Gut check: could targeted vitamin B2 boost aging microbiomes?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Individuals providing written informed consent for participation in the study and data processing 2. Female and males between 50 and 70 years of age 3. For females only: Menopausal as marked by at least 1 year since the last menstrual bleeding 4. Individuals with a BMI between 18.5 - 29.9 Kg/m2 5. Individuals with stable body weight (≤5% change) over the past 3 months prior to V1 6. Individuals with self-reported moderate bowel complaints in at least last 3 months prior to V1 7. Individuals with GSRS score suggestive of moderate bowel complaints, as assessed at V1, for the average condition over the 4 last weeks (all GSRS items have to be answered at V1): • indigestion score 3-5 or constipation score 3-5 or diarrhoea score 3-5 8. Individuals with a general good health, as determined by questioning, clinical examination and vital signs (blood pressure, pulse rate) by the investigator at V1 9. Individuals willing to avoid consuming gut microbiome modulating dietary supplements, prebiotic, probiotic, synbiotic or fibre-rich supplements during the entire study duration 10. Individuals willing to maintain current level of physical activity throughout the entire study duration 11. If individuals are taking chronic medications (e.g., antihypertensive medications), they must be willing and expected to maintain the same dosage throughout the study Exclusion Criteria: 1. Individuals who are hypersensitive/intolerant to any of the components of the Investigational product or the standardised diet addition (inulin) 2. Individuals who have taken systemic antibiotics within the previous 3 months prior to Baseline (V2) or are expected to be taking any during the study 3. Individuals who consumed microbiome modulating dietary supplements, prebiotic, probiotic, or fibre-rich supplements within 4 weeks prior to the baseline (V2) 4. Individuals who are currently regularly using systemic steroids, proton pump inhibitors, H2 blocker, antacids (however, sporadic use during the study if needed is allowed, but not within 8 hours before each visit), metformin if started less than 6 months prior to V1, or immunosuppressant medication. 5. Individuals who have a history of drug abuse in the previous 5 years and/or alcohol abuse at the time of enrolment (\>11 units/week for women; \>17 units/week for men; unit: approx. 125 mL of wine or similar / approx. 30 mL of spirits / approx. 280 mL beer or similar); Is currently in treatment for alcohol/substance abuse; Has been diagnosed with alcohol/substance abuse disorder) 6. Individuals who are a smoker or vaper 7. Individuals who are vegetarian or vegan 8. Individuals who have made any major dietary changes in the past 3 months prior to Baseline (V2) 9. Individuals who have planned major changes in the lifestyle (i.e., diet, dieting, exercise level, significant travel) during the duration of the study. 10. Individuals who have a currently present active eating disorder 11. Individuals with self-reported food allergy / intolerance (e.g., lactose, gluten, fructose), as determined by the study investigator 12. Clinical significance for any of screening laboratory test results from the blood draw at V1, as per investigator's judgement 13. Individuals with a self-reported fibre-rich regular diet, as per investigator's judgement 14. Individuals who have a (self-reported) gastrointestinal disorder/disease (e.g., chronic/recurrent diarrhoea, inflammatory bowel disorder, irritable bowel syndrome, diverticulosis, stomach or duodenal ulcers, bile acid malabsorption) or previous gastrointestinal surgery (such as bariatric surgery, colon specific surgical interventions etc.), which in the opinion of the investigator would impact the study outcomes 15. Individuals with GSRS assessed at V1 for the average condition over the 4 last weeks prior to V1 for any score (abdominal pain, reflux score, indigestion, constipation, diarrhoea) \>5 (all GSRS items have to be answered at V1) 16. Individuals who have severe or uncontrolled conditions such as type 2 diabetes (FBG ≥ 150 mg/dl from blood draw at V1), psychiatric disorder, respiratory or cardiac illness or any other condition which in the opinion of the investigator would impact the study outcomes 17. Individuals who have a history of any gastrointestinal cancer 18. Individuals who are severely immunocompromised 19. Individuals with alarm features in the past 3 months prior to V1 such as unintentional weight loss (≤5% change), fever, anorectal problems, blood in stool, vomiting 20. Individuals who, in the opinion of the investigator are considered to be poor attendees or unlikely for any reason to be able to comply with the study requirements 21. If Individuals have been in a recent experimental study, this must have been completed not less than 30 days prior to this study