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Research Nut: Hazelnuts

Daily consumption of Oregon hazelnuts affects α-tocopherol status in healthy older adults: A pre-post intervention study.

Michels A.J., S.W. Leonard, S.L. Uesugi, G. Bobe, B. Frei, M.G. Traber, 2018. Daily consumption of Oregon hazelnuts affects α-tocopherol status in healthy older adults: A pre-post intervention study. J Nutr. 2018;148:1924–1930.

Background: Inadequate vitamin E and magnesium intakes are of concern for older adults owing to the associated incidence of age-related diseases. Objective: This study was designed to determine the extent to which a 16-wk intervention with hazelnuts alters vitamin E and magnesium status in a group of older men and women, and used a pre-post intervention design without a control group to adjust for temporal changes. Methods: Participants (n = 32 including 22 women; mean ± SD age: 63 ± 6 y) consumed hazelnuts (∼57 g/d) for 16 wk. Blood and urine samples and anthropomorphic measures were taken at the start and end of the intervention to determine plasma concentrations of α-tocopherol and serum concentrations of magnesium, lipids, glucose, insulin, and high-sensitivity C-reactive protein along with urinary vitamin E metabolites; several other micronutrients were measured by a lymphocyte proliferation assay. There were 3 primary endpoints, calculated as the mean changes in measurements between baseline and the end of the 16-wk intervention for 1) plasma α-tocopherol, 2) urinary α-carboxyethyl hydroxychromanol (α-CEHC; an α-tocopherol metabolite), and 3) serum magnesium. Results: Hazelnut consumption increased concentrations of the urinary α-tocopherol metabolite α-CEHC (mean ± SD: 0.84 ± 0.45 to 1.14 ± 0.50 µmol/g creatinine; P = 0.0006). In addition, hazelnut consumption increased serum concentrations of magnesium (+2.1%, P= 0.05), decreased concentrations of fasting glucose (−3.4%, P = 0.03) and LDL cholesterol (−6.0%, P = 0.02), and decreased total: HDL cholesterol ratios (−4.5%, P = 0.009). No significant changes were observed in blood pressure, lymphocyte proliferation assays, and serum concentrations of insulin, high sensitivity C-reactive protein, triglyceride, α-tocopherol, or HDL cholesterol. Conclusions: Consuming hazelnuts improves a biomarker of vitamin E status in older adults. Vitamin E is a shortfall micronutrient, as identified by the Dietary Guidelines for Americans 2015–2020, which frequently is consumed at levels less than the Estimated Average Requirement of 12 mg/d; thus, hazelnuts should be considered as part of a healthy dietary pattern. This trial was registered at clinicaltrials.gov as NCT03485989.

Effect of nut consumption on semen quality and functionality in healthy men consuming a Western-style diet: a randomized controlled trial.

Salas-Huetos, A., R. Moraleda, S. Giardina, E. Anton, J. Blanco, J. Salas-Salvadó, M. Bulló, 2018. Effect of nut consumption on semen quality and functionality in healthy men consuming a Western-style diet: a randomized controlled trial. Am J Clin Nutr. 108:953–962.

Background: Human semen quality has declined in industrialized countries. Pollution, smoking, and the consumption of a Western style diet are all hypothesized as potential causes. Objective: We evaluated the effect of chronic consumption of nuts on changes in conventional semen parameters and the potential mechanisms implicated. Design: The FERTINUTS study was a 14-wk randomized, controlled, parallel trial. A total of 119 healthy men, aged 18–35 y, were allocated to 1 of 2 intervention groups: one group was fed the usual Western-style diet enriched with 60 g of a mixture of nuts/d (nut group), and the other was fed the usual Western-style diet avoiding nuts (control group). Semen and blood samples were collected at baseline and at the end of the intervention. Dietary information was recorded throughout the trial. Changes in conventional semen parameters (pH, volume, sperm count and concentration, motility, and morphology) were determined as primary outcomes. The effect of nut consumption on sperm DNA fragmentation (SDF), reactive oxygen species (ROS) production, chromosome anomalies (X, Y, and 18), total DNA methylation, and microRNA expression were measured in sperm samples as potential causes of the changes in the seminogram. Results: Compared with the control group, improvements in total sperm count (P = 0.002) and vitality (P = 0.003), total motility (P = 0.006), progressive motility (P = 0.036), and morphology of sperm (P = 0.008) were observed in the nut group. Participants in the nut group showed an increase in the consumption of total fat, monounsaturated fatty acids, polyunsaturated fatty acids, magnesium, vitamin E, α-linolenic acid, total omega-3 (n–3) and ω-3: ω-6 ratio intake during the intervention. Participants in the nut group showed a significant reduction in SDF (P < 0.001) and in the expression of hsa-miR-34b-3p (P = 0.036). No significant changes in ROS, sperm chromosome anomalies, or DNA methylation were observed between groups. Conclusions: The inclusion of nuts in a Western-style diet significantly improves the total sperm count and the vitality, motility, and morphology of the sperm. These findings could be partly explained by a reduction in the sperm DNA fragmentation. This trial was registered at ISRCTN as ISRCTN12857940.

Primary prevention of cardiovascular disease with a Mediterranean diet supplemented with extra-virgin olive oil or nuts.

Estruch, R., E. Ros, J. Salas-Salvadó, M.-I. Covas, D. Corella, F. Arós, E. Gómez-Gracia, V. Ruiz-Gutiérrez, M. Fiol, J. Lapetra, R.M. Lamuela-Raventos, L. Serra-Majem, X. Pintó, J. Basora, M.A. Muñoz, J.V. Sorlí, J.A. Martínez, M. Fitó, A. Gea, M.A. Hernán, M.A. Martínez-González, PREDIMED Study Investigators, 2018. Primary prevention of cardiovascular disease with a Mediterranean diet supplemented with extra-virgin olive oil or nuts. N Engl J Med.  378(25):e34. doi: 10.1056/NEJMoa1800389. Epub 2018 Jun 13.

Background: Observational cohort studies and a secondary prevention trial have shown inverse associations between adherence to the Mediterranean diet and cardiovascular risk. Methods: In a multicenter trial in Spain, we assigned 7447 participants (55 to 80 years of age, 57% women) who were at high cardiovascular risk, but with no cardiovascular disease at enrollment, to one of three diets: a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or a control diet (advice to reduce dietary fat). Participants received quarterly educational sessions and, depending on group assignment, free provision of extra-virgin olive oil, mixed nuts, or small nonfood gifts. The primary end point was a major cardiovascular event (myocardial infarction, stroke, or death from cardiovascular causes). After a median follow-up of 4.8 years, the trial was stopped on the basis of a prespecified interim analysis. In 2013, we reported the results for the primary end point in the Journal. We subsequently identified protocol deviations, including enrollment of household members without randomization, assignment to a study group without randomization of some participants at 1 of 11 study sites, and apparent inconsistent use of randomization tables at another site. We have withdrawn our previously published report and now report revised effect estimates based on analyses that do not rely exclusively on the assumption that all the participants were randomly assigned. Results: A primary end-point event occurred in 288 participants; there were 96 events in the group assigned to a Mediterranean diet with extra-virgin olive oil (3.8%), 83 in the group assigned to a Mediterranean diet with nuts (3.4%), and 109 in the control group (4.4%). In the intention-to-treat analysis including all the participants and adjusting for baseline characteristics and propensity scores, the hazard ratio was 0.69 (95% confidence interval [CI], 0.53 to 0.91) for a Mediterranean diet with extra-virgin olive oil and 0.72 (95% CI, 0.54 to 0.95) for a Mediterranean diet with nuts, as compared with the control diet. Results were similar after the omission of 1588 participants whose study-group assignments were known or suspected to have departed from the protocol. Conclusions: In this study involving persons at high cardiovascular risk, the incidence of major cardiovascular events was lower among those assigned to a Mediterranean diet supplemented with extra-virgin olive oil or nuts than among those assigned to a reduced-fat diet. (Funded by Instituto de Salud Carlos III, Spanish Ministry of Health, and others; Current Controlled Trials number, ISRCTN35739639 .).

Effect of nut consumption on vascular endothelial function: A systematic review and meta-analysis of randomized controlled trials.

Xiao, Y., W. Huang, C. Peng, J. Zhang, C. Wong, J.H. Kim, E.-K. Yeoh, 2017. Effect of nut consumption on vascular endothelial function: A systematic review and meta-analysis of randomized controlled trials. Clinical Nutrition. http://dx.doi.org/10.1016/j.clnu.2017.04.011

Objective: Nut consumption has consistently been found to be associated with a reduced risk of cardiovascular diseases (CVD) and mortality in prospective studies. However, its effect on endothelial function, a prognostic marker of CVD, is still controversial in clinical trials. This meta-analysis of randomized controlled trials (RCTs) aimed to quantitatively assess the effect of nuts on vascular endothelial function. Methods: Major electronic databases were searched for published RCTs that reported the effect of nuts on flow mediated dilation (FMD) as a measurement of endothelial function in the adult population (age eighteen years or over). We calculated the pooled estimates of weighted mean differences (WMDs) and their 95% confidence intervals (CIs) by using random-effects models. Results: A total of nine papers (10 trials) involving 374 participants were included. The pooled estimates found that nut consumption significantly improved FMD (WMD: 0.41%; 95% CI: 0.18%, 0.63%; P = 0.001). Moderate and marginally significant heterogeneity was observed among the studies (I2 = 39.5%, P = 0.094). Subgroup analyses indicated that walnuts significantly improved FMD (WMD: 0.39%; 95% CI: 0.16%, 0.63%; P = 0.001). In addition, nut consumption had a significant effect on FMD in the trials with study duration <18 weeks, nut dose <67 g/d, or subjects with baseline FMD ≥8.6%. Conclusions: Nut consumption significantly improved endothelial function. However, the beneficial effect was limited to walnuts. More studies examining the effect of other nuts on endothelial function are needed in the future.