The goal of this clinical trial is to evaluate the effect of probiotic and prebiotic supplementation in individuals with chronic spinal cord injury experiencing gastrointestinal complaints.

The main questions this trail aims to answer are:

• what are the effects of the supplementation on gastrointestinal symptoms?
• what are the effects of the supplementation on gut microbiome composition?
• what are the effects of the supplementation on inflammatory serum markers?
• what are the effects of the supplementation on gastrointestinal transit time?

Participants will:

• take either the probiotic or prebiotic supplement daily for eight weeks, followed by a four-week "wash-out period" (= no intake of either supplement) and a subsequent eight-week intake of the other supplement.
• visit the study center for four appointments, during which various measurements will be performed.

Inclusion Criteria (at screening):

• Age: ≥ 18 years
• Sex: male and female.
• Chronic SCI (>1 year post-injury)
• Individuals with para- and tetraplegia (American Spinal Cord Injury (ASIA) Impairment Scale (AIS) score A-D)
• Having significant gastrointestinal complaints, indicated with "yes" at screening and by a GIQLI questionnaire score below 110 at baseline
• Signed written informed consent

Exclusion Criteria (at screening):

• Antibiotic use within the last four weeks before starting the study
• Major dietary changes within the last four weeks before starting the study, such as initiating a vegan or ketogenic diet
• Presence of clinically relevant medical conditions, including Crohn's disease, diagnosed eating or gastrointestinal disorders, assessed on an individual basis
• Intake of significant concomitant medication, including immunomodulating therapy, mesalazines, or steroids, assessed on an individual basis
• Concurrent participation in other clinical trials investigating or potentially affecting GI health
• Insufficient German language skills to follow the study procedures
• Pregnancy (anamnestic)