What Causes Parkinson Disease?

Hello Dr. Weil, My husband has Parkinson s disease which started 6 years ago, now but doing quite well, he only has a slight twitch in his lip and sometimes a weakness in his feet and his memory is not as sharp as it used to be. He also has prostate cancer, but in great remission for the last 3 years. Dr. told him he may be a borderline diabetic, he does not take any prescription for it, he just takes good care of his diet. Can he take your Juvenon pills, would they help him, especially with his memory? Thank you,