Phase 2 Trial of Tributyrin in People With Parkinson's Disease and Cognitive Impairments

Inclusion Criteria: * Male or Female, age 45 years and over. * Diagnosis of PD based on the United Kingdom Parkinson's Disease Society Brain Bank Diagnostic Research Criteria (Hughes et al., 1992) AND evidence of mild cognitive impairment (Litvan et al., 2012) OR Diagnosis of PDD (Emre et al., 2007). * If taking cholinesterase inhibitors, benzodiazepines, memantine, or anti-psychotic medications, on a stable regimen as defined by no medication changes for these drugs in prior 4 weeks. Exclusion Criteria: * Evidence of atypical parkinsonism. * Contra-indications to MR imaging including but not limited to pacemakers, aneurysm clips, intraocular metal, cochlear implant, or severe claustrophobia. * Evidence of large vessel stroke or mass lesion on MRI. * Regular use of typical anti-cholinergic drugs. * Recent history of significant, uncontrolled GI disease such as GERD, colorectal cancer. * Significant metabolic or uncontrolled medical comorbidity. * Pregnant or nursing. * Suicidal ideation, as indicated by a response of 2 or 3 on question 9 of the Beck Depression Inventory. * Any other condition or criterion that would preclude safe and meaningful participation in the study.