Prebiotic Effects of California Grapes on Gut Health and Cardiometabolic Health in Overweight Men and Women

NCT06544954 | Recruiting

• 2 other identifiers: 2172765Proposal No 23-2586
• Study Type: interventional
• Target: 40
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this clinical trial is to assess the impact of table grape consumption on gut microbiome, intestinal permeability, systemic inflammation, and vascular function in healthy overweight men and women aged 45-70 years. The main questions it aims to answer are:

• Does daily grape intake alter intestinal microbiome composition and intestinal permeability?
• Are changes in gut microbiota and intestinal permeability correlated with changes in cardiometabolic risk factors (inflammation, vascular function, lipid profiles)?
• Does response to grape intake on gut microbiota, intestinal permeability, cardiometabolic and inflammatory markers differ between men and women?
• Are metabolic pathways modified by grape consumption able to explain the link between gut health and cardiometabolic factors? Researchers will compare freeze-dried grape powder to placebo powder to see if grape powder improves cardiometabolic risk factors. Participants will
• Consume the powder dissolved in water twice daily for 3 weeks
• Follow their usual diet, modified to limit polyphenol-rich foods
• Visit the clinic at the beginning and end of the intervention for vascular measurements and blood sample collection
• Complete a 3-day 24-hour dietary recall and collect stool sample before each visit

Conditions

Arterial Stiffness; Blood Pressure; Dysbiosis; Inflammation; Permeability; Increased

Keywords

gut microbiome; nutrition; cardiometabolic health

Outcome Measures

Primary Outcomes (6)

• Arterial stiffness Change from Baseline

  Pulse Wave Velocity (PWV) from carotid to femoral artery after 5 minutes rest; PWV is an established index of aortic stiffness using a validated non-invasive device that allows online pulse wave recording and automatic PWV calculation

  Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)

• Blood pressure Change from Baseline

  Average of latter 2 of 3 total measures (5 minutes apart) after 15 minutes of rest in a quiet room; SphygmoCor XCEL device will be used with participants in the seated position

  Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)

• Gut microbiome composition Change from Baseline

  16S rRNA sequencing of stool samples collected by participants from home in fecal collection tubes filled with DNA/RNA shield

  Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)

• Gut permeability markers Change from Baseline

  ELISA (zonulin, LPS, LBP, sCD14, DAO) to assay fasted blood samples collected when participants visit the clinic

  Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)

• Systemic inflammatory markers Change from Baseline

  Luminex - Th17 inflammatory cytokines of fasted blood samples collected when participants visit the clinic

  Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)

• Lipid and metabolic profiles Change from Baseline

  Lipid panel, comprehensive metabolic panel of fasted blood samples collected when participants visit the clinic

  Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)

Secondary Outcomes (3)

• Gut permeability marker Change from Baseline

  Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)

• Metabolomics and Lipidomics Change from Baseline

  Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)

• Global gene expression Change from Baseline

  Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)

Study Arms (2)

Grape, Then Placebo

EXPERIMENTAL

Participants consume 48 grams of freeze-dried grape powder (dissolved into water) twice daily for 3 weeks. After a washout period of at least 3 weeks, participants then consume 48 grams of placebo powder matching grape powder (dissolved into water) twice daily for 3 weeks.

Dietary Supplement: Freeze-dried grape powder; Other: Placebo powder

Placebo, Then Grape

EXPERIMENTAL

Participants consume 48 grams of placebo powder matching grape powder (dissolved into water) twice daily for 3 weeks. After a washout period of at least 3 weeks, participants then consume 48 grams of freeze-dried grape powder (dissolved into water) twice daily for 3 weeks.

Dietary Supplement: Freeze-dried grape powder; Other: Placebo powder

Interventions

Freeze-dried grape powder DIETARY_SUPPLEMENT

48 grams powder

Grape, Then Placebo; Placebo, Then Grape

Placebo powder OTHER

48 grams powder

Grape, Then Placebo; Placebo, Then Grape

Eligibility Criteria

• Age: 45 Years - 70 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• post-menopausal women (cessation of menstruation for minimum two years)
• overweight and obese (BMI between 25-35 kg/m2)
• stable treatment for type 2 diabetes or metabolic syndrome
• ability to understand the intervention concept and written consent to participate
• willingness to accept randomization, undergo testing and intervention procedures, and deliver stool and blood samples

You may not qualify if:

• menopausal hormone replacement therapy started within less than 6 months
• antibiotics, prebiotics within last 3 months
• antidiabetic treatment involving insulin (for type 1 diabetes)
• vegetarian/vegan and not able to follow modified diet
• any serious medical condition including but not limited to coronary artery disease, uncontrolled hypertension, stroke, congestive heart failure, insulin-dependent diabetes, liver disease, active cancer and anemia
• psychiatric disease that interferes with the understanding and implementation of the intervention
• history of eating disorders such as bulimia nervosa, anorexia nervosa, severe binge eating disorder in the last 5 years
• history of substance abuse or alcohol abuse
• involvement in a weight loss intervention program (including anti-obesity medication) within last 3 months or have had bariatric surgery
• current smokers (within last 180 days)
• use of dietary supplements containing polyphenols in the past 1 month
• strenuous exercise greater than 10 hours per week

Sponsors & Collaborators

• University of California, Davis: lead
• California Table Grape Commission: collaborator

Study Sites (1)

Ragle Human Nutrition Center

Davis, California, 95616, United States

RECRUITING

MeSH Terms

Conditions

Dysbiosis; Inflammation

Condition Hierarchy (Ancestors)

Pathologic Processes; Pathological Conditions, Signs and Symptoms

Central Study Contacts

Dragan Milenkovic, PhD

CONTACT

(530) 219-5872; dmilenkovic@ucdavis.edu

Shannon H Trinh, MS, RD

CONTACT

(408) 802-9356; shtrinh@ucdavis.edu

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Masking Details: Freeze-dried grape powder or placebo powder packets labeled "A" and "1".
• Purpose: PREVENTION
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: Participants will limit intake of grapes and other polyphenol-rich foods while following their usual diet during the 1-week run-in period before the start of the intervention. They will be randomized to start with either grape or placebo powder for 3 weeks, consuming 48 grams of freeze-dried grape powder or placebo dissolved in water twice daily. Compliance will be assessed with three 24-hour dietary recalls using ASA24 and follow-up contact. After a 3-week washout period, participants will crossover to the other intervention. Study outcomes and anthropometry will be measured on the first and last days of each intervention arm, with the study lasting approximately 10-11 weeks for participants.

Study Record Dates

• First Submitted: August 5, 2024
• First Posted: August 9, 2024
• Study Start: May 7, 2025
• Primary Completion (Estimated): November 1, 2026
• Study Completion (Estimated): January 1, 2027
• Last Updated: April 13, 2026

Record last verified: 2026-04

Locations

US (1)