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Original research
Nutrition users’ guides: systematic reviews part 1 –structured guide for methodological assessment, interpretation and application of systematic reviews and meta-analyses of non-randomised nutritional epidemiology studies
  1. Dena Zeraatkar1,2,
  2. Russell J de Souza1,
  3. Gordon H Guyatt1,3,
  4. Malgorzata M Bala4,
  5. Pablo Alonso-Coello5,6,7 and
  6. Bradley C Johnston8,9,10
  1. 1Department of Health Research Methods, Evidence & Impact, McMaster University, Hamilton, Ontario, Canada
  2. 2Department of Anesthesia, McMaster University, Hamilton, Ontario, Canada
  3. 3Department of Medicine, McMaster University, Hamilton, Ontario, Canada
  4. 4Chair of Epidemiology and Preventive Medicine, Department of Hygiene and Dietetics, Jagiellonian University Medical College, Krakow, Poland
  5. 5Iberomerican Cochrane Centre, Clinical Epidemiology and Public Health Department, Institute of Biomedical Research of Barcelona, Barcelona, Spain
  6. 6Institut de Recerca Sant Pau (IR SANT PAU), Sant Quintí, Barcelona, Spain
  7. 7Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
  8. 8Department of Nutrition, College of Agriculture and Life Sciences, Texas A&M University, College Station, Texas, USA
  9. 9Department of Epidemiology & Biostatistics, School of Public Health, Texas A&M University, College Station, Texas, USA
  10. 10Health Research Methods, Evidence and Impact, McMaster University, Hamilton, Ontario, Canada
  1. Correspondence to Dr Bradley C Johnston; bradley.johnston{at}tamu.edu; Dr Dena Zeraatkar; dena.zera{at}gmail.com

Abstract

Due to the challenges of conducting randomised controlled trials (randomised trials) of dietary interventions, evidence in nutrition often comes from non-randomised (observational) studies of nutritional exposures—called nutritional epidemiology studies. When using systematic reviews of such studies to advise patients or populations on optimal dietary habits, users of the evidence (eg, healthcare professionals such as clinicians, health service and policy workers) should first evaluate the rigour (validity) and utility (applicability) of the systematic review. Issues in making this judgement include whether the review addressed a sensible question; included an exhaustive literature search; was scrupulous in the selection of studies and the collection of data; and presented results in a useful manner. For sufficiently rigorous and useful reviews, evidence users must subsequently evaluate the certainty of the findings, which depends on assessments of risk of bias, inconsistency, imprecision, indirectness, effect size, dose-response and the likelihood of publication bias. Given the challenges of nutritional epidemiology, evidence users need to be diligent in assessing whether studies provide evidence of sufficient certainty to allow confident recommendations for patients regarding nutrition and dietary interventions.

  • Dietary patterns
  • Nutritional treatment
  • Medical education
  • Evidence based practice
  • Critical appraisal
  • Nutrition

Data availability statement

Data sharing not applicable as no data sets generated and/or analysed for this study.

http://creativecommons.org/licenses/by-nc/4.0/

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, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/bmjnph-2023-000835

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    Data availability statement

    Data sharing not applicable as no data sets generated and/or analysed for this study.

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    Footnotes

    • X @DenaZera, @PabloACoello, @methodsnerd

    • Contributors DZ, BCJ and GHG conceptualised the paper. DZ and BCJ drafted the paper. RJdS, GHG, MMB, and PA-C provided critical feedback. DZ, MMB, PA-C, RJdS, GHG and BCJ revised the paper. DZ and BCJ provided technical support. All authors reviewed the semi-final version and approved the final version for publication. DZ and BCJ are guarators.

    • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

    • Competing interests GHG, BCJ, MMB, PA-C and DZ are GRADE working group members. BCJ has received a start-up grant from Texas A&M AgriLife Research to fund investigator-initiated research related to saturated and polyunsaturated fats. The grant was from Texas A&M AgriLife institutional funds from interest and investment earnings, not a sponsoring organisation, industry or company. BCJ also holds National Institute of Diabetes, Digestive and Kidney Diseases R25 funds to support training in evidence-based nutrition practice. Other authors claim no disclosures.

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