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The effect of nut consumption on markers of inflammation and endothelial function: a systematic review and meta-analysis of randomised controlled trials
  1. Elizabeth P Neale1,2,
  2. Linda C Tapsell1,2,
  3. Vivienne Guan1,
  4. Marijka J Batterham3
  1. 1 School of Medicine, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, Australia
  2. 2 Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, Australia
  3. 3 Statistical Consulting Service, School of Mathematics and Applied Statistics, Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, Australia
  1. Correspondence to Dr Elizabeth P Neale; elizan{at}uow.edu.au

Abstract

Objectives To examine the effect of nut consumption on inflammatory biomarkers and endothelial function.

Design A systematic review and meta-analysis.

Data sources MEDLINE, PubMed, Cumulative Index to Nursing and Allied Health Literature and Cochrane Central Register of Controlled Trials (all years to 13 January 2017).

Eligibility criteria Randomised controlled trials (with a duration of 3 weeks or more) or prospective cohort designs conducted in adults; studies assessing the effect of consumption of tree nuts or peanuts on C-reactive protein (CRP), adiponectin, tumour necrosis factor alpha, interleukin-6, intercellular adhesion molecule 1, vascular cell adhesion protein 1 and flow-mediated dilation (FMD).

Data extraction and analysis Relevant data were extracted for summary tables and analyses by two independent researchers. Random effects meta-analyses were conducted to explore weighted mean differences (WMD) in change or final mean values for each outcome.

Results A total of 32 studies (all randomised controlled trials) were included in the review. The effect of nut consumption on FMD was explored in nine strata from eight studies (involving 652 participants), with consumption of nuts resulting in significant improvements in FMD (WMD: 0.79%(95% CI 0.35 to 1.23)). Nut consumption resulted in small, non-significant differences in CRP (WMD: −0.01 mg/L (95% CI −0.06 to 0.03)) (26 strata from 25 studies), although sensitivity analyses suggest results for CRP may have been influenced by two individual studies. Small, non-significant differences were also found for other biomarkers of inflammation.

Conclusions This systematic review and meta-analysis of the effects of nut consumption on inflammation and endothelial function found evidence for favourable effects on FMD, a measure of endothelial function. Non-significant changes in other biomarkers indicate a lack of consistent evidence for effects of nut consumption on inflammation. The findings of this analysis suggest a need for more research in this area, with a particular focus on randomised controlled trials.

PROSPERO registration number CRD42016045424.

  • nut
  • inflammation
  • endothelial function
  • flow mediated dilation
  • systematic review

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

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Footnotes

  • Contributors Study concept and design: EPN, LCT, MJB. Acquisition, analysis or interpretation of data: all authors. Drafting of the manuscript: EPN. Critical revision of the manuscript for important intellectual content: all authors. Statistical analysis: EPN, VG, MJB. Obtained funding: LCT, EPN, MJB. Administrative, technical or material support: all authors. Study supervision: LCT and MJB.

  • Funding This study was supported by the INC International Nut and Dried Fruit Council (2016-R02)

  • Disclaimer The funders approved the study design but had no other role in the collection, management, analysis and interpretation of the data or preparation of the manuscript for submission.

  • Competing interests EPN reports personal fees from Safcol Australia, personal fees from Nuts for Life, grants from Pork Cooperative Research Centre , grants from Australian Government Department of Health, outside the submitted work. LCT reports grants from Illawarra Health and Medical Research Institute, grants from California Walnut Commission, grants from Nuts for Life; personal fees from McCormicks Science Institute, non-financial support from California Walnut Commission, outside the submitted work.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement Access to data available on request (elizan@uow.edu.au).

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