A Walnut-Enriched Diet Reduces Lipids in Healthy Caucasian Subjects, Independent of Recommended Macronutrient Replacement and Time Point of Consumption: a Prospective, Randomized, Controlled Trial

Charlotte Bamberger, Andreas Rossmeier, Katharina Lechner, Liya Wu, Elisa Waldmann, Renée G Stark, Julia Altenhofer, Kerstin Henze, Klaus G Parhofer, Charlotte Bamberger, Andreas Rossmeier, Katharina Lechner, Liya Wu, Elisa Waldmann, Renée G Stark, Julia Altenhofer, Kerstin Henze, Klaus G Parhofer

Abstract

Studies indicate a positive association between walnut intake and improvements in plasma lipids. We evaluated the effect of an isocaloric replacement of macronutrients with walnuts and the time point of consumption on plasma lipids. We included 194 healthy subjects (134 females, age 63 ± 7 years, BMI 25.1 ± 4.0 kg/m²) in a randomized, controlled, prospective, cross-over study. Following a nut-free run-in period, subjects were randomized to two diet phases (8 weeks each). Ninety-six subjects first followed a walnut-enriched diet (43 g walnuts/day) and then switched to a nut-free diet. Ninety-eight subjects followed the diets in reverse order. Subjects were also randomized to either reduce carbohydrates (n = 62), fat (n = 65), or both (n = 67) during the walnut diet, and instructed to consume walnuts either as a meal or as a snack. The walnut diet resulted in a significant reduction in fasting cholesterol (walnut vs.

Control: -8.5 ± 37.2 vs. -1.1 ± 35.4 mg/dL; p = 0.002), non-HDL cholesterol (-10.3 ± 35.5 vs. -1.4 ± 33.1 mg/dL; p ≤ 0.001), LDL-cholesterol (-7.4 ± 32.4 vs. -1.7 ± 29.7 mg/dL; p = 0.029), triglycerides (-5.0 ± 47.5 vs. 3.7 ± 48.5 mg/dL; p = 0.015) and apoB (-6.7 ± 22.4 vs. -0.5 ± 37.7; p ≤ 0.001), while HDL-cholesterol and lipoprotein (a) did not change significantly. Neither macronutrient replacement nor time point of consumption significantly affected the effect of walnuts on lipids. Thus, 43 g walnuts/d improved the lipid profile independent of the recommended macronutrient replacement and the time point of consumption.

Keywords: carbohydrate; cardiovascular disease; cholesterol; fat; lipids; macronutrient replacement; n-3-PUFA; nuts; walnuts.

Conflict of interest statement

C.B., A.R., K.L., L.W., E.W., R.S., J.A. and K.H. declare no conflict of interest. The research was supported by a grant from the California Walnut Commission (Folsom, CA) to K.G.P.. The Walnut Commission had no role in study performance, data analysis and or manuscript writing.

Figures

Figure 1
Figure 1
Flowchart of study subjects. In total, 204 subjects were randomized. Ten subjects dropped out due to disease (n = 2), medication (n = 1), personal reason (n = 5), protocol violation (n = 2). A total of 194 subjects were included in statistical evaluation. CH: carbohydrate restriction, F: fat restriction, Comb: combined carbohydrate and fat restriction.
Figure 2
Figure 2
Flowchart of study procedures.
Figure 3
Figure 3
Changes in fasting plasma lipid levels and apoB concentrations from baseline (mg/dL) during the walnut diet phase and control diet phase. (n = 194) Values are mean ± SEM. p-value refers to differences between walnut phase and control phase; * p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001. TC, total cholesterol; LDL-C, low density lipoprotein-cholesterol; HDL-C, high density lipoprotein-cholesterol; VLDL-C, very low density lipoprotein-cholesterol; TG, triglycerides; Lp (a), lipoprotein (a); apoB, apolipoproteinB.
Figure 4
Figure 4
Changes in fasting plasma lipid levels and apoB concentration from baseline in subgroups (mg/dL). Values are mean ± SEM. CH: carbohydrates reduced in walnut-phase (n = 62); F: Fat reduced in walnut-phase (n = 65); Comb: both fat and carbohydrates reduced in walnut-phase (n = 67). TC, total cholesterol; LDL-C, low density lipoprotein-cholesterol; HDL-C, high density lipoprotein-cholesterol; VLDL-C, very low density lipoprotein-cholesterol; TG, triglycerides; Lp (a), lipoprotein (a); apoB, apolipoproteinB.
Figure 5
Figure 5
Adherence to recommended macronutrient replacement during walnut consumption. Percentage of daily total calories at baseline, as well as the recommended and the actual distribution of calories, were calculated by analyzing dietary reports.

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