I'll edit this as I learn more.
I've been researching how to delay/slow Parkinson's with diet/nutrition. These are proven by many epidemiological studies and/or in animals, but my list is restricted to compounds that are also known to cross the blood-brain barrier in humans. I now have a twitch in my left thumb and index finger if I put them in the right position. Here's the ideal diet:
1 to 3 packs of cigarettes worth of nicotine per day
3+ cups of green tea (2+ pills of the extract)
raw broccoli twice a day
3+ cups of black tea (2+ pills of the extract)
2 beers w/ 3 tablespoons brewer's yeast or can of sardines to raise uric acid to gout-danger levels
coconut oil to provide brain energy by ketones since the glucose energy path has been compromised
3 egg yolks or equivalent shrimp to raise cholesterol in diet. Low cholesterol causes damage.
1200 IU vitamin E
2000 IU vitamin D
fish oil (heavy on omega-3's)nn
3+ cups of coffee (or caffeine pills)
No milk products
selenocysteine (need to investigate)
Many of these are (not by coincidence) free-iron chelators in the brain (nicotine, caffeine, tea extracts, uric acid, and possibly omega-3s), regardless of whatever other benefit they provide.
Ideally, the beer and yeast are split to 2 or 3 times a day with lactic-acid generating exercise which blocks uric acid excretion. Exercise also lessons danger to neurons that are in the process of trying to die by increasing oxygen levels in the brain.
Also, limit intellectual activities and try to work outside. (high school educated outdoor workers get it at least 10 years later than others). Also, sleep as good as possible and no mind/emotion stressors.
There is a laundry-list of things that placed me in the higher-risk category (male, intellectual, 1970's pesticide exposure in youth (4x to 10x risk increase), non-smoker (4x risk), severe elemental mercury vapor exposure at age 11, milk, history of very low vitamin D) but for several reason's my high-dose vitamin C "exposure" (10 grams/day for for 10 years) increasing free-copper (if not free-iron) is my best guess.