Acute Effects of High-Fat Meals Enriched With Walnuts or Olive Oil on Postprandial Endothelial Function

Departament de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain.
Journal of the American College of Cardiology (Impact Factor: 16.5). 11/2006; 48(8):1666-71. DOI: 10.1016/j.jacc.2006.06.057
Source: PubMed


We sought to investigate whether the addition of walnuts or olive oil to a fatty meal have differential effects on postprandial vasoactivity, lipoproteins, markers of oxidation and endothelial activation, and plasma asymmetric dimethylarginine (ADMA).
Compared with a Mediterranean diet, a walnut diet has been shown to improve endothelial function in hypercholesterolemic patients. We hypothesized that walnuts would reverse postprandial endothelial dysfunction associated with consumption of a fatty meal.
We randomized in a crossover design 12 healthy subjects and 12 patients with hypercholesterolemia to 2 high-fat meal sequences to which 25 g olive oil or 40 g walnuts had been added. Both test meals contained 80 g fat and 35% saturated fatty acids, and consumption of each meal was separated by 1 week. Venipunctures and ultrasound measurements of brachial artery endothelial function were performed after fasting and 4 h after test meals.
In both study groups, flow-mediated dilation (FMD) was worse after the olive oil meal than after the walnut meal (p = 0.006, time-period interaction). Fasting, but not postprandial, triglyceride concentrations correlated inversely with FMD (r = -0.324; p = 0.024). Flow-independent dilation and plasma ADMA concentrations were unchanged, and the concentration of oxidized low-density lipoproteins decreased (p = 0.051) after either meal. The plasma concentrations of soluble inflammatory cytokines and adhesion molecules decreased (p < 0.01) independently of meal type, except for E-selectin, which decreased more (p = 0.033) after the walnut meal.
Adding walnuts to a high-fat meal acutely improves FMD independently of changes in oxidation, inflammation, or ADMA. Both walnuts and olive oil preserve the protective phenotype of endothelial cells.

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Available from: Emilio Ros, Jan 30, 2014
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    • "Improvements in vascular function have been reported in several dietary interventional trials after walnut intake [1] [4] [6] [7] [10]. Notably, a variety of study designs have been used that include the assessment of vascular function after an overnight fast [7] [10] or during the postprandial period with the walnuts incorporated or consumed with a high-fat meal [3] [4] [11]. The latter studies have explored the potential of walnuts to reduce lipidemia-induced vascular dysfunction , an effect of walnuts that may represent a distinct mechanism of action that is separate from the vascular effects induced during the fasted state [12]. "
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    ABSTRACT: Improved vascular function after the incorporation of walnuts into controlled or high-fat diets has been reported; however, the mechanism(s) underlying this effect of walnuts is(are) poorly defined. The objective of the current study was to evaluate the acute and short-term effects of walnut intake on changes in microvascular function and the relationship of these effects to plasma epoxides, the cytochrome-P450-derived metabolites of fatty acids. Thirty-eight hypercholesterolemic postmenopausal women were randomized to 4 weeks of 5 g or 40 g of daily walnut intake. All outcomes were measured after an overnight fast and 4 h after walnut intake. Microvascular function, assessed as the reactive hyperemia index (RHI), was the primary outcome measure, with serum lipids and plasma epoxides as secondary measures. Compared to 5 g of daily walnut intake, consuming 40 g/d of walnuts for 4 weeks increased the RHI and Framingham RHI. Total cholesterol and low- and high-density cholesterol did not significantly change after walnut intake. The change in RHI after 4 weeks of walnut intake was associated with the change in the sum of plasma epoxides (r=0.65, P=.002) but not with the change in the sum of plasma hydroxyeicosatetraenoic acids. Of the individual plasma epoxides, arachidonic-acid-derived 14(15)-epoxyeicosatrienoic acid was most strongly associated with the change in microvascular function (r=0.72, P<.001). These data support the concept that the intake of walnut-derived fatty acids can favorably affect plasma epoxide production, resulting in improved microvascular function.
    The Journal of nutritional biochemistry 09/2015; DOI:10.1016/j.jnutbio.2015.07.012 · 3.79 Impact Factor
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    • "A sample size of 40 subjects per each of the three centers (120 in total) was determined based on endothelial function as the primary outcome. Endothelial function was intended to be assessed by flow mediated dilatation (FMD) The anticipated difference in means was 20% and the standard deviation was 1.35 [34]. Aforementioned sample size was sufficient to detect this difference with a power of 0.8 at a significance of 0.05. "
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    ABSTRACT: The Canola Oil Multicenter Intervention Trial (COMIT) was a randomized controlled crossover study designed to evaluate the effects of five diets that provided different oils and/or oil blends on cardiovascular disease (CVD) risk factors in individuals with abdominal obesity. The present objective is to report preliminary findings on plasma fatty acid profiles in volunteers with abdominal obesity, following the consumption of diets enriched with n-3, n-6 and n-9 fatty acids. COMIT was conducted at three clinical sites, Winnipeg, Manitoba, Canada, Quebec City, Quebec, Canada and University Park, Pennsylvania, United States. Inclusion criteria were at least one of the followings: waist circumference (>=90 cm for males and >=84 cm for females), and at least one other criterion: triglycerides >=1.7 mmol/L, high density lipoprotein cholesterol <1 mmol/L (males) or <1.3 mmol/L (females), blood pressure >=130 mmHg (systolic) and/or >=85 mmHg (diastolic), and glucose >=5.5 mmol/L. Weight-maintaining diets that included shakes with one of the dietary oil blends were provided during each of the five 30-day dietary phases. Dietary phases were separated by four-week washout periods. Treatment oils were canola oil, high oleic canola oil, high oleic canola oil enriched with docosahexaenoic acid (DHA), flax oil and safflower oil blend, and corn oil and safflower oil blend. A per protocol approach with a mixed model analysis was decided to be appropriate for data analysis. One hundred and seventy volunteers were randomized and 130 completed the study with a dropout rate of 23.5%. The mean plasma total DHA concentrations, which were analyzed among all participants as a measure of adherence, increased by more than 100% in the DHA-enriched phase, compared to other phases, demonstrating excellent dietary adherence. Recruitment and retention strategies were effective in achieving a sufficient number of participants who completed the study protocol to enable sufficient statistical power to resolve small differences in outcome measures. It is expected that the study will generate important data thereby enhancing our understanding of the effects of n-3, n-6, and n-9 fatty acid-containing oils on CVD risks.Trial registration: NCT01351012.
    Trials 04/2014; 15(1):136. DOI:10.1186/1745-6215-15-136 · 1.73 Impact Factor
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    • "On the other hand, studies that tested the postprandial effect of nuts consumed in the context of a meal usually showed antioxidant effects [23,27]. In addition, walnut meals were shown to acutely improve endothelial function [48] and reduce the postprandial inflammatory response in mononuclear cells in humans [24]. "
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    ABSTRACT: In vitro studies rank walnuts (Juglans regia) among the plant foods high in antioxidant capacity, but whether the active constituents of walnuts are bioavailable to humans remains to be determined. The intention of this study was to examine the acute effects of consuming walnuts compared to refined fat on meal induced oxidative stress. At issue is whether the ellagitannins and tocopherols in walnuts are bioavailable and provide postprandial antioxidant protection. A randomized, crossover, and controlled-feeding study was conducted to evaluate a walnut test meal compared to one composed of refined ingredients on postprandial serum antioxidants and biomarkers of oxidative status in healthy adults (n = 16) with at least 1 week between testing sessions. Following consumption of a low phenolic diet for one day and an overnight fast, blood was sampled prior to the test meals and at intervals up to 24 hours post ingestion and analyzed for total phenols, malondiadehyde (MDA), oxidized LDL, ferric reducing antioxidant power (FRAP), hydrophilic and lipophilic oxygen radical absorbance capacity (ORAC), uric acid, catechins and urinary excretion of phenylacetate metabolites and of urolithin A. Mixed linear models demonstrated a diet effect (P < 0.001) for plasma gamma-tocopherol but not for alpha-tocopherol with the walnut meal. Following the walnut test meal, the incremental 5 hour area under the curve (AUC0-5h) was reduced 7.4% for MDA, increased 7.5% for hydrophilic and 8.5% for lipophilic ORAC and comparable for total phenols, FRAP and uric acid. Oxidized LDL was reduced at 2 hours after the walnut meal. Plasma concentrations of gallocatechin gallate (GCG), epicatechin gallate (ECG) and epicallocatechin gallate (EGCG) increased significantly at 1 hour after the walnut test meal. Quantities of urolithin-A excreted in the urine were significantly higher following the walnut meal. Compared to the refined control meal, the walnut meal acutely increased postprandial gamma-tocopherol and catechins and attenuated some measures of oxidative stress.
    Nutrition Journal 01/2014; 13(1):4. DOI:10.1186/1475-2891-13-4 · 2.60 Impact Factor
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