Original ArticleEffect of nut consumption on oxidative stress and the endothelial function in metabolic syndrome☆
Introduction
Epidemiological studies have consistently demonstrated that frequent nut consumption is associated with reduced risk of developing coronary heart disease (CHD), type 2 diabetes, or death by overall mortality causes.1 It has been claimed that the favourable effects of nuts on the plasma lipoprotein profile is the main mechanism that explains the marked reduced risk of CHD observed in cohort studies.2 However, it has been suggested that other mechanisms of action, such as decreasing inflammation or improving EF, are important for explaining the beneficial effect of nuts on cardiovascular health.
Because of their increasingly recognized healthy benefits, nuts are currently included in several dietary guidelines worldwide and have been proposed as a component of optimal diets for CHD prevention.3, 4
However, nuts are fatty foods and presumably for this reason, until recently, were ignored or treated with a great deal of caution on most dietary recommendations. One of the possible deleterious effects of chronic nut consumption may be because nuts, especially walnuts, very rich in polyunsaturated fatty acids (PUFA).5 Of the various fatty acids, PUFA are the most susceptible to oxidation.6 In fact, a diet enriched with linoleic acid increases LDL oxidation in both human7 and animal experiments.8 This is important because current evidence indicates that oxidative damage plays a key role in atherosclerosis, cancer and other chronic diseases.9
However, emerging evidence indicates that some bioactive compounds in nuts probably counteract the pro-oxidant effect of PUFA on LDL10, 11, 12 and have elicited some cardioprotective effects.6 Several phytochemicals that have been shown to be common in nuts—e.g. polyphenols and phytoesterols—have a variety of bioactions that have been implicated in antioxidant activities. These phytochemicals may work in synergy with other important nut constituents such as antioxidant vitamins (α-tocopherol, γ-tocopherol) and minerals that decrease the oxidative damage to lipids, proteins, and lipoproteins and slow down the progression of the atherosclerosis plaque.13
However, the effect of nut consumption on oxidation has not been well studied. In fact, the effect of nut consumption on oxidative stress has been analyzed in only a few clinical trials, and only in eight was the main outcome related to oxidation. These studies have been conducted in different populations, using different types of nuts, and oxidative damage has been explored using different techniques and approaches, which explains the contradictory results obtained.14 The effect of nut consumption on EF has also been poorly studied and the results are contradictory.12, 15
Therefore, the aim of our study is to evaluate the effect of nut consumption on several steps of the cascade oxidation and endothelial dysfunction in a non diabetic MetS population. The lipid profile, the insulin resistance and the inflammatory responses from this feeding trial have been previously described.16
Section snippets
Subjects
Sixty-one male and female volunteers, aged between 18 and 65 y old with MetS from three Primary Care Centres (Alcover, Riudoms and Reus) of our zone and the University Hospital Sant Joan, Reus (Spain) were screened. To be enrolled the subjects had to have at least three of the following MetS components as defined by the updated Adult Treatment Panel (ATP III) criteria: (a) waist circumference ≥102 cm for men and ≥88 cm for women, (b) triglycerides (TG) ≥1.7 mmol/L or drug treatment for elevated
Results
A total of 61 subjects were assessed for inclusion in the study. Of these, 4 did not meet the inclusion criteria, 4 had severe difficulties in following the study and 1 had started statine therapy just before the randomization. Of the 52 participants randomized, 2 withdrew from the study for personal reasons. A total of 50 subjects (25 in the Control group and 25 in the Nut group) completed the trial and were included in the statistical analyses (Fig. 1). The average age of the 28 men and 22
Discussion
The results of our feeding clinical trial show that, despite the adverse pro-oxidant effect of consuming PUFA in nuts, especially high in walnuts, the consumption of a supplement of 30 g of mixed nuts (walnuts, almonds and hazelnuts) in a context of a healthy diet for 12 wk did not produce a deleterious effect on oxidative stress biomarkers or the endothelial function in MetS patients compared with patients consuming the same healthy diet without nuts. Moreover, DNA damage (measured by the
Conflict of Interest
J. Salas-Salvadó has received research funding from the International Nut Council, Reus, Spain. He is a nonpaid member of the Scientific Advisory Board of the International Nut Council. Mònica Bulló, Patricia Casas-Agustench, Patricia López-Uriarte, Lluís Masana, Rosa Nogués, Marta Romeu, Guillermo Saez and Carmen Tormos, no conflict of interest.
Contribution authors
PLU and JSS wrote the paper; JSS and MB designed the research and had primary responsibility for final content; PLU and PCA conducted research and analyzed data; PLU, PCA, MB, RN, MR, GS and CT conducted experiments of the research. MB, LM, GS, critically reviewed the paper. All authors read and approved the final manuscript.
Acknowledgements
This study was supported by the Spanish Ministry of Education and Science (CICYT-AGL2005-0365), Spanish Ministry of Health (RTIC RD06/0045), and the International Nut Council. Borges S.A. (Reus, Spain) donated the walnuts used in this study. CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN) is an initiative of ISCIII. Patricia López-Uriarte is the recipient of a predoctoral fellowship from the Generalitat de Catalunya's Department of Universities, Research and the Information Society
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Interventions targeted at oxidatively generated modifications of nucleic acids focused on urine and plasma markers
2019, Free Radical Biology and MedicineCitation Excerpt :From the title and abstract of the 6613 identified studies, a total of 232 were selected for full reading. Thirty-five studies [94–128] were identified as having measured 8-oxodG in plasma and 78 studies [11,104,129–204] were identified as having measured 8-oxodG/creatinine in urine; these were selected for comparing the concentrations between analysis procedures. None of the studies used LC-ECD and LC-MS/MS methods for determining 8-oxodG in plasma; thus, we used non-intervention studies as references for the LC-ECD [82,205] and LC-MS/MS methods [206–210].
Effects of nut consumption on selected inflammatory markers: a systematic review and meta-analysis of randomized controlled trials
2018, NutritionCitation Excerpt :Ten studies used a parallel design [17,21,22,34,36,38,44,47,48,50], of which only one was double-blinded [48]. There were seven studies on walnuts [23,33,35,42,43,46,50], four on almonds [32,40–42], five on pistachios [34,39,44,45,49], two on peanuts [37,47], two [36,48], one cashews [50], and four on mixed nuts [17,21,22,38]. The dosages of nut consumption in studies ranged from 28.4 to 128 g/d. Two studies evaluated the effect of two different dosages of nut consumption [36,40] and two other studies assessed the effect of two different types of nuts [42,50].
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