HealthyWalBrainNCT07422220
Long-Term Effects of Walnut Consumption on Brain Function
A study testing Walnuts in people with Healthy and Brain Insulin Sensitivity, run by Maastricht University Medical Center at 1 site in Netherlands.
Trial summary
Rationale: Healthy foods, including mixed nuts, may improve brain function, which is essential for cognitive and metabolic health, and may contribute to improved food intake regulation. Read more about this study
- Who is it for?
- Ages 45 to 75 yearsHealthy volunteers can take part
- Conditions the study is for
- Healthy, Brain Insulin Sensitivity, Cerebral Blood Flow
- What is being tested?
- Walnuts
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 55 participants
- Where
- 1 siteNetherlands
- Study dates
- 1 Oct 2025to Aug 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 75 years
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Men and women, aged between 45-75 years
- Women postmenopausal: two or more years after last menstruation
- Waist circumference of ≥102 cm for men and ≥88 cm for women (abdominal obesity)
- Fasting plasma glucose < 7.0 mmol/L
- Fasting serum total cholesterol < 8.0 mmol/L
- Fasting serum triacylglycerol < 4.5 mmol/L
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- Systolic blood pressure < 160 mmHg and diastolic blood pressure < 100 mmHg
- Stable body weight (weight gain or loss < 3 kg in the past three months)
- Willingness to give up being a blood donor from 8 weeks before the start of the study, during the study and for 4 weeks after completion of the study
- No difficult venipuncture as evidenced during the screening visit
Who cannot join
- Allergy or intolerance to walnuts
- Left-handedness (effects on brain function differ between left- and right-handed adults)
- Current smoker, or smoking cessation < 12 months
- Diabetic patients
- Familial hypercholesterolemia
- Abuse of drugs
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- More than 3 alcoholic consumptions per day
- Use of products or dietary supplements (e.g., dietary fiber or antioxidant dietary supplements (vitamin C and E), fish or seaweed oil capsules) known to interfere with the main outcomes as judged by the principal investigators
- Use of medication to treat blood pressure, lipid, or glucose metabolism
- Use of an investigational product within another biomedical intervention trial within the previous 1-month
- Severe medical conditions that might interfere with the study, such as epilepsy, asthma, kidney failure or renal insufficiency, chronic obstructive pulmonary disease, inflammatory bowel diseases, auto inflammatory diseases, and rheumatoid arthritis
- Active cardiovascular disease like congestive heart failure or cardiovascular event, such as an acute myocardial infarction or cerebrovascular accident
- Contra-indications for MRI imaging (e.g., pacemaker, surgical clips/material in body, metal splinter in eye, claustrophobia)
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Netherlands1 site, 1 recruiting
- Recruiting
Maastricht University, Department of Nutrition and Movement Sciences
Maastricht, Limburg, 6200MD
Peter J. Joris, PhD, +31883887250, p.joris@maastrichtuniversity.nl
Linda J. Kehr, MSc, +31433883931, linda.kehr@maastrichtuniversity.nl
About this study
Official title: Long-Term Effects of Walnut Consumption on Brain Function in Men and Women With Abdominal Obesity
Rationale: Healthy foods, including mixed nuts, may improve brain function, which is essential for cognitive and metabolic health, and may contribute to improved food intake regulation. It is therefore important to investigate the specific effects of walnuts on cerebral blood flow responses before and after intranasal insulin administration, as well as their associated functional benefits. The investigators hypothesize that long-term walnut consumption improves vascular function and insulin-sensitivity in the brain, thereby enhancing cognitive performance and appetite control in abdominally obese men and women. Objective: The primary objectives are to investigate in abdominally obese adults the effects of 24-week walnut consumption on (regional) vascular function and insulin-sensitivity in the brain, while the investigators will also assess changes in cognitive performance and appetite-related brain reward activity (secondary objectives). Cerebral blood flow responses before (brain vascular function) and after the administration of intranasal insulin spray (brain insulin-sensitivity) will be quantified by the non-invasive gold standard magnetic resonance imaging (MRI)-perfusion method Arterial Spin Labeling (ASL). Study design: This intervention study will have a randomized, controlled parallel design. The total study duration will be 24 weeks. Study population: Fifty-five abdominally obese men and (postmenopausal) women (aged 45-75 years) without a history of cardiovascular diseases or complaints will participate. This study population is expected to have a decreased cerebral blood flow at baseline and are also at increased risk of cognitive impairment, allowing for improvement by the intervention. Intervention: Study participants will receive daily 50 g (about 15% of energy) of raw walnuts (walnut intervention) or no walnuts (control intervention) for 24 weeks. Main study parameters/endpoints: At baseline and after 24 weeks (follow-up), participants will visit the research facilities for assessments. The primary endpoint is the difference in the cerebral blood flow response before and after intranasal insulin administration between the walnut and control intervention. Cognitive performance will be assessed, while the investigators will also focus on appetite-related brain reward activity (secondary outcomes).
- Conditions
- Healthy, Brain Insulin Sensitivity, Cerebral Blood Flow, Brain Vascular Function, Satiety and Food Intake, Food Reward
- Being tested
- Walnuts
- Keywords
- Walnuts, Juglans, Brain vascular function, Brain insulin sensitivity, Satiety, Food reward mechanisms, Cognitive performance, Abdominal obesity, Cognitive decline, pCASL MRI, fMRI, CANTAB, Intranasal insulin, Food cues
- Medical subject headings
- Obesity, Abdominal, Cognitive Dysfunction
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
WalnutsDietary supplement
24-week consumption of 50 g/day of walnuts as part of a healthy diet according to the Dutch dietary guidelines
| Study group | Role | What they receive |
|---|---|---|
| Walnut | Experimental | Receive 50g walnuts per day Receives: Dietary Supplement: Walnuts |
| Control | No intervention | Does not receive walnuts and is supposed to refrain from nut consumption |
What is being measured
The primary outcome is the main question the study is designed to answer.
Cerebral blood flow (CBF) prior to and after application of intranasal insulin
CBF will be non-invasively measured using the gold-standard methodology pseudo-continuous arterial spin labeling magnetic resonance imaging (pCASL MRI)
Measured: From enrollment to the end of treatment at 24 weeks
Secondary outcomes (2)
Bloodoxygen level-dependent (BOLD) functional MRI (fMRI) activity to measure appetite-related brain reward activity
BOLD fMRI activity will be measured before and while participants watch food pictures
Measured: From enrollment to the end of treatment at 24 weeks
Cognitive performance
Cognitive performance measurement of the following cognitive domains: memory, executive function and psychomotor speed. Measurements will be performed using the Cambridge Neuropsychological Test Automated Battery (CANTAB).
Measured: From enrollment to the end of treatment at 24 weeks.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted19 Feb 2026
- Study start1 Oct 2025
- Primary completionAug 2027 (estimated)
- Study completionAug 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for HealthyStudies of the same condition, open and under way.
- 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
- Parallel groups
- Masking
- Triple blind
- Who is masked
- Care provider, Investigator, Outcomes assessor
- Enrolment
- 55 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Maastricht University Medical Center
- Sponsor type
- University, hospital or other
- Collaborators
- California Walnut Commission
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07422220
- Sponsor's protocol ID
- METC 25-018
- Acronym
- WalBrain
- Status last verified
- Jul 2026
- First submitted
- 2 Oct 2025
- Last updated
- 24 Jul 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 24 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Long-Term Effects of Walnut Consumption on Brain Function in Men and Women With Abdominal Obesity
- ClinicalTrials.gov ID
- NCT07422220
- Acronym / sponsor ID
- WalBrain / METC 25-018
- Conditions
- Healthy, Brain Insulin Sensitivity, Cerebral Blood Flow, Brain Vascular Function, Satiety and Food Intake, Food Reward
- Keywords
- Walnuts, Juglans, Brain vascular function, Brain insulin sensitivity, Satiety, Food reward mechanisms, Cognitive performance, Abdominal obesity
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 55 participants (estimated)
- Lead sponsor
- Maastricht University Medical CenterUniversity, hospital or other
- Collaborators
- California Walnut Commission
- Study start
- 1 Oct 2025 (actual)
- Primary completion
- Aug 2027 (estimated)
- Study completion
- Aug 2027 (estimated)
- First posted
- 19 Feb 2026 (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.
Rationale: Healthy foods, including mixed nuts, may improve brain function, which is essential for cognitive and metabolic health, and may contribute to improved food intake regulation. It is therefore important to investigate the specific effects of walnuts on cerebral blood flow responses before and after intranasal insulin administration, as well as their associated functional benefits. The investigators hypothesize that long-term walnut consumption improves vascular function and insulin-sensitivity in the brain, thereby enhancing cognitive performance and appetite control in abdominally obese men and women. Objective: The primary objectives are to investigate in abdominally obese adults the effects of 24-week walnut consumption on (regional) vascular function and insulin-sensitivity in the brain, while the investigators will also assess changes in cognitive performance and appetite-related brain reward activity (secondary objectives). Cerebral blood flow responses before (brain vascular function) and after the administration of intranasal insulin spray (brain insulin-sensitivity) will be quantified by the non-invasive gold standard magnetic resonance imaging (MRI)-perfusion method Arterial Spin Labeling (ASL). Study design: This intervention study will have a randomized, controlled parallel design. The total study duration will be 24 weeks. Study population: Fifty-five abdominally obese men and (postmenopausal) women (aged 45-75 years) without a history of cardiovascular diseases or complaints will participate. This study population is expected to have a decreased cerebral blood flow at baseline and are also at increased risk of cognitive impairment, allowing for improvement by the intervention. Intervention: Study participants will receive daily 50 g (about 15% of energy) of raw walnuts (walnut intervention) or no walnuts (control intervention) for 24 weeks. Main study parameters/endpoints: At baseline and after 24 weeks (follow-up), participants will visit the research facilities for assessments. The primary endpoint is the difference in the cerebral blood flow response before and after intranasal insulin administration between the walnut and control intervention. Cognitive performance will be assessed, while the investigators will also focus on appetite-related brain reward activity (secondary outcomes).
Study design
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Triple blind (care provider, investigator, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Walnut | Experimental | Dietary Supplement: WalnutsReceive 50g walnuts per day |
| Control | No intervention | –Does not receive walnuts and is supposed to refrain from nut consumption |
Who may qualify
- Ages
- 45 to 75 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (10 listed)
- Men and women, aged between 45-75 years
- Women postmenopausal: two or more years after last menstruation
- Waist circumference of ≥102 cm for men and ≥88 cm for women (abdominal obesity)
- Fasting plasma glucose < 7.0 mmol/L
- Fasting serum total cholesterol < 8.0 mmol/L
Key exclusion criteria (13 listed)
- Allergy or intolerance to walnuts
- Left-handedness (effects on brain function differ between left- and right-handed adults)
- Current smoker, or smoking cessation < 12 months
- Diabetic patients
- Familial hypercholesterolemia
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 |
|---|---|---|
| Walnuts24-week consumption of 50 g/day of walnuts as part of a healthy diet according to the Dutch dietary guidelines | Dietary supplement | Walnut |
Primary outcome
Cerebral blood flow (CBF) prior to and after application of intranasal insulin
Time frame: From enrollment to the end of treatment at 24 weeks
CBF will be non-invasively measured using the gold-standard methodology pseudo-continuous arterial spin labeling magnetic resonance imaging (pCASL MRI)
2 secondary outcomes
Bloodoxygen level-dependent (BOLD) functional MRI (fMRI) activity to measure appetite-related brain reward activity
Time frame: From enrollment to the end of treatment at 24 weeks
Cognitive performance
Time frame: From enrollment to the end of treatment at 24 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 24 Jul 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 Walnuts in people with Healthy and Brain Insulin Sensitivity, run by Maastricht University Medical Center at 1 site in Netherlands.
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 10 inclusion and 13 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 24 Jul 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 Netherlands. 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 Peter J. Joris, PhD (+31883887250, p.joris@maastrichtuniversity.nl), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Cerebral blood flow (CBF) prior to and after application of intranasal insulin (time frame: From enrollment to the end of treatment at 24 weeks). 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 24 Jul 2026.