The rationale for people with most neurodegenerative disorders, including Parkinson's / Alzheimer's Disease, increasing glutathione is based on the evidence contained in the abstracts & articles below, which describe the role of oxidative stress & the decrease of Glutathione in the brain. Other supporting abstracts can also be found.
Glutathione plays a crucial role in mediating free radical damage & maintaining the oxidant/anti oxidant balance. Since the Brain consumes about 20% of the oxygen utilized by the body, the potential for oxidative stress is high. When glutathione is depleted this tilts the balance in favor of the oxidants - resulting in oxidative stress. Glutathione helps scavenge the free radicals and may slow down the degenerative process in Alzheimer's, Parkinson's Disease, as well as other neurodegenerative disorders.