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Research Nut: Hazelnuts

Effects of hazelnut consumption on blood lipids and body weight: A systematic review and Bayesian meta-analysis.

S. Perna, A. Giacosa, G. Bonitta, C. Bologna, A. Isu, D. Guido, M. Rondanelli, 2016. Effects of hazelnut consumption on blood lipids and body weight: A systematic review and Bayesian meta-analysis. Nutrients. 8,747; doi:10.3390/nu8120747.

Hazelnuts are rich in monounsaturated fatty acids and antioxidant bioactive substances: their consumption has been associated with a decreased risk of cardiovascular disease events. A systematic review and a meta-analysis was performed to combine the results from several trials and to estimate the pooled (overall) effect of hazelnuts on blood lipids and body weight outcomes. Specifically, a Bayesian random effect meta-analysis of mean differences of ∆-changes from baseline across treatment (MD∆) (i.e., hazelnut-enriched diet vs. control diet) has been conducted. Nine studies representing 425 participants were included in the analysis. The intervention diet lasted 28–84 days with a dosage of hazelnuts ranging from 29 to 69 g/day. Out of nine studies, three randomized studies have been meta-analyzed showing a significant reduction in low-density lipoprotein (LDL) cholesterol (pooled MD∆ = −0.150 mmol/L; 95% highest posterior density interval (95% HPD) = −0.308; −0.003) in favor of a hazelnut-enriched diet. Total cholesterol showed a marked trend toward a decrease (pooled MD∆ = −0.127 mmol/L; 95% HPD = −0.284; 0.014) and high-density lipoprotein (HDL) cholesterol remained substantially stable (pooled MD∆ = 0.002 mmol/L; 95% HPD = −0.140; 0.147). No effects on triglycerides (pooled MD∆ = 0.045 mmol/L; 95% HPD = −0.195; 0.269) and body mass index (BMI) (pooled MD∆ = 0.062 kg/m2 ; 95% HPD = −0.293; 0.469) were found. Hazelnut-enriched diet is associated with a decrease of LDL and total cholesterol, while HDL cholesterol, triglycerides and BMI remain substantially unchanged.

Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis, and dose-response of 61 controlled intervention trials.

Del Gobbo, L.C., M.C. Falk, R. Feldman, K. Lewis, D. Mozaffarian, 2015. Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis, and dose-response of 61 controlled intervention trials. AJCN. First published ahead of print November 11, 2015 as doi: 10.3945/ajcn.115.110965.

Background: The effects of nuts on major cardiovascular disease (CVD) risk factors, including dose-responses and potential heterogeneity by nut type or phytosterol content, are not well established. Objectives: We examined the effects of tree nuts (walnuts, pistachios, macadamia nuts, pecans, cashews, almonds, hazelnuts, and Brazil nuts) on blood lipids [total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein, and triglycerides], lipoproteins [apolipoprotein A1, apolipoprotein B (ApoB), and apolipoprotein B100], blood pressure, and inflammation (C-reactive protein) in adults aged $18 y without prevalent CVD. Design: We conducted a systematic review and meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Two investigators screened 1301 potentially eligible PubMed articles in duplicate. We calculated mean differences between nut intervention and control arms, dose-standardized to one 1-oz (28.4 g) serving/d, by using inverse-variance fixed-effects meta-analysis. Dose-response for nut intake was examined by using linear regression and fractional polynomial modeling. Heterogeneity by age, sex, background diet, baseline risk factors, nut type, disease condition, duration, and quality score was assessed with meta-regression. Publication bias was evaluated by using funnel plots and Egger’s and Begg’s tests. Results: Sixty-one trials met eligibility criteria (n = 2582). Interventions ranged from 3 to 26 wk. Nut intake (per serving/d) lowered total cholesterol (24.7 mg/dL; 95% CI: 25.3, 24.0 mg/dL), LDL cholesterol (24.8 mg/dL; 95% CI: 25.5, 24.2 mg/dL), ApoB (23.7 mg/dL; 95% CI: 25.2, 22.3 mg/dL), and triglycerides (22.2 mg/dL; 95% CI: 23.8, 20.5 mg/dL) with no statistically significant effects on other outcomes. The dose-response between nut intake and total cholesterol and LDL cholesterol was nonlinear (P-nonlinearity , 0.001 each); stronger effects were observed for $60 g nuts/d. Significant heterogeneity was not observed by nut type or other factors. For ApoB, stronger effects were observed in populations with type 2 diabetes (211.5 mg/dL; 95% CI: 216.2, 26.8 mg/dL) than in healthy populations (22.5 mg/dL; 95% CI: 24.7, 20.3 mg/dL) (P-heterogeneity = 0.015). Little evidence of publication bias was found. Conclusions: Tree nut intake lowers total cholesterol, LDL cholesterol, ApoB, and triglycerides. The major determinant of cholesterol lowering appears to be nut dose rather than nut type. Our findings also highlight the need for investigation of possible stronger effects at high nut doses and among diabetic populations.

Nuts and CVD.

Ros, E., 2015. Nuts and CVD. Br J Nutr. 113, S111–S120.

Nuts are nutrient-dense foods with complex matrices rich in unsaturated fatty acids and other bioactive compounds, such as l-arginine, fibre, healthful minerals, vitamin E, phytosterols and polyphenols. By virtue of their unique composition, nuts are likely to beneficially affect cardiovascular health. Epidemiological studies have associated nut consumption with a reduced incidence of CHD in both sexes and of diabetes in women, but not in men. Feeding trials have clearly demonstrated that consumption of all kinds of nuts has a cholesterol-lowering effect, even in the context of healthy diets. There is increasing evidence that nut consumption has a beneficial effect on oxidative stress, inflammation and vascular reactivity. Blood pressure, visceral adiposity and the metabolic syndrome also appear to be positively influenced by nut consumption. Contrary to expectations, epidemiological studies and clinical trials suggest that regular nut consumption is not associated with undue weight gain. Recently, the PREvención con DIeta MEDiterránea randomised clinical trial of long-term nutrition intervention in subjects at high cardiovascular risk provided first-class evidence that regular nut consumption is associated with a 50% reduction in incident diabetes and, more importantly, a 30% reduction in CVD. Of note, incident stroke was reduced by nearly 50% in participants allocated to a Mediterranean diet enriched with a daily serving of mixed nuts (15 g walnuts, 7·5 g almonds and 7·5 g hazelnuts). Thus, it is clear that frequent nut consumption has a beneficial effect on CVD risk that is likely to be mediated by salutary effects on intermediate risk factors.

Tree Nut consumption is associated with better adiposity measures and cardiovascular and metabolic syndrome health risk factors in U.S. Adults: NHANES 2005–2010.

O’Neil, C.E., V.L. Fulgoni, T.A. Nicklas, 2015. Tree Nut consumption is associated with better adiposity measures and cardiovascular and metabolic syndrome health risk factors in U.S. Adults: NHANES 2005–2010. Nutrition Journal. 14:64. DOI 10.1186/s12937-015-0052-x

Introduction: Previous research has shown inconsistencies in the association of tree nut consumption with risk factors for cardiovascular disease (CVD) and metabolic syndrome (MetS). Objective: To determine the association of tree nut consumption with risk factors for CVD and for MetS in adults. Methods: NHANES 2005–2010 data were used to examine the associations of tree nut consumption with health risks in adults 19+ years (n = 14,386; 51 % males). Tree nuts were: almonds, Brazil nuts, cashews, filberts [hazelnuts], macadamias, pecans, pine nuts, pistachios, and walnuts. Group definitions were non-consumers < ¼ ounce/day and consumers of ≥ ¼ ounce/day tree nuts using data from 24-h dietary recalls. Means and ANOVA (covariate adjusted) were determined using appropriate sample weights. Using logistic regression, odds ratios of being overweight (OW)/obese (OB) (body mass index [BMI] >25/<30 and ≥30, respectively) and having CVRF or MetS, were determined. Results: Tree nut consumption was associated with lower BMI (p = 0.004), waist circumference (WC) (p = 0.008), systolic blood pressure (BP) (p = 0.001), Homeostatic Model Assessment—Insulin Resistance (p = 0.043), and higher high density lipoprotein-cholesterol (p = 0.022), compared with no consumption, and a lower likelihood of OB (−25 %), OW/OB (−23 %), and elevated WC (−21 %). Conclusions: Tree nut consumption was associated with better weight status and some CVRF and MetS components.