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

Abstract

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 (-4.7 mg/dL; 95% CI: -5.3, -4.0 mg/dL), LDL cholesterol (-4.8 mg/dL; 95% CI: -5.5, -4.2 mg/dL), ApoB (-3.7 mg/dL; 95% CI: -5.2, -2.3 mg/dL), and triglycerides (-2.2 mg/dL; 95% CI: -3.8, -0.5 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 (-11.5 mg/dL; 95% CI: -16.2, -6.8 mg/dL) than in healthy populations (-2.5 mg/dL; 95% CI: -4.7, -0.3 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.

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  • Authors+Show Affiliations

    ,

    Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA; and delgobbo@stanford.edu.

    ,

    Life Sciences Research Organization, Bethesda, MD.

    ,

    Life Sciences Research Organization, Bethesda, MD.

    ,

    Life Sciences Research Organization, Bethesda, MD.

    Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA; and.

    Source

    MeSH

    Apolipoproteins B
    Cholesterol
    Cholesterol, LDL
    Controlled Clinical Trials as Topic
    Diabetes Mellitus, Type 2
    Diabetic Angiopathies
    Down-Regulation
    Evidence-Based Medicine
    Humans
    Hyperlipidemias
    Hypertension
    Nuts
    Trees

    Pub Type(s)

    Comparative Study
    Journal Article
    Meta-Analysis
    Research Support, N.I.H., Extramural
    Review
    Systematic Review

    Language

    eng

    PubMed ID

    26561616

    Citation

    Del Gobbo, Liana C., et al. "Effects of Tree Nuts On Blood Lipids, Apolipoproteins, and Blood Pressure: Systematic Review, Meta-analysis, and Dose-response of 61 Controlled Intervention Trials." The American Journal of Clinical Nutrition, vol. 102, no. 6, 2015, pp. 1347-56.
    Del Gobbo LC, Falk MC, Feldman R, et al. Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis, and dose-response of 61 controlled intervention trials. Am J Clin Nutr. 2015;102(6):1347-56.
    Del Gobbo, L. C., Falk, M. C., Feldman, R., Lewis, K., & Mozaffarian, D. (2015). Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis, and dose-response of 61 controlled intervention trials. The American Journal of Clinical Nutrition, 102(6), pp. 1347-56. doi:10.3945/ajcn.115.110965.
    Del Gobbo LC, et al. Effects of Tree Nuts On Blood Lipids, Apolipoproteins, and Blood Pressure: Systematic Review, Meta-analysis, and Dose-response of 61 Controlled Intervention Trials. Am J Clin Nutr. 2015;102(6):1347-56. PubMed PMID: 26561616.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis, and dose-response of 61 controlled intervention trials. AU - Del Gobbo,Liana C, AU - Falk,Michael C, AU - Feldman,Robin, AU - Lewis,Kara, AU - Mozaffarian,Dariush, Y1 - 2015/11/11/ PY - 2015/03/11/received PY - 2015/09/23/accepted PY - 2015/11/13/entrez PY - 2015/11/13/pubmed PY - 2016/4/14/medline KW - apolipoprotein KW - cardiovascular KW - cholesterol KW - lipids KW - nuts SP - 1347 EP - 56 JF - The American journal of clinical nutrition JO - Am. J. Clin. Nutr. VL - 102 IS - 6 N2 - 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 (-4.7 mg/dL; 95% CI: -5.3, -4.0 mg/dL), LDL cholesterol (-4.8 mg/dL; 95% CI: -5.5, -4.2 mg/dL), ApoB (-3.7 mg/dL; 95% CI: -5.2, -2.3 mg/dL), and triglycerides (-2.2 mg/dL; 95% CI: -3.8, -0.5 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 (-11.5 mg/dL; 95% CI: -16.2, -6.8 mg/dL) than in healthy populations (-2.5 mg/dL; 95% CI: -4.7, -0.3 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. SN - 1938-3207 UR - https://www.unboundmedicine.com/medline/citation/26561616/full_citation L2 - https://academic.oup.com/ajcn/article-lookup/doi/10.3945/ajcn.115.110965 DB - PRIME DP - Unbound Medicine ER -