Here's some pretty recent study results, specific to gut link to PD.

I'm a newbie so I have to*edit*

The most interesting thing in this study is that it names the bacteria that are out of whack ..
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I myself am taking caprylic acid supplements (found in coconut oil BTW) to reduce some of the candida bacteria I have. Apparently one sign that bacteria overgrowth has expanded into the small intestine is excessive gas and a pungent smell when defecating. I'm guilty on both counts.

Next month I have a colonoscopy, which wipes out most of the flora, and then I'll be taking a few different probiotics. I am gonna see if it changes things for me.