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Research Nut: Hazelnuts

Associations between nut consumption and inflammatory biomarkers

Yu, Z., V.S. Malik, N. Keum, F.B. Hu, E.L. Giovannucci, M.J. Stampfer, W.C. Willett, C.S. Fuchs, Y. Bao, 2016. Associations between nut consumption and inflammatory biomarkers. AJCN. First published ahead of print July 27, 2016 as doi: 10.3945/ajcn.116.134205.

Background: Increased nut consumption has been associated with reduced risk of cardiovascular disease and type 2 diabetes, as well as a healthy lipid profile. However, the associations between nut consumption and inflammatory biomarkers are unclear. Objective: We investigated habitual nut consumption in relation to inflammatory biomarkers in 2 large cohorts of US men and women. Design: We analyzed cross-sectional data from 5013 participants in the Nurses’ Health Study (NHS) and Health Professionals Follow-Up Study (HPFS) who were free of diabetes. Nut intake, defined as intake of peanuts and other nuts, was estimated from food frequency questionnaires, and cumulative averages from 1986 and 1990 in the NHS and from 1990 and 1994 in the HPFS were used. Plasma biomarkers were collected in 1989–1990 in the NHS and 1993–1995 in the HPFS. Multivariate linear regression was used to assess the associations of nut consumption with fasting plasma C-reactive protein (CRP, n = 4941), interleukin 6 (IL-6, n = 2859), and tumor necrosis factor receptor 2 (TNFR2, n = 2905). Results: A greater intake of nuts was associated with lower amounts of a subset of inflammatory biomarkers, after adjusting for demographic, medical, dietary, and lifestyle variables. The relative concentrations (ratios) and 95% CIs comparing subjects with nut intake of $5 times/wk and those in the categories of never or almost never were as follows: CRP: 0.80 (0.69, 0.90), P-trend = 0.0003; and IL-6: 0.86 (0.77, 0.97), P-trend = 0.006. These associations remained significant after further adjustment for body mass index. No significant association was observed with TNFR2. Substituting 3 servings of nuts/wk for 3 servings of red meat, processed meat, eggs, or refined grains/wk was associated with significantly lower CRP (all P , 0.0001) and IL-6 (P ranges from 0.001 to 0.017). Conclusion: Frequent nut consumption was associated with a healthy profile of inflammatory biomarkers.

Nut consumption and prostate cancer risk and mortality.

Wand, W., M. Yang, S.A. Kenfield, F.B. Hu, M.J. Stampfer, W.C. Willett, C.S. Fuchs, E.L. Giovannucci,  Y. Bao, 2016. Nut consumption and prostate cancer risk and mortality. British Journal of Cancer.doi:10.1038/bjc.2016.181

Background: Little is known of the association between nut consumption, and prostate cancer (PCa) incidence and survivorship. Methods: We conducted an incidence analysis and a case-only survival analysis in the Health Professionals Follow-up Study on the associations of nut consumption (updated every 4 years) with PCa diagnosis, and PCa-specific and overall mortality. Results: In 26 years, 6810 incident PCa cases were identified from 47 299 men. There was no association between nut consumption and being diagnosed with PCa or PCa-specific mortality. However, patients who consumed nuts five or more times per week after diagnosis had a significant 34% lower rate of overall mortality than those who consumed nuts less than once per month (HR=0.66, 95% CI: 0.52–0.83, P-trend=0.0005). Conclusions: There were no statistically significant associations between nut consumption, and PCa incidence or PCa-specific mortality. Frequent nut consumption after diagnosis was associated with significantly reduced overall mortality.

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.