Here's a single-case study involving Fisetin (found in strawberries, apples, and onions) that improved symptoms:
ncbi.nlm.nih.gov/pubmed/228...
"The basic diet alone failed to prevent decline due to PD. In 2009, the basic diet was enhanced with a good dietary source of both fisetin and hexacosanol. Six months after the patient started the enhanced diet rich in fisetin and hexacosanol, a clinically significant improvement in symptoms was noted; the patient's attending neurologist reported that the clinical presentation of cogwheel rigidity, micrographia, bradykinesia, dystonia, constricted arm swing with gait, hypomimia, and retropulsion appeared to be resolved. "
Someone posted details not in the abstract:
" The patient’s medication dosage in December 2008, before
beginning the complete diet rich in fisetin and hexacosanol,
included 7½ carbidopa/levodopa 25/100 and 1mg
of rasagiline daily. By June 2009, 6 months after starting the
complete diet rich in fisetin and hexacosanol, the patient was
able to reduce the medication dose to 4½ carbidopa/levodopa
25/100 and ½ mg of rasagiline daily, while benefiting
from amelioration of motor symptoms. In October 2011
medication doses were 6 carbidopa/levodopa 25/100 CR and
¼mg of rasagiline, while maintaining the significant improvement
in allCUSS motor movements obtained in 2009.
Then I found where the patient herself posted an update this year:
" I'm the retired dietitian in the article. (My neighbors wanted me to share how my walking, etc, improved so dramatically, thus the published article.) Here's an update. I was doing well until late 2013 when I developed an allergy (characterized by flushing and breathlessness) to strawberries and several other foods. By February 2014 I had to stop consuming strawberries. Many of my symptoms began to worsen. In June 2014 I started taking the Swanson brand of fisetin. To approximate the amount in strawberries I divide the each capsule into six portions, taking one at breakfast and one a dinner. Over several months my symptoms again improved.
" In January 2015 I became intolerant of rasagiline and synthroid, stopping both in February 2015. Without the rasagiline, I have more tremor, etc, but am able to function well. I'm currently taking 6 carbidopa/levodopa 25/100, and one 25/100 CR at 10 PM.
The one thing you have to be cautious about with a single study is according to one research analyst it seems that all PD patients are over prescribed and most will see little change with possibly some improvement with an appropriate cut in medication.
Nevertheless, anything that sounds safe and has possibilities I say "go for it." I just suggest reading up on the proper dosage and any side-effects first.