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Effects of Walnuts on Endothelial Function in Overweight Adults With at Least One Factor of Metabolic Syndrome (Walnut2)

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ClinicalTrials.gov Identifier: NCT01413646
Recruitment Status : Completed
First Posted : August 10, 2011
Last Update Posted : August 2, 2019
California Walnut Commission
Information provided by (Responsible Party):
David Katz, MD, Griffin Hospital

Brief Summary:
The purpose of this study is to examine the effects of walnut consumption on endothelial function and lipid markers in overweight patients with at least one factor of metabolic syndrome as compared to the control group.

Condition or disease Intervention/treatment Phase
Metabolic Syndrome Dietary Supplement: Walnut Supplementation Dietary Supplement: No walnut supplementation Not Applicable

Detailed Description:

The prevalence of obesity in both adults and children in the United States has increased significantly over the past 50 years. More than 66% of adults in the US are now overweight or obese and at least 17% of children in the population at large are now considered overweight.Obesity may be a factor predisposing patients to a myriad of comorbidities that increase the associated mortality rate.Several large prospective trials have documented that obesity is an independent risk factor for mortality from cardiovascular disease (CVD). Considering the major metabolic and biochemical changes that occur in obesity, such as atherogenic dyslipidemia, insulin resistance and hyperinsulinemia, endothelial dysfunction, and chronic inflammatory and prothrombotic states, obesity plays a role in the pathogenesis of systemic atherosclerosis and its clinical complications.

Walnuts are rich in alpha-linolenic acid, an essential omega-3 fatty acid, L-arginine and antioxidants. Polyunsaturated fatty acids and antioxidants have anti-oxidative effects and are thought to help preserve the endothelium's capacity to generate nitric oxide (NO), which acts to promote vasodilation, stabilize platelets, and promote the anti-inflammatory abilities of the endothelium. Evidence of this anticipated effect would have implications for strategies to prevent or retard type 2 diabetes mellitus and cardiovascular disease. Endothelial function testing using high frequency ultrasound imaging of the brachial artery to assess endothelium-dependent flow-mediated dilatation (FMD) offers a non-invasive, uniquely valuable means of assessing aggregated influences on cardiac risk by gauging a physiologic response of the vascular endothelium. Proposed, therefore, is a randomized, controlled, cross-over clinical trial, to assess the effects of walnuts on endothelial function in overweight adults with elevated waist circumference and at least one risk factor of metabolic syndrome.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 40 participants
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)
Primary Purpose: Prevention
Official Title: Effects of Walnuts on Endothelial Function in Overweight Adults With at Least One Factor of Metabolic Syndrome: A Randomized, Controlled, Cross-Over Trial
Study Start Date : February 2010
Actual Primary Completion Date : October 2010
Actual Study Completion Date : December 2010

Resource links provided by the National Library of Medicine

Arm Intervention/treatment
Experimental: Walnut Supplementation
Eight weeks with walnut supplementation to an ad lib diet
Dietary Supplement: Walnut Supplementation
Eight weeks of walnut supplementation

Placebo Comparator: 2
Eight weeks ad lib diet without walnut supplementation
Dietary Supplement: No walnut supplementation
Eight weeks without walnut supplementation

Primary Outcome Measures :
  1. Endothelial function [ Time Frame: 8 weeks ]
    Brachial artery flow mediated dilation (FMD)

Secondary Outcome Measures :
  1. Weight [ Time Frame: 8 weeks ]
  2. Waist circumference [ Time Frame: 8 weeks ]
  3. Fasting lipid panel [ Time Frame: 8 weeks ]
    Total cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, triglyceride level, cholesterol / high density lipoprotein cholesterol ratio

  4. Fasting blood glucose [ Time Frame: 8 weeks ]
  5. Fasting insulin [ Time Frame: 8 weeks ]
  6. Blood pressure [ Time Frame: 8 weeks ]

Information from the National Library of Medicine

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Ages Eligible for Study:   25 Years to 75 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Male and female age 25-75 years
  • Non-smoker
  • Overweight (BMI ≥ 25) with central adiposity as indicated by waist circumference (102 cm. in men / 88 cm. in women)
  • Meet one risk factor of the metabolic syndrome.

    • blood pressure > 130/85 or taking antihypertensive medication

      • fasting plasma glucose (FPG) >100 mg/dL (6.1 mmol/L)
      • fasting serum triglycerides level (TG) > 150 mg/dL (1.69 mmol/L)
      • fasting high-density lipoprotein (HDL) cholesterol < 40 mg/dL (1.04 mmol/L)in men, and < 50 mg/dL (1.29 mmol/L) in women.

Exclusion Criteria:

  • Anticipated inability to complete or comply with study protocol
  • Use of lipid-lowering or antihypertensive medications or aspirin unless stable on medication for at least 3 months and willing to refrain from taking medication for 12 hours prior to EF scanning
  • Preexisting cardiovascular disease (including symptomatic coronary artery disease (CAD), myocardial infarction, angina pectoris, anginal equivalent, peripheral vascular disease, congestive heart failure, carotid stenosis)
  • Severe hypertension (systolic blood pressure >180mmHg or diastolic blood pressure >105mmHg), even if well-controlled by medication.
  • Diagnosed diabetes mellitus
  • Regular use of multivitamins, Vitamin C, Vitamin E, fish oil, flax seed oil, omega-3 fatty acids, CoQ10, fiber supplements, garlic pills, arginine, red yeast rice, and any kind of antioxidant and unwillingness to discontinue supplementation for at least 4 weeks prior to study initiation and for study duration
  • Allergic to walnuts or any other nuts
  • Diagnosed eating disorder
  • On any specific diet, weight control diet, vegan diet
  • Any rheumatologic disease requiring regular use of NSAIDs or alternative medications
  • Regular use of fiber supplements
  • Regular use of vasoactive medication (including glucocorticoids, antineoplastic agents, psychoactive agents, or bronchodilators), and anticoagulant drugs (including Coumadin, plavix )
  • Diagnosed sleep apnea
  • Substance abuse (chronic alcoholism, other chemical dependency)
  • Any unstable medical condition that would limit the ability of a subject to participate fully in the trial (e.g., cancer, AIDS, tuberculosis, psychotic disorder)
  • Current or impending pregnancy

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT01413646

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United States, Connecticut
Yale-Griffin Prevention Research Center
Derby, Connecticut, United States, 06418
Sponsors and Collaborators
Griffin Hospital
California Walnut Commission
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Principal Investigator: David L. Katz, MD, MPH Yale-Griffin Prevention Research Center
Publications automatically indexed to this study by ClinicalTrials.gov Identifier (NCT Number):
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Responsible Party: David Katz, MD, PRINCIPAL INVESTIGATOR, Griffin Hospital
ClinicalTrials.gov Identifier: NCT01413646    
Other Study ID Numbers: 2009-15
First Posted: August 10, 2011    Key Record Dates
Last Update Posted: August 2, 2019
Last Verified: July 2019
Keywords provided by David Katz, MD, Griffin Hospital:
endothelial function
Additional relevant MeSH terms:
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Metabolic Syndrome
Pathologic Processes
Body Weight
Insulin Resistance
Glucose Metabolism Disorders
Metabolic Diseases