Testing gut-bacteria capsules for constipation

Inclusion Criteria: 1. Participants who fulfill Chinese diagnostic criteria for PD (2016 edition), aged 40-75 years; 2. PD Hoehn-Yahr stage 1-3 3. Participants who have at least 2 of the following symptoms in the past 3 months and the symptoms have been present for at least 6 months: ① More than 25% of defecations are laborious; ② More than 25% of defecations consist of hard or lumpy stools; ③ More than 25% of defecations are accompanied by a sensation of incomplete evacuation; ④ More than 25% of defecations are accompanied by a sensation of anorectal obstruction; ⑤ More than 25% of defecations require manual assistance; ⑥ Less than 3 spontaneous bowel movements per week. 4. Have taken a stable dose of anti-Parkinson drugs, antidepressants and antipsychotics for at least 1 month; 5. Absence of red flags such as weight loss, hematochezia and exclusion of other diagnosis; 6. Have signed the informed consent and agree to participate in this study; Exclusion Criteria: 1. Parkinsonism-plus syndrome; 2. Stroke, brain trauma or epilepsy; 3. Have undergone surgery intervention due to PD; 4. Pregnant, planning pregnancy or lactating; 5. Psychiatric disorder or unable to cooperate with treatment and follow-up visit; 6. Immunodeficiency or treatment with immune-modulating medication; 7. Have undergone any abdominal surgery, with the exception of appendectomy, cholecystectomy, caesarean section and hysterectomy; 8. Presence of uncontrolled diabetes, hypertension, thyroid disease or other systemic disease; 9. Use of probiotics or antibiotics within 1 month prior to study entry; 10. Presence of severe diseases related to heart, brain, kidney and lung or concomitant malignancies;