Dena Zeraatkar, MSc; Bradley C. Johnston, PhD; Jessica Bartoszko, HBSc; Kevin Cheung, MD; Malgorzata M. Bala, MD, PhD; Claudia Valli, MSc; Montserrat Rabassa, PhD; Daegen Sit, MD; Kirolos Milio, BSc; Behnam Sadeghirad, PharmD; Arnav Agarwal, MD; Adriana M. Zea, RD; Yung Lee, BHSc; Mi Ah Han, MD, PhD; Robin W.M. Vernooij, PhD; Pablo Alonso-Coello, MD, PhD; Gordon H. Guyatt, MD; Regina El Dib, PhD
Acknowledgment: The authors thank Thomasin Adams-Webber (Hospital for Sick Children) for her help designing our search strategy.
Disclosures: Dr. El Dib received a São Paulo Research Foundation (FAPESP) (2018/11205-6) scholarship and funding from the National Council for Scientific and Technological Development (CNPq) (CNPq 310953/2015-4) and the Faculty of Medicine, Dalhousie University. Authors not named here have disclosed no conflicts of interest. Disclosures can also be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M19-0622.
Editors' Disclosures: Christine Laine, MD, MPH, Editor in Chief, reports that her spouse has stock options/holdings with Targeted Diagnostics and Therapeutics. Darren B. Taichman, MD, PhD, Executive Editor, reports that he has no financial relationships or interests to disclose. Cynthia D. Mulrow, MD, MSc, Senior Deputy Editor, reports that she has no relationships or interests to disclose. Jaya K. Rao, MD, MHS, Deputy Editor, reports that she has stock holdings/options in Eli Lilly and Pfizer. Catharine B. Stack, PhD, MS, Deputy Editor, Statistics, reports that she has stock holdings in Pfizer, Johnson & Johnson, and Colgate-Palmolive. Christina C. Wee, MD, MPH, Deputy Editor, reports employment with Beth Israel Deaconess Medical Center. Sankey V. Williams, MD, Deputy Editor, reports that he has no financial relationships or interests to disclose. Yu-Xiao Yang, MD, MSCE, Deputy Editor, reports that he has no financial relationships or interest to disclose.
>Reproducible Research Statement: Study protocol: Available at PROSPERO (CRD42017074074). Statistical code and data set: Available from Dr. Johnston (e-mail, email@example.com).
Corresponding Author: Bradley C. Johnston, PhD, Department of Community Health and Epidemiology, Dalhousie University, Centre for Clinical Research, Room 404, 5790 University Avenue, Halifax, Nova Scotia B3H 1V7, Canada; e-mail, firstname.lastname@example.org.
Current Author Addresses: Ms. Zeraatkar, Ms. Bartoszko, Drs. Sadeghirad and Guyatt, and Ms. Perdomo: Department of Health Research Methods, Evidence, and Impact, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada.
Dr. Johnston: Department of Community Health and Epidemiology, Dalhousie University, Centre for Clinical Research, Room 404, 5790 University Avenue, Halifax, Nova Scotia, B3H 1V7, Canada.
Dr. Cheung: 114 Loganberry Crescent, Toronto, Ontario M2H 3H1, Canada.
Dr. Bala: Jagiellonian University Medical College, Department of Hygiene and Dietetics, 7 Kopernika Street, 31-034 Kraków, Poland.
Ms. Valli and Drs. Rabassa and Alonso-Coello: Iberoamerican Cochrane Centre, Instituto de Investigación Biomédica de Sant Pau (IIB Sant Pau-CIBERESP), Carrer de Sant Antoni Maria Claret 167, Barcelona 08025, Spain.
Dr. Sit: University of British Columbia, 107-1165 West 13th Avenue, Vancouver, British Columbia V6H 1N4, Canada.
Mr. Milio: 592 Regal Place, Waterloo, Ontario N2V 2G3, Canada.
Dr. Agarwal: Department of Medicine, University of Toronto, Suite RFE 3-805, 200 Elizabeth Street, Toronto, Ontario M5G 2C4, Canada.
Ms. Zea: Clinica Las Americas, Diagonal 75B, North 2A-80/140, Medellin, Colombia.
Mr. Lee: 30 White Lodge Crescent, Richmond Hill, Ontario L4C 9A1, Canada.
Dr. Han: Department of Preventive Medicine, College of Medicine, Chosun University, 309 Philmun-daero, Dong-gu, Gwangju 61452, Korea.
Dr. Vernooij: Department of Research, Netherlands Comprehensive Cancer Organisation, Godebaldkwartier 419, Utrecht 3511 DT, the Netherlands.
Dr. El Dib: Institute of Science and Technology, São José dos Campos, Avenida Engenheiro Francisco José Longo, 777, Jardim São Dimas, São Paulo 12245-000, Brazil.
Author Contributions: Conception and design: D. Zeraatkar, B.C. Johnston, M.M. Bala, P. Alonso-Coello, G.H. Guyatt, R. El Dib.
Analysis and interpretation of the data: D. Zeraatkar, B.C. Johnston, M.M. Bala, M. Rabassa, D. Sit, M.A. Han, P. Alonso-Coello, G.H. Guyatt, R. El Dib.
Drafting of the article: B.C. Johnston, R. El Dib.
Critical revision of the article for important intellectual content: D. Zeraatkar, B.C. Johnston, M.M. Bala, D. Sit, B. Sadeghirad, A.M. Zea, Y. Lee, M.A. Han, R.W.M. Vernooij, P. Alonso-Coello, G.H. Guyatt, R. El Dib.
Final approval of the article: D. Zeraatkar, B.C. Johnston, J. Bartoszko, K. Cheung, M.M. Bala, C. Valli, M. Rabassa, D. Sit, K. Milio, B. Sadeghirad, A. Agarwal, A.M. Zea, Y. Lee, M.A. Han, R.W.M. Vernooij, P. Alonso-Coello, G.H. Guyatt, R. El Dib.
Provision of study materials or patients: B.C. Johnston, R. El Dib.
Administrative, technical, or logistic support: D. Zeraatkar, B.C. Johnston, R. El Dib.
Collection and assembly of data: D. Zeraatkar, B.C. Johnston, J. Bartoszko, K. Cheung, M.M. Bala, C. Valli, M. Rabassa, D. Sit, K. Milio, B. Sadeghirad, A. Agarwal, A.M. Zea, Y. Lee, M. Han, R.W.M. Vernooij, R. El Dib.
Few randomized trials have evaluated the effect of reducing red meat intake on clinically important outcomes.
To summarize the effect of lower versus higher red meat intake on the incidence of cardiometabolic and cancer outcomes in adults.
EMBASE, CENTRAL, CINAHL, Web of Science, and ProQuest from inception to July 2018 and MEDLINE from inception to April 2019, without language restrictions.
Randomized trials (published in any language) comparing diets lower in red meat with diets higher in red meat that differed by a gradient of at least 1 serving per week for 6 months or more.
Teams of 2 reviewers independently extracted data and assessed the risk of bias and the certainty of the evidence.
Of 12 eligible trials, a single trial enrolling 48 835 women provided the most credible, though still low-certainty, evidence that diets lower in red meat may have little or no effect on all-cause mortality (hazard ratio [HR], 0.99 [95% CI, 0.95 to 1.03]), cardiovascular mortality (HR, 0.98 [CI, 0.91 to 1.06]), and cardiovascular disease (HR, 0.99 [CI, 0.94 to 1.05]). That trial also provided low- to very-low-certainty evidence that diets lower in red meat may have little or no effect on total cancer mortality (HR, 0.95 [CI, 0.89 to 1.01]) and the incidence of cancer, including colorectal cancer (HR, 1.04 [CI, 0.90 to 1.20]) and breast cancer (HR, 0.97 [0.90 to 1.04]).
There were few trials, most addressing only surrogate outcomes, with heterogeneous comparators and small gradients in red meat consumption between lower versus higher intake groups.
Low- to very-low-certainty evidence suggests that diets restricted in red meat may have little or no effect on major cardiometabolic outcomes and cancer mortality and incidence.
None (PROSPERO: CRD42017074074).
Zeraatkar D, Johnston BC, Bartoszko J, et al. Effect of Lower Versus Higher Red Meat Intake on Cardiometabolic and Cancer Outcomes: A Systematic Review of Randomized Trials. Ann Intern Med. 2019;171:721–731. [Epub ahead of print 1 October 2019]. doi: https://doi.org/10.7326/M19-0622
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Published: Ann Intern Med. 2019;171(10):721-731.
Published at www.annals.org on 1 October 2019
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