The Effect of Psyllium and Wheat Bran on Body Weight in People With Parkinson's Disease and Constipation Symptoms

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