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The bioactive compounds contained in tree nuts have been shown to beneficially affect cardiometabolic health outcomes. Pecans contain more total phenols, sterols, and flavonoids than any other tree nut. They also are a rich source of polyunsaturated fatty acids (PUFAs), fiber, vitamin A, vitamin E, folic acid, calcium, magnesium, phosphorus, potassium, and zinc. These bioactive components in pecans are likely the reason for the previously documented improvements in cardiometabolic health.
The specific aims of this study are to:
Participants will be asked to:
Researchers will compare pecan LOW, pecan MID, pecan HIGH, and the Control group to examine the physiologic effects of incorporating various dosages of pecans into one's diet.
Cardiovascular disease risk factors, including higher BMIs and poor cholesterol profiles, are on the rise and contribute to the United States' growing disease burden. Research investigating the relationship between pecan nut consumption and cardiometabolic outcomes has shown that pecan nut consumption can significantly benefit fasting and postprandial blood lipids, reduce CVD risk factors, promote weight maintenance, improve subjective and psychological markers of physiological appetite, increase total antioxidant capacity, and increase energy expenditure and fat oxidation. However, the current literature on pecan consumption and health outcomes only encompasses physiological benefits coming from a dosage of ~45g/day and above, which is above the current dietary guidelines. This study will be the first dose-response study examining the minimalist effective dose and determining the most effective dosage of pecan consumption on metabolic and cardiovascular outcomes. If lower doses of pecans in the diet are found to improve fasting and postprandial lipid metabolism and markers of chronic disease risk, these study findings could lead to improvements in health.
This prospective clinical study is a single-blinded, randomized control trial in adults at increased risk for cardiovascular disease (poor cholesterol profiles or overweight/obesity). There are four diet interventions: pecan LOW (6% energy from pecans), pecan MID (13% energy from pecans), pecan HIGH (20% energy from pecans), and CON (instructed to maintain their current habitual diet and abstain from any tree nut/peanut consumption for the duration of the intervention). This study protocol consists of a 28-day diet intervention that will involve substituting pecans for commonly consumed snack or meal items every day for the entire 28-day intervention or maintaining a current/usual diet.
There are a total of six testing visits: a screening visit (V0), a pre-intervention visit (V1), short weekly visits (end of weeks 1, 2, and 3; V2-V4), and a post-intervention visit (V5).
At screening (V0), qualification is confirmed based on anthropometrics and fasting blood draw, which is analyzed for a cholesterol panel and blood glucose. Additionally, energy requirements are estimated at this visit for use in the diet intervention.
At V1, participants will have anthropometrics measured, including body composition, by DEXA. Next, a certified phlebotomist places an IV catheter and takes the fasting blood sample. Then the participant consumes a high-saturated-fat meal challenge, delivering 17% of their estimated energy needs (from V0). Then the participant has blood drawn 7 times using the IV catheter over the next 4 hours.
The 28-day diet intervention will consist of research personnel providing pecans that deliver 6%, 13%, or 20% of the participant's daily energy needs (determined at V0). Participants placed in one of the three pecan diets will receive counseling at the baseline (V1) and weekly intervention visits (V2-V4) on substituting pecans for isocaloric foods from their habitual diet. Individuals randomized in the control group will be instructed to follow their habitual diet and will not be provided with any food items.
Participants return weekly (V2, V3, V4) to return study materials and collect food for the next week (if applicable). At these weekly visits, participants also have a fasting blood draw, and researchers will collect the participant's body measurements.
At the end of the 28-day dietary intervention, participants return for V5, where all procedures from V1 are repeated.
The investigators hypothesize that diets including the daily consumption of pecans will benefit health outcomes and lower cardiometabolic risk factors.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Pecan LOW | Experimental | Participants are given pecans and instructed on how to substitute study foods into their diet to maintain caloric balance. |
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| Pecan MID | Experimental | Participants are given pecans and instructed on how to substitute study foods into their diet to maintain caloric balance. |
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| Pecan HIGH | Experimental | Participants are given pecans and instructed on how to substitute study foods into their diet to maintain caloric balance. |
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| CONTROL | Experimental | Participants are asked to maintain their current habitual diet and avoid any tree nut/peanut consumption for the entire 28-day intervention period. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Pecan LOW | Other | Participants are provided with a quantity of pecans that delivers 6% of the participant's estimated energy needs for 28 days. |
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| Measure | Description | Time Frame |
|---|---|---|
| Change in fasting serum lipoprotein and cholesterol concentrations | The concentration of fasting serum total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and apolipoprotein B (mg/dl). | Baseline, 4 weeks |
| Change in fasting serum lipoprotein particle numbers | The number of particles of low-density lipoproteins (LDL), LDL small, HDL large, LDL medium, lipoprotein (a) (nmol/L). | Baseline, 4 weeks |
| Change in fasting and postprandial plasma triglyceride concentrations | The concentration of plasma triglycerides before and after the high saturated fat meal challenge at both pre-and post-intervention visits (mg/dL). | Baseline, 4 weeks |
| Change in fasting and postprandial plasma non-esterified fatty acid (NEFA) concentrations | The concentration of plasma NEFAs before and after the high saturated fat meal challenge at both pre-and post-intervention visits (mEq/L). | Baseline, 4 weeks |
| Change in fasting and postprandial plasma glucose concentrations | The concentration of plasma glucose before and after the high saturated fat meal challenge at both pre-and post-intervention visits (mg/dL). | Baseline, 4 weeks |
| Change in fasting and postprandial plasma insulin concentrations | The concentration of plasma insulin before and after the high saturated fat meal challenge at both pre-and post-intervention visits (uU/mL). | Baseline, 4 weeks |
| Measure | Description | Time Frame |
|---|---|---|
| Change in fasting serum hepatic enzymes | Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), Alkaline phosphatase (ALP), and Gamma-Glutamyl Transferase (GGT) (U/L). | Baseline, 4 weeks |
| Change in fasting serum hepatic proteins |
| Measure | Description | Time Frame |
|---|---|---|
| Change in blood pressure | Systolic and diastolic blood pressure (mmHg). | Baseline, 4 weeks |
| Change in body weight | Body weight (kg). | Baseline, 4 weeks |
Inclusion Criteria:
Exclusion Criteria:
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| Name | Affiliation | Role |
|---|---|---|
| Jamie A Cooper, Ph.D. | University of Georgia | Principal Investigator |
| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| University of Georgia | Athens | Georgia | 30602 | United States |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 41651071 | Derived | Guadagni AJ, Paton CM, Cooper JA. Dose-Response Effects of Pecan Consumption on Blood Lipid Profiles in Adults with Excess Body Weight and/or Dyslipidemia: a Randomized Controlled Trial. J Nutr. 2026 Apr;156(4):101396. doi: 10.1016/j.tjnut.2026.101396. Epub 2026 Feb 4. |
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| ID | Term |
|---|---|
| D050171 | Dyslipidemias |
| D050177 | Overweight |
| D009765 | Obesity |
| ID | Term |
|---|---|
| D052439 | Lipid Metabolism Disorders |
| D008659 | Metabolic Diseases |
| D009750 | Nutritional and Metabolic Diseases |
| D044343 | Overnutrition |
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Four groups of 28-day parallel feeding trials with three groups receiving different amounts of pecans (low, mid, high) and one group serving as control (instructed to maintain their current habitual diet and avoid any nut consumption for the 28-day intervention).
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Participants are blinded to which group they are in and what oil they are receiving.
| Pecan MID | Other | Participants are provided with a quantity of pecans that delivers 13% of the participant's estimated energy needs for 28 days. |
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| Pecan HIGH | Other | Participants are provided with a quantity of pecans that delivers 20% of the participant's estimated energy needs for 28 days. |
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| CONTROL | Other | Participants are asked to maintain their current habitual diet and to avoid any tree nut/peanut consumption for the entire 28-day intervention period. |
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| Change in fasting and postprandial plasma appetite control hormones concentrations | The concentration of plasma appetite control hormones before and after the high saturated fat meal challenge at both pre-and post-intervention visits. Appetite control hormones include Cholecystokinin (CCK), Peptide YY (PYY), and Ghrelin (pg/mL). | Baseline, 4 weeks |
| Change in fasting and postprandial subjective feelings related to appetite | Visual analog scale ratings of feelings related to appetite before and after the high saturated fat meal challenge at both pre-and post-intervention visits. Subjective feelings of hunger, fullness, desire to eat, prospective consumption, and a composite appetite score are measured by visual analog scales (mm). | Baseline, 4 weeks |
| Change in fasting and postprandial plasma Malondialdehyde (MDA) | The concentration of MDA before and after the high saturated fat meal challenge at both pre-and post-intervention visits (nmol/mL). | Baseline, 4 weeks |
| Change in fasting and postprandial plasma total antioxidant capacity | Total antioxidant capacity before and after the high saturated fat meal challenge at both pre-and post-intervention visits (U/mL). | Baseline, 4 weeks |
| Change in fasting and postprandial plasma antioxidant parameters | Glutathione peroxidase activity, superoxide dismutase activity, and glutathione-s-transferase activity before and after the high saturated fat meal challenge at both pre-and post-intervention visits (U/mL). | Baseline, 4 weeks |
| Change in fasting and postprandial plasma inflammatory cytokine concentrations | The concentration of interleukin-1 beta, C reactive protein, tumor necrosis factor-alpha, and interleukin-6 before and after the high saturated fat meal challenge at both pre-and post-intervention visits (pg/mL). | Baseline, 4 weeks |
| Change in fasting and postprandial plasma markers of coagulation potential | The concentration of plasminogen activator inhibitor-1 and tissue factor before and after the high saturated fat meal challenge at both pre-and post-intervention visits (pg/mL). | Baseline, 4 weeks |
| Change in fasting and postprandial plasma angiopoietin-like (ANGPTL) proteins | The concentration of ANGPTL 3, ANGPTL 4, and ANGPTL 8 before and after the high saturated fat meal challenge at both pre-and post-intervention visits (ng/mL). | Baseline, 4 weeks |
| Change in fasting insulin resistance metrics | Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and Homeostatic Model Assessment for β-cell function (HOMA-B) will be calculated from fasting insulin and glucose measures before and after the 28-day intervention. | Baseline, 4 weeks |
Total protein and albumin (g/dL).
| Baseline, 4 weeks |
| Change in fasting serum bilirubin | Total total bilirubin, direct bilirubin, and indirect bilirubin (mg/dL). | Baseline, 4 weeks |
| Change in additional fasting and postprandial plasma inflammatory cytokine concentrations | The concentration of monocyte chemoattractant protein-1 and interleukin-10 before and after the high saturated fat meal challenge at both pre-and post-intervention visits (pg/mL). | Baseline, 4 weeks |
| Change in additional fasting and postprandial plasma markers of coagulation potential | The concentration of Von Willebrand factor, tissue factor pathway inhibitor, fibrinogen, and D-dimer before and after the high saturated fat meal challenge at both pre-and post-intervention visits (pg/mL). | Baseline, 4 weeks |
| Change in overall liking and desire to consume subjective ratings of the intervention food provided | Visual analog scale ratings of feelings related to overall liking and desire to consume the intervention food are measured by visual analog scales (mm). | Baseline, Week 1, Week 2, Week 3, Week 4 |
| Change in acute dietary intake | One-day food logs will be used to record all foods and beverages consumed on testing days. | Baseline, 4 weeks |
| Change in body composition | DEXA will be used to measure body fat percentage (body fat %). | Baseline, 4 weeks |
| Change in diet composition | 3-day food logs will be used to record foods and beverages consumed before and during the 28-day intervention period. | Baseline, Week 2, Week 4 |
| Change in fasting and postprandial fatty acid composition | Fatty acid composition of plasma before and after the high saturated fat meal challenge at pre- and post-intervention visits (% total triglycerides). | Baseline, 4 weeks |
| Change in fasting tocopherol concentrations | Plasma tocopherol concentrations (ug/ml). | Baseline, 4 weeks |
| Change in fasting urolithin concentrations | Plasma urolithin concentrations (ng/mL). | Baseline, 4 weeks |
| Change in anthropometric circumferences | Hip and waist circumferences (cm). | Baseline, 4 weeks |
| Change in resting metabolic rate | Resting metabolic rate (RMR) will be measured for 30 minutes on the TrueOne 2400 (Parvo Medics, Sandy, UT). | Screening |
| Change in perceived stress | A Perceived Stress Scale (PSS) will be administered and scored to determine stress levels. | Baseline, 4 weeks |
| Change in anxiety | The State-Trait Anxiety Inventory (STAI) will be administered and scored to determine anxiety levels. | Baseline, 4 weeks |
| Change in self-reported physical activity levels | The International Physical Activity Questionnaire will be used to collect self-reported average physical activity levels (met/min). | Baseline, Week 2, Week 4 |
| Change in self-reported consumption of the intervention food or foods similar to the intervention food | A 4-week post questionnaire will be used to collect self-reported intake of the intervention food or foods similar to the intervention food. | Baseline, 4 weeks |
| Change in body Mass Index (BMI) | BMI will be calculated based on height and weight measures (kg/m2). | Baseline, 4 weeks |
| Change in self-reported dietary intake | The Diet History Questionnaire III (DHQ III) is an NIH food frequency questionnaire that consists of 135 food and beverage line items and 26 dietary supplement questions. The DHQ III will be used to assess food and dietary supplement intakes prior to participation in the clinical trial. | Screening |
| D009748 | Nutrition Disorders |
| D001835 | Body Weight |
| D012816 | Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |