Postprandial Effects of Walnut Components Versus Whole Walnuts on Cardiovascular Disease (CVD) Risk Reduction

Postprandial Effects of Walnut Components vs Whole Walnuts on Oxidative Stress, Inflammation, Platelet Function, and Endothelial Function in Volunteers With Moderate Hypercholesterolemia

The purpose of this study is to evaluate the acute, postprandial effects and mechanism of action of various walnut components (separated nut skins, de-fatted nut meat, nut oil) versus whole walnuts on oxidative stress, inflammation and measures of platelet and endothelial function in healthy adults with moderately elevated cholesterol levels.

Walnuts contain high contents of polyunsaturated fatty acids (PUFA), particularly linoleic acid and linolenic acid. The high PUFA content has been suggested to reduce CVD risk through decreasing total and LDL-cholesterol concentrations, and increasing HDL-C concentrations. In addition, walnuts are rich in substances such as ellagic acid (a polyphenol), antioxidants, vitamin E, fiber, essential fatty acids, flavanoids, and phenolic acids. Polyphenolic compounds are believed to have multiple biological effects influencing oxidative stress, platelet function, inflammation, and cancer initiation and propagation. There is interest in identifying foods with these and other favorable compounds to test their efficacy in real world settings to further understand their role in the human diet. Despite positive benefits found in consumption of the walnuts, it is not known which specific component of the walnut (i.e., whole walnut, walnut skin, defatted walnut, or walnut oil) is most beneficial to health. The investigators hypothesize that maximum improvements in oxidative stress, inflammatory markers, platelet and endothelial function will be observed following consumption of the whole nut versus isolated walnut components, thereby leading to a recommendation to consume walnuts. In addition, results from the research proposed will provide new information about the antioxidant, inflammatory, platelet activity and endothelial effects of the different walnut components and the synergistic effects these components have in the postprandial state.

Inclusion Criteria:

• Age 21 - 60 years
• Body mass index 25-39 kg/m2
• LDL cholesterol >110 mg/dL
• <95 percentile for age and gender for both (based on NHANES data)
• TG < 350 mg/dL

Exclusion Criteria:

• High alcohol consumption > 21 units/week (female subjects) or > 28 units/week (male subjects)
• Intake of vitamin and mineral supplements within the past 3 weeks or unwillingness to discontinue for 3 weeks prior to screening and for entire study.
• Use of prescription cholesterol-lowering or blood pressure-lowering medications during the study
• Intake of other putative cholesterol-lowering supplements (excl. psyllium, fish oil capsules, soy lecithin, phytoestrogens)
• Intake of anti-inflammatory medications (containing aspirin or NSAIDS) on a regular basis or if an acute intake, within 48 hours of a test day
• Diabetes, liver, kidney, thyroid (unless controlled and stable on replacement medication) or other endocrine disorders from self-reported medical history
• Treatment with drugs acting on the gut, such as ezetimibe, bile acid-binding resins, orlistat
• Dietary restrictions such as a medically prescribed diet, or a slimming diet prior to or during the trial
• Weight loss or gain of 10% body weight or more during a period of 6 months before pre-study examination.
• Blood/plasma donation for reason(s) other than the present study prior to the study (1 month for a male subject or 2 months for a female subject), or during the study
• Lactation 6 weeks before the start of and during study, pregnant or wishing to become pregnant 3 months before or during the study