Nutrition are importance for those with Parkinson Disease. Nutrition won't cure PD or slow its progression.
There are vitamins and mineral at certain level are harmful for Parkinson's Patients especially Folic Acid, Chromium,Copper, Ferritin,Magnessium,Selerium,Zinc and vitamin B6.
Therefore doctor who prescribes vitamins for PD has to routinely monitor them. Some of them may be good for general health and well being but not have been definitively proven to help PD. CoQ10 and creatine are currently under study. We will know about these two drugs very soon. But for the rest, they have not been proven.
In short Dietian with parkinson's experience are helpful