Walnut Ingestion in Adults at Risk for Diabetes: Effects on Body Composition, Diet Quality, and Cardiac Risk Measures

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

NA

Total Enrollment

112 participants

Study Classification

INTERVENTIONAL

Study Start Date

2012-02-29

Study Completion Date

2014-04-30

Brief Summary

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Proposed is a randomized, controlled, modified Latin square parallel design study with two treatment arms to examine walnut consumption effects on diet quality, body composition, and markers of cardiovascular risk in adults at risk for diabetes over a 6-month period. A modified crossover design (Latin square)27-29 will allow for both paired and unpaired analyses.

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Detailed Description

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Specific Aims

* To determine the effects of a walnut-included diet (with or without caloric intake adjustment) versus walnut-excluded diet on diet quality in adults at risk for diabetes. Specifically, to show that a walnut-included diet, as compared to a walnut-excluded diet will improve overall diet quality as measured by the Alternative Healthy Eating Index in adults at risk for diabetes.
* To determine the effects of a walnut-included diet (with or without caloric intake adjustment) versus walnut-excluded diet on body composition in adults at risk for diabetes. Specifically, to show that a walnut-included diet, as compared to a walnut-excluded diet for 6 months will improve body fat percentage in adults at risk for diabetes.
* To assess the effects of a walnut-included diet (with or without caloric intake adjustment) for a 6-month period on endothelial function, lipid panel levels, fasting glucose level, fasting insulin level and anthropometric measures in adults at risk for diabetes. Specifically, to show clinically meaningful improvement in endothelial function, lipid panel, fasting blood glucose, hemoglobin A1c (HbA1c), anthropometric measures and endothelial function with inclusion of walnuts in the diet in adults at risk for diabetes.

Hypotheses

* A walnut-included diet with or without dietary counseling to adjust caloric intake will improve diet quality in adults at risk for diabetes.
* A walnut-included diet for 6 months with or without dietary counseling to adjust caloric intake will improve body composition in adults at risk for diabetes.
* A walnut-included diet with or without dietary counseling to adjust caloric intake will improve lipid panel, fasting blood glucose, hemoglobin A1c, endothelial function and anthropometric measures in adults at risk for diabetes.
* Controlling calorie intake to keep it constant with the addition of walnuts to the diet will enhance the beneficial effects of walnut ingestion on diet quality, body composition, and vascular function.

Conditions

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Diabetes

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

CROSSOVER

Primary Study Purpose

PREVENTION

Blinding Strategy

SINGLE

Investigators

Study Groups

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Walnut Ad libitum diet

Participants will be provided 392 grams of walnuts per week (56g or 2 oz/day) to include in their diet. Their calorie intake will not be subsequently monitored or regulated, and thus will be allowed to float ad libitum.

Group Type ACTIVE_COMPARATOR

Walnut Ad libitum diet

Intervention Type DIETARY_SUPPLEMENT

Participants will be provided 392 grams of walnuts per week (56g or 2 oz/day) to include in their diet. Their calorie intake will not be subsequently monitored or regulated, and thus will be allowed to float ad libitum

Walnut Calorie Controlled

The intervention group participants will meet with a registered dietitian and receive instructions and recipes for inclusion of 392 grams of walnuts per week (56g or 2 oz/day) in their meal plan. Participants will receive on-going instruction to preserve an isocaloric condition after the addition of walnuts. The study dietitian will customize dietary adjustments to make room for walnuts in the diet, while accommodating the priorities of each study participant. The general approach will emphasize general reduction in portion sizes; participants will also receive advice, based on baseline dietary intake analysis, of food eliminations that they might want to consider.

Group Type ACTIVE_COMPARATOR

Walnut Calorie controlled

Intervention Type DIETARY_SUPPLEMENT

The intervention group participants will meet with a registered dietitian and receive instructions and recipes for inclusion of 392 grams of walnuts per week (56g or 2 oz/day) in their meal plan for 6 months.

Interventions

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Walnut Ad libitum diet

Participants will be provided 392 grams of walnuts per week (56g or 2 oz/day) to include in their diet. Their calorie intake will not be subsequently monitored or regulated, and thus will be allowed to float ad libitum

Intervention Type DIETARY_SUPPLEMENT

Walnut Calorie controlled

The intervention group participants will meet with a registered dietitian and receive instructions and recipes for inclusion of 392 grams of walnuts per week (56g or 2 oz/day) in their meal plan for 6 months.

Intervention Type DIETARY_SUPPLEMENT

Eligibility Criteria

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Inclusion Criteria

* Male and female age 25-75 years;
* Non-smoker;
* High risk for diabetes, defined as meeting at least one of the criteria listed below:

a. Overweight with increased waist circumference; b.Pre-diabetes: fasting blood glucose \>100mg/dL and \<126mg/dL or HbA1C 5.7-6.4 % c. Metabolic syndrome, i.e. meet three out of five of the following criteria: i.Blood pressure \>130/85 mmHg or currently taking antihypertensive medication; ii. Fasting plasma glucose (FPG) \>100 mg/dL (6.1 mmol/L); iii.Serum triglycerides level (TG)\>150 mg/dL (1.69 mmol/L); iv. High-density lipoprotein (HDL) cholesterol \< 40 mg/dL (1.04 mmol/L) in men, and \< 50 mg/dL (1.29 mmol/L) in women; v. Overweight (BMI ≥25kg/m²) with waist circumference of more than 40 inches (102 cm) for men and more than 35 inches (88 cm) for women.

Exclusion Criteria

* Allergy to walnuts or any other nuts;
* Anticipated inability to complete study protocol for any reason;
* Current eating disorder;
* Restricted diets by choice (i.e., vegetarian, vegan);
* Receiving pharmacotherapy for obesity, including appetite suppressant
* Unstable use of lipid-lowering, antihypertensive medications or aspirin (i.e. dose has changed in the three months prior to enrollment) or unwilling to refrain from taking medication for 12 hours prior to endothelial function scanning;
* Regular use of high doses of vitamin E (\>400IU/day) or vitamin C (\>500mg/day); fish oil, flaxseed oil, omega-3 fatty acid and fiber supplement unless welling to discontinue supplementation for the study duration.
* Use of insulin, glucose-sensitizing medication, vasoactive medication (including glucocorticoids, antineoplastic agents, psychoactive agents, or bronchodilators);
* Diagnosed diabetes;
* Diagnosed sleep apnea;
* Established cardiovascular disease (including symptomatic coronary artery disease (CAD), myocardial infarction, peripheral vascular disease, congestive heart failure, carotid stenosis);
* Coagulopathy, known bleeding diathesis, or history of clinically significant hemorrhage; current use of warfarin;
* Regular exercise defined as participation in moderate-intensity exercise \> 150 minutes/week.
* 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)
* Women who get Depo-Provera shots
* Women who are pregnant or lactating
* Women who are currently on hormone replacement therapy
* 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)

Minimum Eligible Age

25 Years

Maximum Eligible Age

75 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

No