One recently published clinical study tested the effects of the ketogenic diet on symptoms of Parkinson’s disease (VanItallie et al., 2005). In this uncontrolled study, Parkinson’s disease patients experienced a mean of 43% reduction in Unified Parkinson’s Disease Rating Scale scores after a 28-day exposure to the ketogenic diet. All participating patients reported moderate to very good improvement in symptoms. Further, as in Alzheimer’s disease, consumption of foods containing increased amounts of essential fatty acids has been associated with a lower risk of developing Parkinson’s disease (de Lau et al., 2005).

Source: Neuroprotective and disease-modifying effects of the ketogenic diet – PMC