Cited by 150Nuts composition and effectsNutritional Studies and DietDiabetes, Cardiovascular Risks, and Lipoproteins

Effect of tree nuts on metabolic syndrome criteria: a systematic review and meta-analysis of randomised controlled trials

Open access
Blanco Mejia, Sonia, Kendall, Cyril W C, Viguiliouk, Effie, Augustin, Livia S, Ha, Vanessa, Cozma, Adrian I, Mirrahimi, Arash, Maroleanu, Adriana +5 more·2014·BMJ Open

Abstract

Objective: To provide a broader evidence summary to inform dietary guidelines of the effect of tree nuts on criteria of the metabolic syndrome (MetS). Design: We conducted a systematic review and meta-analysis of the effect of tree nuts on criteria of the MetS. Data sources: We searched MEDLINE, EMBASE, CINAHL and the Cochrane Library (through 4 April 2014). Eligibility criteria for selecting studies: We included relevant randomised controlled trials (RCTs) of ≥3 weeks reporting at least one criterion of the MetS. Data extraction: Two or more independent reviewers extracted all relevant data. Data were pooled using the generic inverse variance method using random effects models and expressed as mean differences (MD) with 95% CIs. Heterogeneity was assessed by the Cochran Q statistic and quantified by the I 2 statistic. Study quality and risk of bias were assessed. Results: Eligibility criteria were met by 49 RCTs including 2226 participants who were otherwise healthy or had dyslipidaemia, MetS or type 2 diabetes mellitus. Tree nut interventions lowered triglycerides (MD=−0.06 mmol/L (95% CI −0.09 to −0.03 mmol/L)) and fasting blood glucose (MD=−0.08 mmol/L (95% CI −0.16 to −0.01 mmol/L)) compared with control diet interventions. There was no effect on waist circumference, high-density lipoprotein cholesterol or blood pressure with the direction of effect favouring tree nuts for waist circumference. There was evidence of significant unexplained heterogeneity in all analyses (p<0.05). Conclusions: Pooled analyses show a MetS benefit of tree nuts through modest decreases in triglycerides and fasting blood glucose with no adverse effects on other criteria across nut types. As our conclusions are limited by the short duration and poor quality of the majority of trials, as well as significant unexplained between-study heterogeneity, there remains a need for larger, longer, high-quality trials. Trial registration number: NCT01630980.

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  • Systematic reviews and meta-analyses of the available randomized controlled trials of nuts have only shown non-significant reductions in blood pressure.

    “however, systematic reviews and meta-analyses of the available randomized controlled trials have only shown non-significant reductions.43”

    From Portfolio Dietary Pattern and Cardiovascular Disease: A Systematic Review and Meta-analysis of Controlled Trials (2018) · cites this paper as [43]

    The Results section (“Blood pressure”) reports no statistically significant effect, but the pooled estimates for both systolic and diastolic blood pressure are positive, not reductions (MD=0.07 and 0.23 mm Hg, respectively). The Discussion likewise describes a lack of improvement in blood pressure. (LLM, conf=0.88)

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  • Systematic reviews and meta-analyses of randomized controlled trials have shown beneficial effects of nuts on non-HDL-C, apoB, TC, and TG.

    “Systematic reviews and meta-analyses of randomized controlled trials have shown beneficial effects of plant sterols, 38,39 viscous fibres, 37,40,41 plant proteins, 34 and nuts 33,42,43 on the established alternate lipid targets, non-HDL-C and apoB, and other blood lipids including TC and TG.”

    From Portfolio Dietary Pattern and Cardiovascular Disease: A Systematic Review and Meta-analysis of Controlled Trials (2018) · cites this paper as [43]

    The Results > Triglycerides section (page not provided) reports that tree nuts significantly lowered TG in a meta-analysis of randomized trials. The Methods > Data extraction section (page not provided) lists the outcomes analyzed; this paper does not establish benefits for non-HDL-C, apoB, or TC. (LLM, conf=0.88)

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Research works printed but not linked: 2

  1. [26]US Food and Drug Administration. Guidance for industry: evidence-based review system for the scientific evaluation of health claims—final, 2009
  2. [53]Berryman CE West SG Bordi PL Daily inclusion of almonds (1.5 ounces) in a cholesterol-lowering diet maintains HDL-cholesterol and HDL subclasses in mildly hypercholesterolemic adults. Ann Nutr Metab 2013; 63: 1338

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Authors
Blanco Mejia, S., Kendall, C. W. C., Viguiliouk, E., Augustin, L. S., Ha, V., Cozma, A. I., Mirrahimi, A., Maroleanu, A., Chiavaroli, L., Leiter, L. A., de Souza, R. J., Jenkins, D. J. A., & Sievenpiper, J. L.
Affiliations
  • Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
  • St. Michael's Hospital (CA)
Corresponding author
Kendall, Cyril W C
Venue
BMJ Open
Publisher
BMJ
Published
2014-07
Volume
4
Issue
7
Pages
e004660
ISSN
2044-6055 (ISSN-L)
OpenAlex
W2113378946
Cited by
150
References
85
Citations by year
2026: 3 · 2025: 3 · 2024: 23 · 2023: 13 · 2022: 9 · 2021: 22 · 2020: 16 · 2019: 9 · 2018: 14 · 2017: 16 · 2016: 6 · 2015: 15 · 2014: 1
FWCI
1.45
Type
journal article
Language
en
Open access
Licence
cc-by-nc
Locations
  • BMJ Open (publishedVersion, cc-by-nc)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by-nc)
  • PubMed Central (publishedVersion, cc-by-nc)
  • PubMed (publishedVersion)
  • HighWire Press Open Archive (submittedVersion)
Funders
  • Coca-Cola Foundation
  • Innovative Research Group Project of the National Natural Science Foundation of China
  • Canola Council of Canada
  • Canadian Institutes of Health Research (129920)
Topics
  • Health Sciences › Nursing › Nutrition and Dietetics › Nuts composition and effects
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Nutritional Studies and Diet
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diabetes, Cardiovascular Risks, and Lipoproteins
Keywords
tree nuts, metabolic syndrome, triglycerides, fasting blood glucose, waist circumference, HDL cholesterol, blood pressure, dietary intervention, dyslipidemia, type 2 diabetes, dietary guidelines
MeSH terms
Humans, Lipids, Nuts, Trees, Randomized Controlled Trials as Topic, Metabolic Syndrome, Lipid Metabolism

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