyway. Fight it on all fronts!