Hi Krugen68
Very interesting indeed! I had seen a reference to the Helicobacter P. study but your text below is a lot more clear an instructive than what I saw - thanks.
In terms of relationship between gastro and Parkinson, I also found a very interesting french study from 2010. In essence they were able to diagnose PD (and to some extent the level of advance of the PD symptoms) just by looking at someone's intestines (doing a colon biopsy). The title of the paper is "Colonic Biopsies to Assess the Neuropathology of Parkinson’s Disease and Its Relationship with Symptoms" http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0012728 This paper does not make any statements regarding which side causes the other but it does establish a pretty convincing link between PD and the gastro system (and in particular the intestines).
I'm not sure yet what to make of this idea that Helicobacter P. may produces a neurotoxic compound that might kill off nerve cells... but am clearly interested in it (if anyone has more info on this I would appreciate). In the meantime I'm not yet discarding the other possible explanation that high or low gastric acidity levels (and it seems to be established that Helicobacter P. causes low gastric acid... though I guess the cause could possibly be something else too like ulcers, etc) may create absorption problems leading to deficiences in the key ingredients one needs as per my original post above. I should get my test results for the different Vit B levels in the next few days. If they don't come normal I'm going to ask my gastro-entorolgist to test stomach acidity levels to see if there's something in there. If there's nothing, at least that's one hypothesis I can close down and focus on the others.
Cheers,
lfs