This systematic review identified low-certainty evidence indicating that omnivores are attached to meat and have low willingness to reduce meat consumption. People following a diet with low or no meat consumption cite health as a main reason for that diet. The findings of this systematic review are likely to be robust. However, due to only including studies conducted in Europe, Australia, Canada, the United States, and New Zealand, the results are not generalisable to other settings, e.g. lower income countries.
Overall summary Low risk of bias in the review
No relevant concerns were identified.
|A. Did the interpretation of findings address all of the concerns identified in Domains 1 to 4?||Probably yes|
|B. Was the relevance of identified studies to the review's research question appropriately considered?||Probably yes|
|C. Did the reviewers avoid emphasizing results on the basis of their statistical significance?||Probably yes|
|Risk of bias in the review||Low|
|Number of studies||54|
|Number of participants||74652|
|Last search date||June 2019|
|Review type||Mixed-methods review of values and preferences|
|Objective||To evaluate health-related values and preferences regarding meat consumption.|
|Population||Studies were included if >80% of the participants were adults (aged ≥18 years).|
|Outcome||Health-related values and preferences on meat consumption.|
|Study design||Quantitative (i.e. cross-sectional design), qualitative (e.g. participant interviews, focus groups), and mixed-methods studies.
Studies had to be conducted in Europe, Australia, Canada, the United States, and New Zealand.
This mixed-method systematic review identified 13 studies for the qualitative synthesis and another 41 studies for the quantitative synthesis.The review identified several themes related to meat consumption.
Most omnivores are highly attached to meat (19 quantitative studies, 3 qualitative studies) where men had a more positive attitude towards meat than women (10 qualitative studies). Similarly, most omnivores reported a low willingness to reduce meat consumption (5 quantitative studies, 4 qualitative studies).
Elderly omnivores were generally concerned about health in respect to their food choices (3 qualitative studies) and believed that aging is associated with a decline in food intake (2 qualitative studies).
Health was cited as of the main reasons for not eating meat in vegetarians and low-meat consumers (17 quantitative studies). For many vegetarians, health concern was the primary motivation to stop eating meat (6 qualitative studies).
The certainty of evidence was rated to be low for all identified themes.
The research objective was clearly stated. The reported inclusion criteria appear to be appropriate. No language or publication status restrictions were applied, however only studies conducted in Europe, Australia, Canada, the United States, and New Zealand were included as these were considered to be homogeneous countries reflecting similar socioeconomic characteristics and values.
|1.1 Did the review adhere to pre-defined objectives and eligibility criteria?||Yes|
|1.2 Were the eligibility criteria appropriate for the review question?||Probably yes|
|1.3 Were eligibility criteria unambiguous?||Yes|
|1.4 Were all restrictions in eligibility criteria based on study characteristics appropriate (e.g. date, sample size, study quality, outcomes measured)?||Probably yes|
|1.5 Were any restrictions in eligibility criteria based on sources of information appropriate (e.g. publication status or format, language, availability of data)?||Yes|
|Concerns regarding specification of study eligibility criteria||Low|
MEDLINE, Embase, Web of Science, Centre for Agriculture and Biosciences Abstracts, International System for Agricultural Science and Technology, and Food Science and Technology Abstracts were searched from inception to July 2018 and update searches were undertaken (MEDLINE and Embase only) to June 2019. Bibliographies of included articles and relevant literature reviews were screened for additional articles. The search strategies used for each database were published in full (supplementary material) and appeared adequate. No date or language limitations were applied. Two reviewers independently assessed studies for inclusion and any disagreements were resolved through discussion or consultation with a third reviewer.
|2.1 Did the search include an appropriate range of databases/electronic sources for published and unpublished reports?||Probably yes|
|2.2 Were methods additional to database searching used to identify relevant reports?||Yes|
|2.3 Were the terms and structure of the search strategy likely to retrieve as many eligible studies as possible?||Probably yes|
|2.4 Were restrictions based on date, publication format, or language appropriate?||Yes|
|2.5 Were efforts made to minimise error in selection of studies?||Yes|
|Concerns regarding methods used to identify and/or select studies||Low|
Two reviewers independently extracted data from included studies, using ad hoc data extraction forms for quantitative and qualitative research (included in the supplemental material), and any disagreements were resolved through discussion or consultation with a third reviewer. Risk of bias of quantitative studies was assessed using an adapted version of the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach to assess risk of bias of studies on importance of outcomes or values and preferences. For qualitative studies, the Critical Appraisal Skill Programme qualitative research checklist was used. Risk of bias was assessed independently by two reviewers and any disagreements were resolved through discussion or consultation with a third reviewer. Some baseline characteristics are reported for the identified studies.
|3.1 Were efforts made to minimise error in data collection?||Yes|
|3.2 Were sufficient study characteristics considered for both review authors and readers to be able to interpret the results?||Probably yes|
|3.3 Were all relevant study results collected for use in the synthesis?||Probably yes|
|3.4 Was risk of bias (or methodological quality) formally assessed using appropriate criteria?||Probably yes|
|3.5 Were efforts made to minimise error in risk of bias assessment?||Yes|
|Concerns regarding methods used to collect data and appraise studies||Low|
Results were synthesised using a 4-step approach which involved simultaneous quantitative and qualitative data collection and analysis. Eligible articles were selected, key themes identified and coded, these were used to inform the data extraction forms. Through an iterative process, key themes were compared across all studies and analytic themes identified. Meta-narrative synthesis was used to transform the quantitative data into qualitative data. Results are presented narratively. Certainty of evidence was assessed and presented.
|4.1 Did the synthesis include all studies that it should?||Probably yes|
|4.2 Were all pre-defined analyses reported or departures explained?||Probably yes|
|4.3 Was the synthesis appropriate given the degree of similarity in the research questions, study designs and outcomes across included studies?||Probably yes|
|4.4 Was between-study variation minimal or addressed in the synthesis?||Probably yes|
|4.5 Were the findings robust, e.g. as demonstrated through funnel plot or sensitivity analyses?||Probably yes|
|4.6 Were biases in primary studies minimal or addressed in the synthesis?||Probably yes|
|Concerns regarding synthesis and findings||Low|
Purpose: To identify and evaluate evidence addressing health-related values and preferences regarding meat consumption. Data Sources: MEDLINE, EMBASE, Web of Science, Centre for Agriculture and Biosciences Abstracts, International System for Agricultural Science and Technology, and Food Science and Technology Abstracts were searched from inception to July 2018 without language restrictions. Study Selection: Pairs of reviewers independently screened search results and included quantitative and qualitative studies reporting adults' health-related values and preferences regarding meat consumption. Data Extraction: Pairs of reviewers independently extracted data and assessed risk of bias. Data Synthesis: Data were synthesized into narrative form, and summaries were tabulated and certainty of evidence was assessed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. Of 19 172 initial citations, 41 quantitative studies (38 addressed reasons for meat consumption and 5 addressed willingness to reduce meat consumption) and 13 qualitative studies (10 addressed reasons for meat consumption and 4 addressed willingness to reduce meat consumption) were eligible for inclusion. Thirteen studies reported that omnivores enjoy eating meat, 18 reported that these persons consider meat an essential component of a healthy diet, and 7 reported that they believe they lack the skills needed to prepare satisfactory meals without meat. Omnivores are generally unwilling to change their meat consumption. The certainty of evidence was low for both “reasons for meat consumption” and “willingness to reduce meat consumption in the face of undesirable health effects.” Limitation: Limited generalizability of findings to lower-income countries, low-certainty evidence for willingness to reduce meat consumption, and limited applicability to specific types of meat (red and processed meat). Conclusion: Low-certainty evidence suggests that omnivores are attached to meat and are unwilling to change this behavior when faced with potentially undesirable health effects. Primary Funding Source: None. (PROSPERO: CRD42018088854)