The invention provides a method for treating a subject suffering from early stage Parkinson's disease with a pharmaceutical formulation containing an olive polyphenol composition. The olive polyphenol composition includes hydroxytyrosol and at least one additional olive polyphenol, and the hydroxytyrosol represents about 40 wt. % to about 90 wt. % of the olive polyphenol composition. The formulation is administered to the subject within the context of a dosing regimen that provides a daily dosage of the olive polyphenol composition in the range of 30 mg to about 2500 mg. The invention additionally provides a method for reducing the dose of an antiparkinsonism drug used in the treatment of early stage Parkinson's disease, as well as a pharmaceutical formulation for treating early stage Parkinson's disease.