Mi Ah Han, MD, PhD; Dena Zeraatkar, MSc; Gordon H. Guyatt, MD; Robin W.M. Vernooij, PhD; Regina El Dib, PhD; Ying Zhang, PhD; Abdullah Algarni, MBBS; Gareth Leung, BHSc; Dawid Storman, MD; Claudia Valli, MSc; Montserrat Rabassa, PhD; Nadia Rehman, BDS; Michael K. Parvizian, BHSc; Max Zworth, BA⪼ Jessica J. Bartoszko, HBSc; Luciane Cruz Lopes, PhD; Daegan Sit, MD; Malgorzata M. Bala, MD, PhD; Pablo Alonso-Coello, MD, PhD; Bradley C. Johnston, PhD
Note: Drs. Han, Guyatt, and Johnston and Ms. Zeraatkar act as the guarantors of this article.
Acknowledgment: The authors thank Thomasin Adams-Webber (Hospital for Sick Children) for her help designing the 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=M19-0699.
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: Registered in PROSPERO (CRD42017074074). Statistical code: See Methods and Appendix. Code is available on request. Data set: See the tables and Appendix. Data are available on request from Dr. Han (e-mail, firstname.lastname@example.org).
Corresponding Author: Gordon H. Guyatt, MD, Department of Health Research Methods, Evidence and Impact, McMaster University, 1280 Main Street West, Hamilton, Ontario L8N 3Z5, Canada; e-mail, email@example.com.
Current Author Addresses: Dr. Han: Department of Preventive Medicine, College of Medicine, Chosun University, 309 Pilmun-daero, Dong-gu, Gwangju 61452, Korea.
Ms. Zeraatkar, Drs. Guyatt and Rehman, Mr. Leung, Mr. Parvizian, Mr. Zworth, and Ms. Bartoszko: McMaster University Health Sciences Center, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada.
Dr. Vernooij: Department of Research, Netherlands Comprehensive Cancer Organisationn, Godebaldkwartier 419, Utrecht 3511DT, the Netherlands.
Dr. El Dib: Institute of Science and Technology, Universidade Estadual Paulista, Avenida Engenheiro Francisco José Longo, 777, Jardim São Dimas, São José dos Campos, Sao Paolo 12245-000, Brazil.
Dr. Zhang: Center for Evidence-based Chinese Medicine, Beijing University, 11 Beisanhuan Dong Lu, Chaoyang District, Beijing 100029, China.
Dr. Algarni: Department of Internal Medicine, Aseer Central Hospital, 4076 Al Muruj, Unit 3, Al Rabwah, Abha 62523, Saudi Arabia.
Drs. Storman and Bala: Department of Hygiene and Dietetics, Jagiellonian University Medical College, 7 Kopernika Street, Kraków 31-034, 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. Lopes: University of Sorocaba (UNISO), Rodovia Raposo Tavares, Km 92,5, Sorocaba, Sao Paulo 180230-000, Brazil.
Dr. Sit: University of British Columbia, 107-1165 West 13th Avenue, Vancouver, British Columbia V6H 1N4, Canada.
Dr. Johnston: Department of Community Health and Epidemiology, Centre for Clinical Research, Dalhousie University, 5790 University Avenue, Room 404, Halifax, Nova Scotia B3J 0E4, Canada.
Author Contributions: Conception and design: M.A. Han, D. Zeraatkar, G.H. Guyatt, M.M. Bala, P. Alonso-Coello, B.C. Johnston.
Analysis and interpretation of the data: M.A. Han, D. Zeraatkar, R. El Dib, M. Rabassa, N. Rehman, D. Sit, M.M. Bala, P. Alonso-Coello, B.C. Johnston.
Drafting of the article: M.A. Han, R. El Dib, D. Sit, B.C. Johnston.
Critical revision of the article for important intellectual content: M.A. Han, D. Zeraatkar, G.H. Guyatt, R.W.M. Vernooij, D. Sit, M.M. Bala, P. Alonso-Coello, B.C. Johnston.
Final approval of the article: M.A. Han, D. Zeraatkar, G.H. Guyatt, R.W.M. Vernooij, R. El Dib, Y. Zhang, A. Algarni, G. Leung, D. Storman, C. Valli, M. Rabassa, N. Rehman, M.K. Parvizian, M. Zworth, J.J. Bartoszko, L.C. Lopes, D. Sit, M.M. Bala, P. Alonso-Coello, B.C. Johnston.
Statistical expertise: M.A. Han, D. Zeraatkar.
Administrative, technical, or logistic support: M.A. Han, D. Zeraatkar.
Collection and assembly of data: M.A. Han, D. Zeraatkar, R.W.M. Vernooij, Y. Zhang, A. Algarni, G. Leung, D. Storman, C. Valli, M. Rabassa, M.K. Parvizian, M. Zworth, J.J. Bartoszko, L.C. Lopes, D. Sit, B.C. Johnston.
Cancer incidence has continuously increased over the past few centuries and represents a major health burden worldwide.
To evaluate the possible causal relationship between intake of red and processed meat and cancer mortality and incidence.
Embase, Cochrane Central Register of Controlled Trials, Web of Science, CINAHL, and ProQuest from inception until July 2018 and MEDLINE from inception until April 2019 without language restrictions.
Cohort studies that included more than 1000 adults and reported the association between consumption of unprocessed red and processed meat and cancer mortality and incidence.
Teams of 2 reviewers independently extracted data and assessed risk of bias; 1 reviewer evaluated the certainty of evidence, which was confirmed or revised by the senior reviewer.
Of 118 articles (56 cohorts) with more than 6 million participants, 73 articles were eligible for the dose–response meta-analyses, 30 addressed cancer mortality, and 80 reported cancer incidence. Low-certainty evidence suggested that an intake reduction of 3 servings of unprocessed meat per week was associated with a very small reduction in overall cancer mortality over a lifetime. Evidence of low to very low certainty suggested that each intake reduction of 3 servings of processed meat per week was associated with very small decreases in overall cancer mortality over a lifetime; prostate cancer mortality; and incidence of esophageal, colorectal, and breast cancer.
Limited causal inferences due to residual confounding in observational studies, risk of bias due to limitations in diet assessment and adjustment for confounders, recall bias in dietary assessment, and insufficient data for planned subgroup analyses.
The possible absolute effects of red and processed meat consumption on cancer mortality and incidence are very small, and the certainty of evidence is low to very low.
None. (PROSPERO: CRD42017074074)
Evidence search and selection.
Table 1. Summary of Findings for Reduction of Unprocessed Red Meat Intake (3 Servings per Week) and Cancer Mortality and Incidence
Nonlinear association between processed meat intake and breast cancer incidence.
The solid black line represents the point estimate, the shaded region represents the 95% CIs, and the tick marks represent the positions of the study-specific estimates.
Table 2. Summary of Findings for Reduction of Processed Meat Intake (3 Servings per Week) and Cancer Mortality and Incidence
Nonlinear association between intake of mixed unprocessed red and processed meat and breast cancer incidence.
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Han MA, Zeraatkar D, Guyatt GH, et al. Reduction of Red and Processed Meat Intake and Cancer Mortality and Incidence: A Systematic Review and Meta-analysis of Cohort Studies. Ann Intern Med. 2019;171:711–720. [Epub ahead of print 1 October 2019]. doi: https://doi.org/10.7326/M19-0699
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Published: Ann Intern Med. 2019;171(10):711-720.
Published at www.annals.org on 1 October 2019
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