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United States Department of Agriculture

Agricultural Research Service

Research Project: PHYTOCHEMICALS AND AGING: BIOAVAILABILITY, METABOLOMICS, AND BIOACTIVITY

Location: Human Nutrition Research Center on Aging

Title: Acute Consumption of Walnuts and Walnut Components Differentially Affect Postprandial Lipemia, Endothelial Function, Oxidative Stress, and Cholesterol Efflux in Humans with Mild Hypercholesterolemia.

Authors
item Berryman, Claire -
item Grieger, Jessica -
item West, Selia -
item Chen, C-Y Oliver -
item Blumberg, Jeffrey -
item Rothblat, George -
item Sankaranarayanan, Sandyha -
item Kris-Etherton, Penny -

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 18, 2013
Publication Date: June 1, 2013
Citation: Berryman, C.E., Grieger, J.A., West, S.G., Chen, C., Blumberg, J.B., Rothblat, G.H., Sankaranarayanan, S., Kris-Etherton, P.M. 2013. Acute Consumption of Walnuts and Walnut Components Differentially Affect Postprandial Lipemia, Endothelial Function, Oxidative Stress, and Cholesterol Efflux in Humans with Mild Hypercholesterolemia.. Journal of Nutrition. 143:788-794.

Interpretive Summary: Cardiovascular disease continues to be the leading cause of morbidity and mortality in the United States. This has been the impetus for implementing new strategies to reduce the public health burden of cardiovascular disease. Walnuts are found to be protective against cardiovascular disease, mediated by their constituent polyphenols, vitamin E, omega-3 fatty acid, and arginine. Regular consumption of walnuts (42.5-85 g/day) lowers blood cholesterol, decreases blood pressure, improves blood vessel function, may have beneficial effects on fighting free radicals while reducing inflammation. However, the contribution of individual walnut components has not been assessed. This study evaluated the regular consumption of whole walnuts (85 g), separated nut skins (5.6 g), de-fatted nutmeat (34 g), and nut oil (51 g) on post-meal levels of fats, blood vessel function, and antioxidant defense in healthy overweight and obese adults. We found that regular consumption of walnut oil favorably affects blood vessel function compared to whole walnuts and walnut skins. We also demonstrated novel effects of whole walnuts on cholesterol metabolism. Therefore, frequent consumption of walnuts and/or walnut oil (which typically is how walnut products are consumed) may improve cardiovascular risk via mechanisms that extend beyond their established cholesterol-lowering action.

Technical Abstract: Walnut consumption improves cardiovascular disease risk; however, to our knowledge, the contribution of individual walnut components has not been assessed. This study evaluated the acute consumption of whole walnuts (85 g), separated nut skins (5.6 g), de-fatted nutmeat (34 g), and nut oil (51 g) on postprandial lipemia, endothelial function, and oxidative stress. Cholesterol efflux (ex vivo) was assessed in the whole walnut treatment only. A randomized, 4-period, crossover trial was conducted in healthy overweight and obese adults (n = 15) with moderate hypercholesterolemia. There was a treatment 3 time point interaction for triglycerides (P < 0.01) and increased postprandial concentrations were observed for the oil and whole walnut treatments (P < 0.01). Walnut skins decreased the reactive hyperemia index (RHI) compared with baseline (P = 0.02) such that a difference persisted between the skin and oil treatments (P = 0.01). The Framingham RHI was maintained with the oil treatment compared with the skins and whole nut (P < 0.05). There was a treatment effect for the ferric reducing antioxidant potential (FRAP) (P < 0.01), and mean FRAP was greater with the oil and skin treatments compared with the nutmeat (P < 0.01). Cholesterol efflux increased by 3.3% following whole walnut consumption in J774 cells cultured with postprandial serum compared with fasting baseline (P = 0.02). Walnut oil favorably affected endothelial function and whole walnuts increased cholesterol efflux. These 2 novel mechanisms may explain in part the cardiovascular benefits of walnuts.

Last Modified: 7/25/2014
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