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Dietary Patterns Systematic Review Project: Methodology

The Nutrition Evidence Library (NEL) was launched in July 2008 by the U.S. Department of Agriculture’s Center for Nutrition Policy and Promotion. The NEL uses a rigorous, transparent, and reproducible methodology to conduct systematic reviews on food- and nutrition-related topics to support Federal nutrition policies and programs. The following section describes the systematic review methodology used to conduct a series of systematic reviews on dietary patterns and health.

Dietary Patterns Systematic Review Project: Roles and Responsibilities

When conducting systematic reviews, NEL staff are assigned to a NEL Project Systematic Review Management Team and work with a Technical Expert Collaborate (TEC), a Stakeholder Group, Abstractors, and Peer Reviewers. A list of the individuals who served these roles is found in the Acknowledgements. The roles and responsibilities of each of these groups and individuals are outlined below.

NEL Systematic Review Management Team
This NEL systematic review project was planned, organized, and guided by a NEL Systematic Review Management Team composed of Federal nutritionists trained in systematic review methodology. This team was led by the Lead Nutritionist of the Nutrition Evidence Library (NEL) and included a Project Manager, Lead Analysts, Technical Advisors, and a Research Librarian. The Project Manager was responsible for leading, planning, organizing, and facilitating the work necessary for execution of the systematic review project. The Lead Analysts led the review of the individual research questions, and the NEL Research Librarian developed and implemented the search strategy for the scientific articles. The Technical Advisors provided advice to help guide the project and served as reviewers of the materials prepared by the Lead Analysts. Specific responsibilities of the NEL Systematic Review Management Team included the following:
  • Facilitated the initial planning and led development of the systematic review project protocol.
  • Directed the execution and quality control of the NEL systematic review project based on input from the TEC and Stakeholders in accordance with the principles and procedures outlined in the NEL systematic review methodology manual.
  • Developed and disseminated products of the review, including this website content, the systematic review report, and peer-reviewed publications.
The NEL Systematic Review Management Team met regularly throughout the systematic review project from conceptualization of the project through completion of the final products. They coordinated regular meetings with the TEC and Stakeholder Groups through conference call and webinar. They also served as the conduit between the TEC and the Stakeholder Group, Abstractors, and Peer Reviewers.

Technical Expert Collaborative
The Technical Expert Collaborative (TEC) consisted of seven national nutrition experts. TEC members assisted the NEL Systematic Review Management Team by reviewing and providing expert feedback to refine systematic review materials. Their expertise was needed to address specific issues related to the topic of dietary patterns and to guide synthesis of the body of evidence to answer the systematic review questions. TEC members guided the systematic review process in the following ways:
  • Reviewed and refined materials drafted by the NEL Systematic Review Management Team, including:
    • Analytical framework and systematic review questions
    • Literature search strategy, including guidance on potential search terms and databases
    • Criteria used to select articles included in the review
    • Lists of included and excluded articles
    • Data extraction plan, including guidance on relevant information that should be extracted from each article and summarized in evidence paragraphs and tables
    • A description of the body of evidence, including evidence worksheets with quality ratings
    • A synthesis of the body of evidence, including identification of themes apparent in the body of evidence
    • Conclusion statements and grades assigned based upon the body of evidence
  • Additionally, the TEC:
    • Provided input on limitations and research recommendations
    • Served as co-authors of manuscript(s) submitted for peer-review publication.
NEL Project Stakeholder Group
Members of the Stakeholder Group included Federal employees who represent end-users of the review and possessed varying perspectives and expertise related to dietary patterns. The Stakeholder Group was instrumental in the initiation of the project to ensure that the products from the reviews would be valuable for informing policies and programs. Specifically, the Stakeholder Group:
  • Assisted in refining and prioritizing systematic review questions
  • Provided input on suggested inclusion and exclusion criteria.
NEL Abstractors
NEL Abstractors are National Service Volunteers from across the United States with advanced degrees in nutrition or a related field. They received training to review individual research articles included in the systematic reviews and rate the methodological rigor (quality) of each study. They extracted evidence from the research articles and posted this information to data fields in evidence worksheet templates in the NEL online portal. The methodological rigor of each included study was assessed using the Research Design and Implementation Checklist. Worksheets prepared by the Abstractors were reviewed by the NEL Systematic Review Management Team and provided a templated presentation of each article to assist the TEC in their review of the evidence.

Peer Reviewers
Peer reviewers were individuals from USDA who reviewed and provided comment on the systematic review products. The peer reviewers provided written input after this draft report was produced. Peer review was sought to ensure that the report provides a transparent and comprehensive description of the review. The NEL Systematic Review Management Team, particularly the Project Manager, coordinated the peer-review and developed responses to comments.

Dietary Patterns Systematic Reviews: Methodology

Research Protocol
The NEL uses a rigorous, transparent, and reproducible methodology that was informed by the Agency for Healthcare Research Quality (AHRQ), the Academy of Nutrition and Dietetics (AND) (formerly the American Dietetic Association), and the US Cochrane Collaboration process. The NEL utilizes a six-step systematic review process to conduct systematic reviews. The steps include:
  1. Systematic review question development
  2. Literature search, screening, and selection
  3. Data extraction and quality assessment
  4. Describing the evidence and evidence synthesis
  5. Developing conclusion statements and grading the evidence
  6. Identifying research recommendations
For a full description of the Methodology, including a summary of each step of the NEL six-step process, , see Chapter 3 of the full report.

Last Updated: 06/02/2014