Cardiometabolic Effects of Pecans as a Snack: A Randomized Controlled Trial
Restricted (Penn State Only)
- Author:
- Hart, Tricia
- Graduate Program:
- Nutritional Sciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 04, 2024
- Committee Members:
- Meg Bruening, Program Head/Chair
Gregory Shearer, Major Field Member
Michael Russell, Outside Unit & Field Member
Alison Gernand, Major Field Member
Kristina Petersen, Chair & Dissertation Advisor - Keywords:
- cardiometabolic diseases
metabolic syndrome
tree nuts
pecans
lipids
lipoproteins
flow mediated dilation
HEI-2020 - Abstract:
- Tree nut intake benefits cardiometabolic health, but polyphenol-rich pecans have been less studied. The aim of this dissertation was to evaluate the cardiometabolic effects of consuming pecans in place of usual snacks compared to usual intake in adults at risk for cardiometabolic diseases. This was a 12-week parallel randomized controlled trial in which generally healthy adults with overweight or obesity and ≥1 feature of metabolic syndrome were instructed to 1) replace usual snacks with 57 g/day (2 oz) of raw, unsalted pecans or 2) continue consuming their usual diet. The primary outcome was flow mediated dilation (FMD). Secondary outcomes included diet quality, measures of arterial stiffness (i.e., pulse wave velocity, augmentation index), central and peripheral blood pressure, lipids, lipoproteins, lipoprotein subfractions, markers of glycemic control, (i.e., insulin, glucose, hemoglobin A1C), markers of systemic inflammation (i.e., C-reactive protein), and weight. Exploratory outcomes included early markers of insulin resistance (i.e., Lipoprotein Insulin Resistance Score, Diabetes Risk Index, GlycA). All vascular and cardiometabolic outcomes were measured at baseline and after 12 weeks. Dietary intake was assessed by three self-administered 24-hour recalls conducted at three time points during the study (baseline, week 6, and week 12) resulting in a total of 9 recalls during the trial. Diet quality was assessed using the Healthy Eating Index-2020 (HEI-2020). Nutrient displacement was examined to evaluate how instructions to replace usual snacks affected nutrient intake. Of the 138 participants enrolled, 130 adults completed the trial (pecan group n=62, usual diet group n=68). Baseline characteristics were similar between the groups. Overall, participants had an average age of 46 ± 13 years and a BMI of 29.8 ± 3.7 kg/m2. No between-group differences in the change from baseline for FMD or vascular measures, body weight, and systemic inflammation were observed. Pecan intake reduced total cholesterol (-8.1 mg/dL; 95% CI -14.5, -1.7), low-density lipoprotein cholesterol (-7.2 mg/dL; 95% CI -12.3, -2.1), non-high density lipoprotein cholesterol (-9.5 mg/dL; 95 %CI -15.3, -3.7), triglycerides (-16.4 mg/dL; 95% CI -30.0, -2.9), and apolipoprotein B (-4.38 mg/dL; 95% CI -8.02, -0.73). Atherogenic lipoprotein subfractions and the Lipoprotein Insulin Resistance Score were also improved with pecan intake compared to the usual diet group. The HEI-2020 was increased by 9.4 points (95% CI 5.0, 13.7) in the pecan group compared to the usual diet group. This result was driven by increases in the scores for total protein foods, seafood and plant proteins, fatty acids, and added sugar in the pecan group compared to the usual diet group after 12 weeks. At week 12, partial nutrient displacement occurred for energy (84%; 331 ± 47.8 kcal), total fat (55%; 22.6 ± 0.50 g), monounsaturated fat (MUFA) (47%; 10.9 ± 0.23 g), polyunsaturated fat (PUFA) (46%; 5.71 ± 0.07 g), and fiber (60%; 3.29 ± 0.03 g) in the pecan group. Full nutrient displacement occurred for saturated fatty acids 3.5 ± 0.0 g (100%) and nutrient displacement >100% occurred of carbohydrates (343%; 27.1 ± 0.12 g) and protein (220%; 11.4 ± 0.04) at 12 weeks. In adults at increased risk for cardiometabolic diseases, consumption of 57 g/day of pecans in place of usual snacks did not affect FMD, but reduced atherogenic lipids/lipoproteins. The pecan group increased adherence to the 2020-2025 Dietary Guidelines for Americans supported by an increase in the total HEI-2020, which was driven by improvements in total protein foods, seafood and plant proteins, fatty acids, and added sugars. Incorporating pecans into the diet caused partial nutrient displacement for energy, total fat, MUFA and PUFA and nutrient displacement >100% for carbohydrates and proteins. Consuming pecans in place of usual snacks is an effective food-based recommendation to reduce atherogenic lipids/lipoproteins and improve diet quality in individuals at risk for cardiometabolic diseases.