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

This study has been completed.
California Walnut Commission
Information provided by:
Griffin Hospital Identifier:
First received: July 11, 2011
Last updated: August 9, 2011
Last verified: August 2011
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 Intervention
Metabolic Syndrome
Dietary Supplement: Walnut Supplementation
Dietary Supplement: No walnut supplementation

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: 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

Resource links provided by NLM:

Further study details as provided by Griffin Hospital:

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

Secondary Outcome Measures:
  • Weight [ Time Frame: 8 weeks ]
  • Waist circumference [ Time Frame: 8 weeks ]
  • 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

  • Fasting blood glucose [ Time Frame: 8 weeks ]
  • Fasting insulin [ Time Frame: 8 weeks ]
  • Blood pressure [ Time Frame: 8 weeks ]

Enrollment: 40
Study Start Date: February 2010
Study Completion Date: December 2010
Primary Completion Date: October 2010 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
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

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.


Ages Eligible for Study:   25 Years to 75 Years   (Adult, Senior)
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
  Contacts and Locations
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Please refer to this study by its identifier: NCT01413646

United States, Connecticut
Yale-Griffin Prevention Research Center
Derby, Connecticut, United States, 06418
Sponsors and Collaborators
Griffin Hospital
California Walnut Commission
Principal Investigator: David L. Katz, MD, MPH Yale-Griffin Prevention Research Center
  More Information

Publications automatically indexed to this study by Identifier (NCT Number):
Responsible Party: David Katz, MD, MPH, Yale-Griffin Prevention Research Center Identifier: NCT01413646     History of Changes
Other Study ID Numbers: 2009-15
Study First Received: July 11, 2011
Last Updated: August 9, 2011

Keywords provided by Griffin Hospital:
endothelial function

Additional relevant MeSH terms:
Metabolic Syndrome X
Pathologic Processes
Body Weight
Signs and Symptoms
Insulin Resistance
Glucose Metabolism Disorders
Metabolic Diseases processed this record on April 28, 2017