Grape Impact on Human Gut Microbiome

Inclusion Criteria

• Healthy adults between the ages of 45 and 65 years old
• Body Mass Index (BMI) within the range of 18.5 to 25.9 kg/m²
• Willing and able to provide informed consent
• Agreement to maintain usual dietary patterns throughout the study, except for the provided study powder
• Agreement to avoid exclusion criteria (below) during the study period
• Able and willing to collect and mail a stool sample during the microbiome screening phase and, if enrolled in the intervention phase, and at the three defined study timepoints
• For enrollment into the intervention phase, meeting pre-specified microbiome eligibility criteria based on the screening stool sample, as defined in the study protocol.

Exclusion Criteria

• Antibiotic use within 6 months prior to enrollment, or any planned antibiotic use during the study
• Recent initiation of or dose change in any medication or supplement within 3 months prior to enrollment, or planned initiation or dose change during the study
• Initiation or change of probiotic, prebiotic, or synbiotic supplements during the study. Existing long-term stable probiotic use is permitted
• Current or recent (within 3 months) systemic corticosteroid, biologic, DMARD, chemotherapy, or other immunosuppressive therapy; regular NSAID use (more than 2 doses per week); or planned initiation of any of the above during the study
• Active inflammatory bowel disease, irritable bowel syndrome with current symptoms, celiac disease, microscopic colitis, active diverticulitis, or acute gastrointestinal infection within 3 months; any history of C. difficile infection; or prior bariatric surgery or bowel resection
• Uncontrolled or unstable chronic disease, including but not limited to uncontrolled diabetes (HbA1c >8%), chronic hepatitis B or C, cirrhosis, moderate-to-severe chronic kidney disease (eGFR <60), active or recent (within 5 years) malignancy, solid organ or bone marrow transplant, or uncontrolled cardiovascular or psychiatric illness
• Planned major change in diet, physical activity, or lifestyle during the study period; recent significant weight change (>5% in 3 months); or current adherence to an extreme dietary pattern (strict vegan, ketogenic, carnivore, or very-low-carb) maintained for more than 3 months
• Habitual high polyphenol intake, including daily consumption of more than 2 servings of berries, more than 500 mL of red wine, more than 4 cups of tea, or regular consumption of pomegranate, grape juice, or dark chocolate more than 3 times per week, as assessed by screening food-frequency questionnaire
• Heavy alcohol use (more than 14 drinks per week), current tobacco use, or daily cannabis use
• Known grape allergy or sensitivity; pregnancy, planned pregnancy, or breastfeeding during the study; current participation in other interventional clinical trials; or any condition that, in the investigator's judgment, would compromise study participation, compliance, or data interpretation