Inclusion Criteria:  Age of 18 and upwards Diagnosis of idiopathic Parkinson's disease according to the Movement Disorder Society clinical diagnostic criteria Hoehn Yarh stage II-IV Diagnosis of constipation according to the ROME IV criteria and ≤ than 3 complete bowel movements per week  Exclusion Criteria:  Diagnosis or suspicion of other causes for parkinsonism Advanced-stage therapies (deep brain stimulation, intrajejunal levodopa infusion, and apomorphine subcutaneous infusion) Any inflammatory bowel disease or diseases of the colon Previous surgery on the gastrointestinal tract History of laxative abuse Ongoing artificial nutrition Regular use of probiotics Previous intolerance and/or adverse reactions to probiotics Previous use of Symprove Recent or current use of any antibiotics (within 4 weeks before the start of the study) Swallowing issues interfering with the safety intake of the probiotic/placebo Pregnancy or lactation Major systemic disease Any condition interfering with the ability to give the informed consent Enrolment in another simultaneous investigational trial