Grape Impact on Human Gut Microbiome

High-Resolution Assessment of California Table Grape Consumption on the Human Gut Microbiome-Immune Axis

This is a bio-specimen analysis and dietary intervention study that will examine whether the daily consumption of California table grape powder significantly modulates the gut microbiome and systemic immune profiles in healthy adults. The primary objective is to characterize longitudinal changes in microbial strains, metabolites, and immune markers following a 4-week grape intervention compared to a placebo. Methods include a screening of up to 300 individuals to evaluate pre-specified microbiome eligibility criteria, followed by a randomized, double-blind, placebo-controlled, parallel-group design where up to 40 participants will provide fecal and blood samples for high-resolution metagenomic sequencing and LC-MS/MS metabolomics at baseline, mid-study, and post-washout. Participants who meet the microbiome screening and other study eligibility criteria may be invited to participate in the intervention phase; participation in the screening phase does not guarantee enrollment in the intervention phase.

Study Overview

• Status: Not yet recruiting
• Conditions: Gut Microbiomes
• Intervention / Treatment: Dietary supplement: Grape Powder; Other: Placebo Powder

Detailed Description

The human gut microbiome consists of trillions of microorganisms that are essential to host metabolism, immune system regulation, and the maintenance of disease resistance. Recent findings indicate that dietary changes can rapidly and significantly alter the composition of these microbial communities, leading to substantial effects on the host's overall physiology. Foods rich in polyphenols are highly effective at modulating this environment because they possess selective antimicrobial properties and exert beneficial prebiotic effects on the resident microbiota.

Polyphenol-rich foods beneficially modulate the human gut microbiome with downstream metabolic and immune effects. California table grapes contain a complex mixture of phenolics, resveratrol, flavans, flavonols, and anthocyanins, making them ideal candidates for investigating gastrointestinal and immune health. However, previous grape-microbiome studies have been limited by small sample sizes (n=21-29), short durations (2 weeks), low-resolution microbiome technologies (16S profiling), and failure to measure corresponding inflammatory or immune biomarkers.

This project will first conduct a microbiome screening phase in up to 300 healthy adults to identify individuals who meet pre-specified microbiome and other study eligibility criteria. Eligible individuals may then be invited to participate in a rigorous, multi-omic pilot study using standardized freeze-dried grape powder to determine how daily grape consumption modulates the gut microbiome-immune axis in up to 40 healthy adults. The study team will employ state-of-the-art metagenomic sequencing to achieve high-resolution microbiome profiling; metabolomic analysis; and immune biomarker profiling to assess gastrointestinal inflammation.

Specific Aims

Overarching Goal: To build on our unique expertise in high-resolution microbiome analyses to conduct a rigorous, multi-omic pilot study determining how daily consumption of California table grape powder modulates the human gut microbiome-immune axis in healthy adults.

Hypothesis: Compared to a placebo, daily consumption of California table grape powder will beneficially modulate the gut microbiome by: (1) altering microbial composition; (2) shifting the fecal metabolome to increase grape-derived and microbial-derived anti-inflammatory compounds; and (3) reducing baseline biomarkers of gastrointestinal inflammation.

• Study Type: Interventional
• Enrollment (Estimated): 40
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Gang Fang, PhD; Phone Number: 212-659-1570; Email: gang.fang@mssm.edu
• Study Contact Backup: Name: Edward A Mead, PhD; Phone Number: 212-659-6844; Email: edward.mead@mssm.edu

Study Locations

• United States
  • New York
    • New York, New York, United States, 10029
      • Icahn School of Medicine at Mount Sinai
      • Contact: Gang Fang, PhD; Phone Number: 212-659-1570; Email: gang.fang@mssm.edu
      • Contact: Edward A Mead, PhD; Phone Number: 212-659-6844; Email: edward.mead@mssm.edu
      • Principal Investigator: Gang Fang, PhD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Grape Powder; Receive grape powder for consumption during intervention stage.	Dietary supplement: Grape Powder; 72 g of grape powder for daily consumption for 28 days.
Placebo Comparator: Control; Receive placebo control powder for consumption during intervention stage.	Other: Placebo Powder; 72 g of matching placebo for daily consumption for 28 days.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Long read sequencing	Sequencing DNA from fecal samples to identify bacteria. This will assess whether the grape powder induces a change in the abundance of beneficial species/decrease in harmful species, following treatment, compared to control. This will be quantitatively assessed via sequencing.	3 collections at T0 (after 3 weeks of dietary control), at week 4 (after grape or placebo powder daily), and at week 8 (after 4 weeks of returning back to normal diet)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fecal metabolites profile from LC-MS/MS	Fecal metabolites as measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS)	3 collections at T0 (after 3 weeks of dietary control), at week 4 (after grape or placebo powder daily), and at week 8 (after 4 weeks of returning back to normal diet)
Fecal calprotectin level measured by ELISA	Fecal calprotectin as measured by ELISA. Elevated levels of calprotectin are a sensitive indicator of mucosal irritation.	3 collections at T0 (after 3 weeks of dietary control), at week 4 (after grape or placebo powder daily), and at week 8 (after 4 weeks of returning back to normal diet)
Fecal albumin level measured by ELISA	Fecal albumin as measured by ELISA. Fecal albumin serves as a proxy for intestinal permeability, as its presence in the gut lumen suggests a leak across the epithelial barrier.	3 collections at T0 (after 3 weeks of dietary control), at week 4 (after grape or placebo powder daily), and at week 8 (after 4 weeks of returning back to normal diet)
Fecal Lipocalin-2 measured by ELISA	Fecal Lipocalin-2 as measured by ELISA. Fecal Lipocalin-2 is produced by both epithelial and immune cells in response to bacterial stressors.	3 collections at T0 (after 3 weeks of dietary control), at week 4 (after grape or placebo powder daily), and at week 8 (after 4 weeks of returning back to normal diet)

Collaborators and Investigators

• Sponsor: Icahn School of Medicine at Mount Sinai
• Investigators: Principal Investigator: Gang Fang, PhD, Icahn School of Medicine at Mount Sinai

Study record dates

Study Major Dates

• Study Start (Estimated): September 1, 2026
• Primary Completion (Estimated): February 1, 2027
• Study Completion (Estimated): February 1, 2027

Study Registration Dates

• First Submitted: August 27, 2026
• First Submitted That Met QC Criteria: August 27, 2026
• First Posted (Actual): September 1, 2026

Study Record Updates

• Last Update Posted (Actual): September 1, 2026
• Last Update Submitted That Met QC Criteria: August 27, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: anti-inflammation; California Table Grapes; Third generation sequencing
• Additional Relevant MeSH Terms: whole grape extract
• Other Study ID Numbers: STUDY-26-00544; IN300001209 (Other Grant/Funding Number: California Table Grape Commission)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: All of the individual participant data collected during the trial, after deidentification.
• IPD Sharing Time Frame: Beginning 3 months and ending 5 years following article publication.
• IPD Sharing Access Criteria: Investigators whose proposed use of the data has been approved by an independent review committee ('learned intermediary') identified for this purpose. To achieve aims in the approved proposal.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; ANALYTIC_CODE

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No