Cardiovascular DiseasesNCT05321277
Response of Cardiometabolic Biomarkers and Gut Microbiota to Walnut Consumption
A study testing Walnuts and No-nut diet in people with Cardiovascular Diseases, run by University of California, Davis at 1 site in United States.
Trial summary
The purpose of this research is to test if eating walnuts will cause any changes in blood lipids (like good and bad cholesterol, for example) and levels of inflammation in the blood, as well as changes in the bacteria living in the gut. Read more about this study
- Who is it for?
- Ages 45 to 70 years
- Conditions the study is for
- Cardiovascular Diseases
- What is being tested?
- Walnuts and No-nut diet
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 30 participants
- Where
- 1 siteUnited States
- Study dates
- 19 Apr 2022to Aug 2026
- 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
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Overweight and obese men and postmenopausal women between 45-70 years of age, BMI range of 25.0-39.9 kg/m2 and elevated LDL-C levels (130-189 mg/dL).
Who cannot join
- Adults unable to consent, individuals who are not yet adults (infants, children, teenagers), pregnant or lactating women, women planning to become pregnant in the next four months and prisoners will be specifically excluded.
- Additional exclusion criteria are listed below:
- Allergy to walnuts or other nuts
- Eating more than 25 grams of fiber per day, assessed by the Block Dietary-Fruit-Vegetable-Fiber Screener©
- Taking medications or supplements known to affect metabolism or gut microbiota composition (i.e. Metformin, statins, antibiotics within the past 3 months, fiber supplements, probiotics, and others)
- Documented chronic diseases including diabetes, renal or liver disease, metabolic syndrome, active cancer, MI or stroke, history of gastric bypass or GI disease (e.g. Crohn's Disease, Irritable Bowel Disease, diverticulosis, diverticulitis, etc.)
Show all 14Show fewer
- Smoker or living with a smoker, including vaporizer and/or electronic cigarettes.
- Illicit drug use, cannabis usage, or consuming >1 alcoholic drink/day
- Extreme dietary or exercise patterns
- Recent weight fluctuations (>10% in the last 6 months)
- Taking prescription lipid medications or supplements that may affect lipoprotein metabolism (i.e. >1 g of fish oil/day, antioxidant supplements)
- Taking exogenous hormones
- Poor venous access
- Unwillingness to comply with study protocols
Trial locations and contacts
1 site in 1 country.
United States1 site
Ragle Human Nutrition Center
Davis, California, 95616
About this study
The purpose of this research is to test if eating walnuts will cause any changes in blood lipids (like good and bad cholesterol, for example) and levels of inflammation in the blood, as well as changes in the bacteria living in the gut.
Read the detailed description
The purpose of this research is to test if eating walnuts will cause any changes in blood lipids (like good and bad cholesterol, for example) and levels of inflammation in the blood, as well as changes in the bacteria living in the gut. Overweight/obese adults between the ages of 45 and 70 yo with elevated LDL-C levels are eligible to participate. The study involves 5 visits (1 initial screening and 4 study visits) and will last about 10 weeks. There is a 1-week run-in period before starting the study, followed by two diet intervention periods each lasting 3 weeks, separated by a 3-week washout period.
Participation in this study will involve an initial 1-week run in period to become accustomed to the study diet. After this 1 week period, participants will be randomly selected to start either a walnut or a no-nut diet. During each phase of the study, participants will be asked to come to the University of California, Davis campus after a 10-12 hour overnight fast. At each visit, body measurements will be taken; blood, urine and fecal samples will be collected.
During the 10 weeks of the study, all nuts and nut-derived products will need to be avoided. The study will provide walnuts to be eaten at home for each intervention phase. Additionally, the investigators will ask that ellagitannin-rich foods, high-fiber and fermented foods be avoided in the diet. Detailed food diaries will be filled out and brought to study visits.
- Conditions
- Cardiovascular Diseases
- Being tested
- Walnuts, No-nut diet
- Keywords
- heart health, gut microbiota, Mediterranean diet, cardiometabolic health, gut health, diet
- Medical subject headings
- Cardiovascular Diseases
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
WalnutsDietary supplement
Participants will consume 56 g of walnuts daily for 3 weeks. Participants will also follow a diet devoid of ellagitannin-rich, high fiber, and fermented foods.
No-nut dietDietary supplement
Participants will exclude all nuts and nut-derived products; high-fiber, fermented and ellagitannin-rich foods will also be excluded.
| Study group | Role | What they receive |
|---|---|---|
| Walnut diet | Active comparator | Participants will consume 56 g of walnuts each day at home for 3 weeks. Receives: Dietary Supplement: Walnuts |
| No-nut diet | Active comparator | Participants will follow a no-nut diet for 3 weeks. Receives: Dietary Supplement: No-nut diet |
What is being measured
The primary outcome is the main question the study is designed to answer.
Assessing the influence of walnut consumption on blood lipid measurements.
Measure for changes in the levels of HDL and LDL in separated plasma; measured in units of mg/dL. Blood will be assessed for the fasting (baseline) sample at each of the 4 study visits.
Measured: Through study completion, an average of 10 weeks
Assessing the influence of walnut consumption on circulating inflammatory markers: PAI-1, VCAM-1 and ICAM-1.
Measure circulating inflammatory markers in separated plasma at each of the 4 study visits. Commercially available ELISA kits will be used: PAI-1, VCAM-1, ICAM-1.
Measured: Through study completion, an average of 10 weeks
Assessing the influence of walnut consumption on blood pressure.
Measure blood pressure (mmHg) before the start of drawing blood on study day protocols.
Measured: Through study completion, an average of 10 weeks
Secondary outcomes (5)
Assessing the influence of walnut consumption on fecal pH.
Measure fecal pH via pH meter at each of the 4 study visits.
Measured: Through study completion, an average of 10 weeks
Assessing the influence of walnut consumption on stool consistency.
Assess fecal consistency using Bristol Stool Scale at each of the 4 study visits. The scale runs from Type 1 (the lowest) to Type 7 (the highest). The desirable Type is either 3 or 4. Types 1 and 2 may be indicative of constipation, while Types 5, 6, and 7 may indicative diarrhea.
Measured: Through study completion, an average of 10 weeks
Assessing the influence of walnut consumption on fecal moisture.
Measure fecal moisture by weighing wt and vacuum dried feces in grams at each of the 4 study visits.
Measured: Through study completion, an average of 10 weeks
Assessing the influence of walnut consumption on the levels of gut inflammatory markers: Lipocalin-2 and calprotectin.
Measure fecal levels of Lipocalin-2 and calprotectin at each of the 4 study visits. Commercially available ELISA kits will be used: lipocalin-2, calprotectin.
Measured: Through study completion, an average of 10 weeks
Assessing the influence of walnut consumption on plasma and urine levels of walnut-derived metabolites - urolithins.
Measure urolithin levels in separated plasma and urine via metabolomics analysis at each of the 4 study visits.
Measured: Through study completion, an average of 10 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted11 Apr 2022
- Study start19 Apr 2022
- Primary completion11 Jun 2024
- Study completionAug 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Cardiovascular DiseasesStudies 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
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Enrolment
- 30 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of California, Davis
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05321277
- Sponsor's protocol ID
- 1867437
- Status last verified
- Feb 2026
- First submitted
- 1 Apr 2022
- Last updated
- 10 Feb 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 10 Feb 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Response of Cardiometabolic Biomarkers and Gut Microbiota to Walnut Consumption
- ClinicalTrials.gov ID
- NCT05321277
- Acronym / sponsor ID
- 1867437
- Conditions
- Cardiovascular Diseases
- Keywords
- heart health, gut microbiota, Mediterranean diet, cardiometabolic health, gut health, diet
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 30 participants (actual)
- Lead sponsor
- University of California, DavisUniversity, hospital or other
- Study start
- 19 Apr 2022 (actual)
- Primary completion
- 11 Jun 2024 (actual)
- Study completion
- Aug 2026 (estimated)
- First posted
- 11 Apr 2022 (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 purpose of this research is to test if eating walnuts will cause any changes in blood lipids (like good and bad cholesterol, for example) and levels of inflammation in the blood, as well as changes in the bacteria living in the gut.
Detailed description
The purpose of this research is to test if eating walnuts will cause any changes in blood lipids (like good and bad cholesterol, for example) and levels of inflammation in the blood, as well as changes in the bacteria living in the gut. Overweight/obese adults between the ages of 45 and 70 yo with elevated LDL-C levels are eligible to participate. The study involves 5 visits (1 initial screening and 4 study visits) and will last about 10 weeks. There is a 1-week run-in period before starting the study, followed by two diet intervention periods each lasting 3 weeks, separated by a 3-week washout period.
Participation in this study will involve an initial 1-week run in period to become accustomed to the study diet. After this 1 week period, participants will be randomly selected to start either a walnut or a no-nut diet. During each phase of the study, participants will be asked to come to the University of California, Davis campus after a 10-12 hour overnight fast. At each visit, body measurements will be taken; blood, urine and fecal samples will be collected.
During the 10 weeks of the study, all nuts and nut-derived products will need to be avoided. The study will provide walnuts to be eaten at home for each intervention phase. Additionally, the investigators will ask that ellagitannin-rich foods, high-fiber and fermented foods be avoided in the diet. Detailed food diaries will be filled out and brought to study visits.
Study design
- Primary purpose
- Basic science
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Walnut diet | Active comparator | Dietary Supplement: WalnutsParticipants will consume 56 g of walnuts each day at home for 3 weeks. |
| No-nut diet | Active comparator | Dietary Supplement: No-nut dietParticipants will follow a no-nut diet for 3 weeks. |
Who may qualify
- Ages
- 45 to 70 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (1 listed)
- Overweight and obese men and postmenopausal women between 45-70 years of age, BMI range of 25.0-39.9 kg/m2 and elevated LDL-C levels (130-189 mg/dL).
Key exclusion criteria (14 listed)
- Adults unable to consent, individuals who are not yet adults (infants, children, teenagers), pregnant or lactating women, women planning to become pregnant in the next four months and prisoners will be specifically excluded.
- Allergy to walnuts or other nuts
- Eating more than 25 grams of fiber per day, assessed by the Block Dietary-Fruit-Vegetable-Fiber Screener©
- Taking medications or supplements known to affect metabolism or gut microbiota composition (i.e. Metformin, statins, antibiotics within the past 3 months, fiber supplements, probiotics, and others)
- Documented chronic diseases including diabetes, renal or liver disease, metabolic syndrome, active cancer, MI or stroke, history of gastric bypass or GI disease (e.g. Crohn's Disease, Irritable Bowel Disease, diverticulosis, diverticulitis, etc.)
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 |
|---|---|---|
| WalnutsParticipants will consume 56 g of walnuts daily for 3 weeks. Participants will also follow a diet devoid of ellagitannin-rich, high fiber, and fermented foods. | Dietary supplement | Walnut diet |
| No-nut dietParticipants will exclude all nuts and nut-derived products; high-fiber, fermented and ellagitannin-rich foods will also be excluded. | Dietary supplement | No-nut diet |
Primary outcome
Assessing the influence of walnut consumption on blood lipid measurements.
Time frame: Through study completion, an average of 10 weeks
Measure for changes in the levels of HDL and LDL in separated plasma; measured in units of mg/dL. Blood will be assessed for the fasting (baseline) sample at each of the 4 study visits.
Assessing the influence of walnut consumption on circulating inflammatory markers: PAI-1, VCAM-1 and ICAM-1.
Time frame: Through study completion, an average of 10 weeks
Measure circulating inflammatory markers in separated plasma at each of the 4 study visits. Commercially available ELISA kits will be used: PAI-1, VCAM-1, ICAM-1.
Assessing the influence of walnut consumption on blood pressure.
Time frame: Through study completion, an average of 10 weeks
Measure blood pressure (mmHg) before the start of drawing blood on study day protocols.
5 secondary outcomes
Assessing the influence of walnut consumption on fecal pH.
Time frame: Through study completion, an average of 10 weeks
Assessing the influence of walnut consumption on stool consistency.
Time frame: Through study completion, an average of 10 weeks
Assessing the influence of walnut consumption on fecal moisture.
Time frame: Through study completion, an average of 10 weeks
Assessing the influence of walnut consumption on the levels of gut inflammatory markers: Lipocalin-2 and calprotectin.
Time frame: Through study completion, an average of 10 weeks
Assessing the influence of walnut consumption on plasma and urine levels of walnut-derived metabolites - urolithins.
Time frame: Through study completion, an average of 10 weeks
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 10 Feb 2026.
- Individual participant dataSharing planned: No
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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. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Walnuts and No-nut diet in people with Cardiovascular Diseases, 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 1 inclusion and 14 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: under way, not looking for participants, as of the sponsor's last update on 10 Feb 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?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Assessing the influence of walnut consumption on blood lipid measurements. (time frame: Through study completion, an average of 10 weeks). The study lists 3 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 10 Feb 2026; AzTrials last refreshed its copy on 8 Nov 2026.