Effects of Probiotic Supplementation on Gut Health, Immune Response, and Well-Being

This is a prospective, randomized, double-blind, placebo-controlled, singlecenter, two-arm, parallel-group exploratory study in 50 healthy adults with mild to moderate levels of perceived stress.

The study lasts a total of 9 weeks per participant with a 1-week run-in period followed by 8 weeks of supplementation. The study includes three visits to the study site: a screening visit, a pre-intervention visit (at the end of the run-in period), and a post-intervention visit after 8 weeks of supplementation. After providing written informed consent, participants will undergo screening to confirm eligibility. Screening assessments include demographic information, medical history, concomitant medication, body weight, height, body mass index, blood pressure, pulse, and assessment of chronic stress. A pregnancy test will be performed for female participants, as applicable.

Participants are randomly assigned to receive either the probiotic supplement or a matching placebo. Randomization will be stratified by sex. Participants will take one capsule once daily before or with dinner for 56 days.

The probiotic product contains fructooligosaccharides, selected probiotic bacterial strains, and vitamins. The placebo does not contain those active ingredients and is similar in appearance, taste and smell. Treatment allocation will remain blinded to participants and the study team involved in study assessments. Blood and stool samples will be collected before and after the intervention. Laboratory assessments will include markers related to gut barrier function, intestinal inflammation, gut microbiome composition, short-chain fatty acids, and systemic immune function. Further, participants will complete questionnaires assessing quality of life, health-related quality of life, depression, anxiety, stress, bloating, flatulence, stool consistency, and stool frequency. Safety will be evaluated by monitoring adverse events, blood pressure, and pulse. During the complete study duration, participants are instructed to maintain their usual lifestyle and diet.

Inclusion criteria

• Volunteer is healthy at the time of screening according to participant's own statements.
• TICS SSCS score ≥ 6.
• Male or female aged ≥18 and ≤65 years at the time of screening.
• BMI ≥18.5 and ≤29.9 kg/m².
• Volunteer is able and willing to comply with the study instructions.
• Volunteer is suitable for participation in the study according to the investigator/study personnel.
• Voluntary, written informed consent to participate in the study.

Exclusion criteria

• No command of local language.
• Currently diagnosed neurological or psychiatric disorders.
• Gastrointestinal disorders including irritable bowel syndrome (IBS), inflammatory bowel disease (IBD) or other conditions that might affect the gut environment.
• Contraindication or allergy to any ingredient in the verum or Placebo product.
• Use of drugs in the previous 4 weeks before the beginning of intervention.
• Use of laxatives and labelled pre#and probiotics in the previous 2 weeks before the beginning of intervention.
• Participation in another study with any investigational product within 30 days of screening, or less than five elimination half-lives after the last administration of the investigational product (whichever period is longer) or during the study.
• History of drug (recreational) or alcohol abuse.
• Bowel preparation for investigative procedures in the 4 weeks prior to screening.
• Surgical resection of any part of the bowel (excl. appendectomy).
• Pregnant or lactating female, or pregnancy planned during study period, or women of childbearing potential who are not using a medically approved form of contraception (at least three months prior to screening).
• Regular smoking.