Acute consumption of walnuts and walnut components differentially affect postprandial lipemia, endothelial function, oxidative stress, and cholesterol efflux in humans with mild hypercholesterolemia

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 × 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.

Trial registration: ClinicalTrials.gov NCT00938340.

Conflict of interest statement

Author disclosures: C. E. Berryman, J. A. Grieger, S. G. West, C-Y. O. Chen, G. H. Rothblat and S. Sankaranarayanan, no conflicts of interest. P.M. Kris-Etherton and J.B. Blumberg are members of the Scientific Advisory Council for the California Walnut Board.

Figures

FIGURE 1

Change in serum concentrations of TG after consumption of each test meal in healthy overweight and obese men and women. Values are least squares means ± SEMs, n = 15. Post hoc analyses at individual time points were conducted using the Bonferroni adjustment for multiple comparisons. *Compared with oil; †compared with whole nut, P < 0.05.

FIGURE 2

Free cholesterol efflux was increased in cells cultured with postmeal serum relative to fasting baseline serum. Values are least squares means ± SEMs, n = 15. *Different from 0 min, P < 0.05.