Arterial StiffnessCALGRAMNCT06544954
Prebiotic Effects of California Grapes on Gut Health and Cardiometabolic Health in Overweight Men and Women
A study testing Freeze-dried grape powder in people with Arterial Stiffness and Blood Pressure, run by University of California, Davis at 1 site in United States.
Trial 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. Read more about this study
- Who is it for?
- Ages 45 to 70 yearsHealthy volunteers can take part
- Conditions the study is for
- Arterial Stiffness, Blood Pressure, Dysbiosis
- What is being tested?
- Freeze-dried grape powder
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 40 participants
- Where
- 1 siteUnited States
- Study dates
- 7 May 2025to Jan 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 45 to 70 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- 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
Who cannot join
- 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
Show all 12Show fewer
- 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
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site, 1 recruiting
- Recruiting
Ragle Human Nutrition Center
Davis, California, 95616
Jody Randolph, 530-752-7620, jmrandolph@ucdavis.edu
Dragan Milenkovic, PhD
About this study
Official title: Assessing Prebiotic Effect of California Grape Consumption on Gut Microbiome and Impact on Intestinal Permeability, Vascular Function, and Systemic Inflammation in Over-weight Subjects: Differences in Effects Between Men and Women
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?
Read more
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
Read the detailed description
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- to 4-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.
Aim 1: Biomarkers to assess the permeability of the gut, including zonulin, lipopolysaccharide (LPS), LPS-binding protein (LBP), soluble CD14, and diamine oxidase (DAO), will be analyzed from blood samples. Gut microbiome profiling will be analyzed from 16S rRNA gene sequencing of fecal samples collected by participants at the beginning and end of each intervention arm.
Aim 2: Vascular function will be assessed by measuring blood pressure and pulse wave velocity. After 15 minutes of rest, blood pressure will be measured three times, with the average of the latter two recorded. Pulse wave velocity from the carotid to femoral artery will measure arterial stiffness. Inflammatory cytokines will be assayed from blood samples to include Th17 cytokines. Lipid panel and comprehensive metabolic panels will also be analyzed.
Aim 3: Sex differences in response to grape consumption will be assessed, including gut microbiome, gut permeability, vascular function, inflammation, lipid profile, and metabolomic pathways. Gender and time interactions will be determined to assess differences in trajectory of changes.
Aim 4: LC-MS will be used for untargeted metabolomics and lipidomics. Pathway analysis will assess metabolic pathways affected by grape consumption and their links to gut permeability, systemic inflammation, and vascular function.
- Being tested
- Freeze-dried grape powder, Placebo powder
- Keywords
- gut microbiome, nutrition, cardiometabolic health
- Medical subject headings
- Dysbiosis, Inflammation
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Freeze-dried grape powderDietary supplement
48 grams powder
Placebo powderOther
48 grams powder
| Study group | Role | What they receive |
|---|---|---|
| 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. Receives: 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. Receives: Dietary Supplement: Freeze-dried grape powder; Other: Placebo powder |
What is being measured
The primary outcome is the main question the study is designed to answer.
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
Measured: 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
Measured: 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
Measured: 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
Measured: 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
Measured: 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
Measured: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
Secondary outcomes (3)
Gut permeability marker Change from Baseline
bacterial DNA presence in blood from fasted blood samples collected in tubes with DNA/RNA shield when participants visit the clinic
Measured: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
Metabolomics and Lipidomics Change from Baseline
Pathway Analysis using data available from analysis of blood samples collected when participants visit the clinic
Measured: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
Global gene expression Change from Baseline
Microarrays of blood samples collected when participants visit the clinic
Measured: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted9 Aug 2024
- Study start7 May 2025
- Primary completionNov 2026 (estimated)
- Study completionJan 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Arterial StiffnessStudies of the same condition, open and under way.
- More trials run by University of California, DavisThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- 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.
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 40 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of California, Davis
- Sponsor type
- University, hospital or other
- Collaborators
- California Table Grape Commission
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06544954
- Sponsor's protocol ID
- 2172765
- Other IDs
- Proposal No 23-2586
- Acronym
- CALGRAM
- Status last verified
- Apr 2026
- First submitted
- 5 Aug 2024
- Last updated
- 13 Apr 2026
- Results posted
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 13 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Assessing Prebiotic Effect of California Grape Consumption on Gut Microbiome and Impact on Intestinal Permeability, Vascular Function, and Systemic Inflammation in Over-weight Subjects: Differences in Effects Between Men and Women
- ClinicalTrials.gov ID
- NCT06544954
- Acronym / sponsor ID
- CALGRAM / 2172765
- Keywords
- gut microbiome, nutrition, cardiometabolic health
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 40 participants (estimated)
- Lead sponsor
- University of California, DavisUniversity, hospital or other
- Collaborators
- California Table Grape Commission
- Study start
- 7 May 2025 (actual)
- Primary completion
- Nov 2026 (estimated)
- Study completion
- Jan 2027 (estimated)
- First posted
- 9 Aug 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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
Detailed description
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- to 4-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.
Aim 1: Biomarkers to assess the permeability of the gut, including zonulin, lipopolysaccharide (LPS), LPS-binding protein (LBP), soluble CD14, and diamine oxidase (DAO), will be analyzed from blood samples. Gut microbiome profiling will be analyzed from 16S rRNA gene sequencing of fecal samples collected by participants at the beginning and end of each intervention arm.
Aim 2: Vascular function will be assessed by measuring blood pressure and pulse wave velocity. After 15 minutes of rest, blood pressure will be measured three times, with the average of the latter two recorded. Pulse wave velocity from the carotid to femoral artery will measure arterial stiffness. Inflammatory cytokines will be assayed from blood samples to include Th17 cytokines. Lipid panel and comprehensive metabolic panels will also be analyzed.
Aim 3: Sex differences in response to grape consumption will be assessed, including gut microbiome, gut permeability, vascular function, inflammation, lipid profile, and metabolomic pathways. Gender and time interactions will be determined to assess differences in trajectory of changes.
Aim 4: LC-MS will be used for untargeted metabolomics and lipidomics. Pathway analysis will assess metabolic pathways affected by grape consumption and their links to gut permeability, systemic inflammation, and vascular function.
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 2
- Model description
- 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.
| Arm | Type | Receives |
|---|---|---|
| Grape, Then Placebo | Experimental | Dietary Supplement: Freeze-dried grape powder, Other: Placebo powderParticipants 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. |
| Placebo, Then Grape | Experimental | Dietary Supplement: Freeze-dried grape powder, Other: Placebo powderParticipants 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. |
Who may qualify
- Ages
- 45 to 70 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (5 listed)
- 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
Key exclusion criteria (12 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Freeze-dried grape powder48 grams powder | Dietary supplement | Grape, Then Placebo, Placebo, Then Grape |
| Placebo powder48 grams powder | Other | Grape, Then Placebo, Placebo, Then Grape |
Primary outcome
Arterial stiffness Change from Baseline
Time frame: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
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
Blood pressure Change from Baseline
Time frame: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
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
Gut microbiome composition Change from Baseline
Time frame: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
16S rRNA sequencing of stool samples collected by participants from home in fecal collection tubes filled with DNA/RNA shield
Gut permeability markers Change from Baseline
Time frame: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
ELISA (zonulin, LPS, LBP, sCD14, DAO) to assay fasted blood samples collected when participants visit the clinic
Systemic inflammatory markers Change from Baseline
Time frame: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
Luminex - Th17 inflammatory cytokines of fasted blood samples collected when participants visit the clinic
Lipid and metabolic profiles Change from Baseline
Time frame: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
Lipid panel, comprehensive metabolic panel of fasted blood samples collected when participants visit the clinic
3 secondary outcomes
Gut permeability marker Change from Baseline
Time frame: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
Metabolomics and Lipidomics Change from Baseline
Time frame: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
Global gene expression Change from Baseline
Time frame: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 13 Apr 2026.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Freeze-dried grape powder in people with Arterial Stiffness and Blood Pressure, run by University of California, Davis at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 12 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 13 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Dragan Milenkovic, PhD ((530) 219-5872, dmilenkovic@ucdavis.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Arterial stiffness Change from Baseline (time frame: Baseline (Visit 1), Week 3 (Visit 2), Week 9 (Visit 4)). The study lists 6 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 13 Apr 2026.