Inclusion Criteria:  Physician-diagnosed Parkinson's disease Age 40-85 years Drug naïve or on stable dosage of PD medications with no plans to change for the duration of the study protocol Hoehn & Yahr stage < 4 in the clinical "ON" state Using laxatives (Miralax, Dulcolax, sennosides, etc.) regularly over the past 1 months (≥ 2 days per week) Complete informed consent in English Maintain habitual diet and exercise routine throughout study period Consume the study intervention twice per day during the eight-week intervention period Complete daily and weekly questionnaires, and all dietary recalls over approximately 10 weeks Fast (no food or drink, except plain water, coffee, or tea) at least 12 hours before each study visit  Exclusion Criteria:  Atypical or secondary Parkinsonism Underweight (BMI <18.5) Inability to swallow study supplement due to swallowing concerns Currently using a fiber supplement Use of another investigational product within 3 months of the screening visit Being treated for a physician-diagnosed GI disease or condition other than constipation, gastroparesis, gastroesophageal reflux disease, or diverticular disease