Improving the Antioxidant System
Of all the nutritional strategies available for Parkinson’s disease, antioxidants appear to be the most promising choices to prevent or slow the progression of this condition. Individuals whose diets include plenty of healthy foods containing antioxidants are less likely to develop Parkinson’s disease. Patients should consume foods, such as fruits and vegetables, that contain glutathione or can help produce it. Cyanohydroxybutene, a chemical found in broccoli, cauliflower, Brussels sprouts and cabbage, is also thought to increase glutathione levels. High intake of dairy products may lead to a higher incidence of Parkinson's disease.
        The following antioxidants may be helpful in addition to standard pharmaceutical therapy.

R-Alpha Lipoic Acid, 10 to 50 mg a day in the morning with breakfast. R-Lipoic acid is a powerful antioxidant and helps generate glutathione. See study in the research update section below.
CoQ10 -- this nutrient helps preserve dopaminergic neurons from toxins (see study below). A dose of 30 mg to 100 mg each morning with breakfast is reasonable. This nutrient also improves energy production in cells.
Natural Vitamin E complex, between 100 and 400 units a few times a week, preferably of mixed tocopherols, taken with any meal.
Natural Vitamin C with bioflavonoids between 100 and 300 mg twice a day. In addition to being an antioxidant, vitamin C also helps the production of L-dopa from tyrosine.
N-Acetyl-cysteine is an antioxidant that can help regenerate glutathione. A dose of 100 to 250 mg of NAC can be taken most mornings before breakfast.

Selenium is an antioxidant that can help increase levels of glutathione. A dose of 50 to 100 micrograms a day can be taken with any meal. Selenium is also normally found in multimineral pills.

Melatonin is the sleep hormone with antioxidant abilities. A dose of 0.3 to 1 mg can be taken one or three hours before bed for those with insomnia. Tolerance can develop with regular use and since we don’t know the long-term effects of nightly use, it’s best to limit the frequency of use of melatonin to once or twice a week. In the 1980s, some individuals taking a synthetic drug called MPTP developed symptoms similar to Parkinson’s disease. It was determined that MPTP causes an oxidative destruction of substantia nigra neurons. Interestingly, a study with rats has determined that the administration of melatonin is able to almost completely prevent the neurotoxicity from MPP, a toxin very similar to MPTP. The rats on melatonin and MPP did not get symptoms of Parkinson’s disease  while the controls on MPP alone did.

Providing Dopamine Precursors
L-dopa, the immediate precursor to dopamine, is a nutrient available by prescription. L-dopa (often combined with carbidopa) is the most commonly used medicine to treat Parkinson’s disease. It is possible that the use of L-dopa for prolonged periods causes oxidation and toxicity to brain cells. If this turns out to be true, it would further justify the recommendations that antioxidants be added to standard Parkinson’s disease therapy. There is, as of yet, no clinical proof that taking antioxidant supplements help those with Parkinson’s disease live longer but all indications point to the possibility that the course of the disease can be slowed by providing adequate antioxidant support.
        Tyrosine is an amino acid that can be converted into L-dopa. But there is no reason to take tyrosine if L-dopa is available. Another way to increase dopamine levels is with the use of B vitamins, particularly NADH. Preliminary studies have shown some benefit with NADH in the therapy of PD. Although more research is needed, for the time being, it would seem reasonable to add NADH at a dose of 2.5 mg. NADH can be taken every other morning on an empty stomach. NADH may also help regenerate the antioxidant glutathione which could be beneficial. Be careful when you add NADH when you are already taking L-dopa or other medicines that treat Parkinson’s disease, since the effects could be cumulative. The long-term effectiveness of NADH in patients with Parkinson’s disease is currently not known. Taking between one to three times the RDA for the B vitamins seems to be a reasonable option.
        An herb to consider for Parkinson's disease is Mucuna Pruriens which has been successfully used in India for centuries. Whether the form available in the US is effective is not clear at this time. We also know little about the ideal dosage of mucuna to treat Parkinson's disease.

Blocking Dopamine Breakdown
Dopamine is broken down in the brain by an enzyme called monoamine oxidase (MAO). When the activity of MAO is inhibited, dopamine stays around longer and this benefits those with Parkinson’s disease. Several drugs are available that block the activity of MAO. Selegiline is the most effective and the one used most commonly. The prescribed dosage is 5 mg a day.
        No nutrients are currently known that prevent the breakdown of dopamine. However, a study conducted on rats at the College of Humanities and Sciences, Beijing Union University, in Beijing, China, indicates that the Chinese herbs codonopsis and astragalus can inhibit MAO type B and increase the activity of the antioxidant SOD. We don’t have any human trials to determine whether these two herbs would benefit patients with Parkinson’s disease. Although selegiline is a very helpful medicine, high doses may increase the risk of heart irregularities.

Additional Nutrients to Consider
Some of the following nutrients may not be directly involved in making more dopamine, but could well improve general cognitive abilities. Many patients who have Parkinson’s disease, especially the elderly, have age related cognitive decline.

Fish oils at 500 to 1,000 mg a day of EPA/DHA with meals. The role of fish oils in Parkinson’s disease is not known, but they can generally improve overall brain health.
Gingko biloba at 40 to 60 mg most days with breakfast or lunch. This herb has antioxidant properties and helps improve memory and alertness.
Replacing hormones in patients with Parkinson’s disease may be an additional option. Whether pregnenolone, DHEA, or other hormones are helpful in Parkinson’s disease is currently not known.

It’s quite likely that the proper use of natural supplements can reduce the necessary dose of L-dopa, selegiline, and other drugs currently used to treat Parkinson’s disease, or help slow down the progression of the condition. There’s still a great deal we need to learn about the nutritional treatment of Parkinson’s disease.

Common medicines used in Parkinson's disease
There are basically three types of drugs that are commonly prescribed for patients with Parkinson’s disease. First, doctors prescribe dopamine precursors, such as L-dopa, which converts into dopamine. A second approach is using drugs that block the breakdown of dopamine. A common medicine used for this purpose is selegiline (also known as deprenyl). And third, drugs are provided that influence dopamine receptors directly. The two most commonly prescribed are bromocriptine and pergolide. Researchers from the Mayo Clinic say that in some cases, patients taking pergolide (Permax) may experience damage to heart valves.