Cardiometabolic Effects of Pecan Snacking in Prediabetes

Glycemic Effects of Substituting Pecans for Snacks Higher in Saturated Fat and Added Sugars in Individuals With Prediabetes

The purpose of this study is to investigate the effects of replacing snacks higher in saturated fats and added sugars with pecans on blood sugar control, heart health and diet quality in individuals with prediabetes. Participants will be randomized into one of two groups. Group 1 will consume 1.5 oz of pecans per day in place of normally consumed snacks higher in saturated fat and added sugars for 16 weeks. Group 2 will be asked to continue consuming their current diet for 16 weeks. Measures will be taken to evaluate blood sugar, heart health and dietary intake at the beginning and 16 weeks later.

Study Overview

• Status: Recruiting
• Conditions: Prediabetes
• Intervention / Treatment: Behavioral: Pecan snacking; Other: Usual diet

Detailed Description

This is a 16-week randomized controlled trial. Participants will be randomized to either: 1) replace current snacks higher in saturated fat and added sugars with 1.5 oz/day of pecans; 2) continue their habitual diet. At the beginning and the end of the 16-week study period, testing will be conducted.

• Study Type: Interventional
• Enrollment (Estimated): 147
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Kristina Petersen, PhD; Phone Number: 814-865-7206; Email: kup63@psu.edu
• Study Contact Backup: Name: Stacey Meily; Phone Number: 814-863-8622; Email: sas117@psu.edu

Study Locations

• United States
  • Pennsylvania
    • University Park, Pennsylvania, United States, 16802
      • Recruiting
      • The Pennsylvania State University
      • Contact: Kristina Petersen, PhD; Phone Number: 814-865-7206; Email: kup63@psu.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Age 25-65 years
• Prediabetes assessed by an HbA1c of 5.7-6.4% at screening
• BMI 25-40 kg/m2 at screening
• Low habitual nut consumption (<3.5 oz-eq/week) assessed at the telephone screening
• Regularly eats snacks higher in saturated fat and/or added sugars assessed at the telephone screening

Exclusion Criteria:

• LDL-C ≥190 mg/dL at screening
• Hemoglobin <13.2 g/dL at screening
• Fasting triglycerides >350 mg/dL at screening
• ≥10% change in body weight within the 6 months prior to enrollment
• Blood pressure >140/90 mmHg at screening
• Type 1 or type 2 diabetes
• Prescription of anti-hypertensive, lipid-lowering, or glucose-lowering drugs
• Intake of supplements or over-the-counter medications that affect the outcomes of interest (i.e., lipid, blood pressure, or glucose lowering; vitamin C or multi-vitamins containing vitamin C) and are unwilling to cease during the study period.
• History of liver, kidney, or autoimmune disease
• Prior cardiovascular event (e.g., stroke, heart attack)
• Current pregnancy or intention of pregnancy within the next 12 months
• Lactation within the prior 6 months
• Pecan allergy/intolerance/sensitivity/dislike
• Unwilling/unable to eat 1.5 oz of pecans every day as a snack during the duration of the study
• Antibiotic use within the prior 4 weeks
• Oral steroid use within the prior 4 weeks
• Use of tobacco or nicotine-containing products within the past 6 months
• History of cancer at any site within the past 10 years (eligible if ≥10 years without recurrence) or non-melanoma skin cancer within the past 5 years (eligible if ≥5 years without recurrence)
• Participation in another clinical trial within 60 days of baseline
• Unwilling to contact study staff before enrolling in other health-related research and avoid participating in any research that may interfere with this study.
• Currently following a restricted or weight-loss diet
• Prior bariatric surgery
• Intake of >14 alcoholic drinks/week and/or not willing to avoid alcohol consumption for 48 hours prior to test visits
• Principal Investigator discretion related to the potential participant's ability to adhere to the study requirements, including being able to come to attend visits
• Does not speak and/or understand English
• Unwilling to refrain from donating blood or plasma during the study
• Weight <110 lb
• If a potential participant takes thyroid medicine, abnormal thyroid stimulated hormone (TSH) concentration (TSH outside of normal range), or change in dose of thyroid medication within the last 6 months

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Pecan snacking group; Participants will be provided with 1.5 oz/day of pecans and asked to eat these instead of typically consumed snacks higher in saturated fat and added sugars.	Behavioral: Pecan snacking; Replacement of typically consumed snacks with 1.5 oz/day of pecans
Active Comparator: Usual diet; Participants will be asked to continue consuming their usual diet. To match attention and resources, participants will be provided with a grocery voucher in approximately equivalent value to the pecans.	Other: Usual diet; Continue with usual diet

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in HbA1c	HbA1c will be assessed at baseline and 16-weeks and expressed as percentage . The change in HbA1c will be calculated by subtracting the baseline value from the 16 week value and expressed as percentage point change.	16 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in fasting glucose	Change in fasting plasma glucose expressed as mg/dL. Change in glucose will be calculated as the mean of the 16 week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).	16 weeks
Change in mean glucose	Change in mean glucose assessed by a continuous glucose monitor (CGM) expressed as mg/dL. Change in mean glucose will be calculated as mean glucose assessed from 7 days of CGM wear at 16 weeks minus mean glucose assessed from 7 days of CGM wear at baseline.	16 weeks
Change in mean time in range	Change in mean time in range (glucose 70-140 mg/dL) assessed by a continuous glucose monitor (CGM) expressed as minutes per day. Change in mean time in range will be calculated as mean time in range assessed from 7 days of CGM wear at 16 weeks minus mean time in range assessed from 7 days of CGM wear at baseline.	16 weeks
Change in glycemic variability	Change in mean glycemic variability assessed by a continuous glucose monitor (CGM) expressed as the coefficient of variability. Change in mean glycemic variability will be calculated as mean glycemic variability assessed from 7 days of CGM wear at 16 weeks minus mean glycemic variability assessed from 7 days of CGM wear at baseline.	16 weeks
Change in fasting insulin	Change in fasting serum insulin expressed as micro IU/mL. Change in insulin will be calculated as the mean of the 16 week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).	16 weeks
Change in homeostatic model of insulin resistance (HOMA-IR)	Homeostatic model of insulin resistance (HOMA-IR) will be calculated from insulin and glucose measured from a fasting blood sample. Calculated as (insulin × glucose) / 22.5. Change in HOMA-IR will be calculated as the mean of the 16 week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).	16 weeks
Change in the lipoprotein insulin resistance index	The lipoprotein insulin resistance index will be calculated from Nuclear Magnetic Resonance assessed lipoprotein concentrations according to a previously described method: Metab, Syndr. Relat. Disord. 12 (8) (2014) 422-429. Change will be calculated by subtracting the baseline value from the 16 week value.	16 weeks
Change in LDL-Cholesterol	Assessed from fasting blood draw expressed in mg/dL. Change in LDL-cholesterol will be calculated as the mean of the 16-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).	16 weeks
Change in apolipoprotein B	Assessed from fasting blood draw expressed in mg/dL. Change in apolipoprotein B will be calculated by subtracting the baseline value from the 16 week value.	16 weeks
Change in non-HDL cholesterol	Assessed from fasting blood draw expressed in mg/dL. Change in non-HDL cholesterol will be calculated as the mean of the 16-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).	16 weeks
Change in Total Cholesterol	Assessed from fasting blood draw expressed in mg/dL. Change in total cholesterol will be calculated as the mean of the 16-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).	16 weeks
Change in HDL-Cholesterol	Assessed from fasting blood draw expressed in mg/dL. Change in HDL-cholesterol will be calculated as the mean of the 16-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).	16 weeks
Change in Triglycerides	Assessed from fasting blood draw expressed in mg/dL. Change in triglycerides will be calculated as the mean of the 16-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).	16 weeks
Change in C-reactive protein	Assessed from fasting blood draw expressed in mg/L. Change in C-reactive protein will be calculated as the mean of the 16-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).	16 weeks
Change in Central Systolic and Diastolic Blood Pressure	Central blood pressure measured assessed using a SphymoCor Xcel (Atcor Medical) at baseline & 16 weeks. Change will be calculated by subtracting the baseline value from the end point value.	16 weeks
Change in Peripheral Systolic and Diastolic Blood Pressure	Peripheral blood pressure measured assessed using a SphymoCor Xcel (Atcor Medical) at baseline & 16 weeks. Change will be calculated by subtracting the baseline value from the end point value.	16 weeks
Change in Carotid-Femoral Pulse Wave Velocity	Measured assessed using a SphymoCor Xcel (Atcor Medical) at baseline & 16 weeks. Change will be calculated by subtracting the baseline value from the end point value.	16 weeks
Change in particle size and number of LDL, HDL, triglyceride rich lipoproteins	Measured via Nuclear Magnetic Resonance at baseline and 16 weeks. The change will be calculated by subtracting the baseline value from the 16 week value.	16 weeks
Change in Saturated fat intake	Assessed from 24-hour recalls completed prior to baseline and at 16 weeks. Change in saturated fat will be calculated as saturated fat intake at 16 weeks minus baseline saturated fat intake.	16 weeks
Change in added sugar intake	Assessed from 24-hour recalls completed prior to baseline and at 16 weeks. Change in added sugar intake will be calculated as added sugar intake at 16 weeks minus baseline added sugar intake.	16 weeks
Change in diet quality	Assessed from 24-hour recalls completed prior to baseline and at 16 weeks. Diet quality will be calculated according to the Healthy Eating Index-2020 (HEI). Change in HEI will be calculated as HEI at 16 weeks minus baseline HEI.	16 weeks

Collaborators and Investigators

• Sponsor: Penn State University
• Collaborators: American Pecan Promotion Board

Study record dates

Study Major Dates

• Study Start (Actual): May 22, 2026
• Primary Completion (Estimated): September 30, 2027
• Study Completion (Estimated): September 30, 2027

Study Registration Dates

• First Submitted: November 14, 2025
• First Submitted That Met QC Criteria: November 14, 2025
• First Posted (Actual): November 19, 2025

Study Record Updates

• Last Update Posted (Actual): May 27, 2026
• Last Update Submitted That Met QC Criteria: May 22, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: nutrition; cardiovascular disease; diet; prediabetes; nuts; snacking
• Additional Relevant MeSH Terms: Endocrine System Diseases; Metabolic Diseases; Glucose Metabolism Disorders; Diabetes Mellitus; Nutritional and Metabolic Diseases; Cardiovascular Diseases; Prediabetic State
• Other Study ID Numbers: PEC

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified individual participant data will be deposited into an open access repository once results from all pre-specified primary and secondary outcomes are published.
• IPD Sharing Time Frame: The SAP and protocol will be posted on clinicaltrials.gov prior to enrollment commencing.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No