Cardiometabolic Effects of the Recommended Daily Pecan Intake Dose

Accounting for nearly 1 in every 4 deaths in the U.S., cardiovascular disease (CVD) is the leading cause of death for adults. One risk factor for CVD is hypercholesterolemia, which can double the risk for this disease. 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. Recent evidence from our pecan dose-response study showed that consuming 6% of energy needs from pecans (~ 21.5 g/day) trended toward reductions in blood lipids but did not reach significance by the end of the short, 4-week intervention. Based on previous interventions with low doses of tree nuts, a longer duration, such as 12 weeks, may be needed to see significant effects. 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 and possibly provide additional information about dietary guidelines for nut consumption.

This prospective clinical study is a single-blinded, randomized control trial in adults at increased risk for cardiovascular disease (poor cholesterol profiles and/or overweight/obesity). There are two diet interventions: Pecan (6% of energy needs from pecans) and Control (instructed to maintain their current habitual diet, but abstain from any tree nut/peanut consumption and limit nut butters to no more than 2x/wk during the intervention). The study protocol consists of a 12-week intervention that will involve substituting pecans for commonly consumed snack or meal items every day for the entire 12-week intervention or maintaining a current/usual diet.

There are a total of 5 testing visits: screening (v0), pre-intervention (v1), 2 short visits at 4 and 8 weeks (v2, v3), and post-intervention (v4).

At screening (v0), qualification is confirmed based on anthropometrics and a 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 dual-energy x-ray absorptiometry (DXA). Fasting and postprandial blood draws for a 4h period will occur following a high saturated-fat meal challenge which delivers 17% of the participant's estimated energy needs.

12-week dietary intervention: The 12-week diet intervention will consist of research personnel providing pecans that deliver 6% of the participant's daily energy needs (determined at V0). Participants randomized in the pecan group will receive dietary counseling at the baseline (V1) and intervention visits at 4 and 8 weeks (V2-V3) on substituting pecans for isocaloric foods from their habitual diet. Individuals randomized in the control group will be instructed to follow their habitual diet, but avoid any tree nut/peanut consumption and limit nut butter to no more than 2x/wk, and will not be provided with any food items.

Participants return at 4 and 8 weeks (v2, v3) to return study materials and collect pecans for the next four weeks (if applicable). At these mid-intervention visits, participants also have a fasting blood draw and body measures taken.

At the end of the 12-week dietary intervention, participants return for v4, where all procedures from v1 are repeated.

As decided a priori, we will complete a per protocol analysis. The investigators hypothesize that including the daily consumption of pecans will improve the proposed overall health outcomes and markers of chronic disease risk compared to the control group.

Inclusion criteria

• 25-75 year-old men and women at increased risk for cardiovascular disease. Increased risk for cardiovascular disease will be defined by either elevated cholesterol profiles -or- overweight/obesity.
• Elevated cholesterol profiles will be defined as:
• "Borderline High" and/or "at risk" in two or more of the following variables (total cholesterol: 180-239 mg/dL, LDL cholesterol 110-159 mg/dL, triglycerides 130-199 mg/dL) --or-- "High" in total cholesterol (240 mg/dL and higher), LDL (160 mg/dL or higher), or triglycerides (between 200-350 mg/dL).
• Overweight/obesity will be defined by body mass index (overweight > 28 kg/m2 or obesity 30 kg/m2 or greater).

Exclusion criteria

• Probable familial hypercholesterolemia, defined by: total cholesterol greater than 290 mg/dL or LDL levels greater than 190 mg/dL plus a family history of myocardial infarction (MI) before 50 years of age in a 2nd-degree relative or below age 60 in a 1st-degree relative.
• Women on hormone replacement therapy less than 2 years.
• Women who are pregnant or nursing
• Individuals who regularly exercise more than 3h/w
• Weight gain or loss of more than 5% body weight in the past 3 months
• Plans to begin a weight loss/exercise regimen during the trial
• History of medical or surgical events that could affect digestion or swallowing
• Gastrointestinal surgeries, conditions, or disorders
• Any chronic diseases (including moderate to severe asthma, chronic lung disease, and kidney disease)
• Metabolic disease
• Atherosclerosis
• Previous MI or stroke
• Cancer
• Fasting blood glucose levels greater than 126 mg/dL
• Blood pressure greater than 180/120 mmHg
• Medication use affecting digestion, absorption, or metabolism (e.g. thyroid meds), lipid-lowering medications, medications for diabetes, steroid/hormone therapies, or current antibiotic cycles
• Medically prescribed or special diets
• Food allergies (specific to the foods in the study, including tree nuts, dairy, gluten, palm oil, and coconut oil)
• Fish oil supplements
• Individuals who regularly consume nuts and/or nut butter (defined as consumption of >2 servings (~56g) of tree nuts, nuts, or nut butter (e.g., peanut butter, almond butter) per week
• Excessive alcohol use (greater than 3 drinks/day for men; greater than 2 drinks/day for women)
• Tobacco or nicotine use
• Underweight BMI (<18.5 kg/m²)