Evaluating the Process to Develop the Dietary Guidelines for Americans, 2020-2025 A Midcourse Report (2022) / Chapter Skim
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4 Analysis of the Scientific Studies Used to Develop the Dietary Guidelines for Americans
4 Analysis of the Scientific Studies Used to Develop the Dietary Guidelines for Americans
Pages 83-102
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From page 83... ...
. In the report Redesigning the Process for Establishing the Dietary Guidelines for Americans (2017 National Academies report)
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From page 84... ...
These include growth, size, and body composition, including overweight and obesity; metabolic syndrome; prediabetes and diabetes mellitus; reduced muscle strength and bone mass; gestational diabetes mellitus; chronic liver disease; cancer; cardiovascular disease; dental health; and food allergy. Using these definitions, 19 of the 34 systematic review questions in the 2020 DGAC Scientific Report were considered as specifically addressing diet-related metabolic diseases (see Appendix G)
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From page 85... ...
c. When existing systematic reviews were used by DGAC, were systematic reviews updated to incorporate the full body of evidence in accord with committee-identified practices?
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From page 86... ...
BOX 4-2 PROSPERO Registry for Systematic Review Protocols PROSPERO is an international registry for systematic reviews with health related outcomes. It comprises a comprehensive database of systematic review protocols, designed to help prevent duplication in protocol design and to serve as a resource for comparing completed reviews against the registered protocol in order to lessen opportunities for reporting bias.
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From page 87... ...
Question 1a: Did question development and systematic review protocols align with committee-identified practices for selecting the body of evidence? Review of evidence The majority of the committee-identified practices that affect the body of evidence are documented in the NESR systematic reviews and the 2020 DGAC Scientific Report (DGAC, 2020)
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From page 88... ...
. The complete systematic review reports included • a question developed with the PICO framework, • a detailed analytical framework, • the final search strategy specifying databases, • the final list of search terms used for each database, • the flow diagram showing the results of the search (number of full texts screened, number of included and excluded studies at each step of the screening and selection process)
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From page 89... ...
. The 2020 DGAC Scientific Report indicated that 16 existing systematic reviews were used (DGAC, 2020)
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From page 90... ...
. The description of the methodology for updating existing systematic reviews described the decision considerations for updating reviews, but it did not fully describe the decision criteria that were used to determine the types of updates that were referenced in the 2020 DGAC Scientific Report (DGAC, 2020)
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From page 91... ...
Conclusions for Committee-Identified Practices The committee concluded that the process to identify questions and create analytical frameworks was implemented, but the external peer review of systematic review protocols and use of existing systematic reviews was only partially implemented. The addition of posting portions of the search protocol for public comment enhanced transparency.
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From page 92... ...
The lack of consistent and thorough documentation of the protocol modifications that led to changes in the studies selected for review decreases transparency and increases the potential for bias. Similarly, the lack of decision guides for determining the need for and type of updates contributed to inconsistent documentation of how existing systematic reviews were updated.
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From page 93... ...
. All systematic reviews included studies that enrolled participants who were healthy and/or at risk for chronic disease, as well as studies that enrolled "some" participants diagnosed with a disease or classified with severe undernutrition or as having underweight, stunting, or obesity (DGAC, 2020)
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From page 94... ...
The committee also found that NESR's overall systematic review criterion to include only countries with a high or very high HDI (DGAC, 2020) may emphasize white European ethnicities and those with higher incomes and underrepresent other ethnicities and those with lower incomes in the data considered in the systematic reviews.
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From page 95... ...
6 Review of evidence The committee's assessment of the DGAC methodology indicated that the NESR analysts supported the DGAC's work to establish the standard inclusion and exclusion criteria to the specific ques 5 Final systematic reviews are available at https://nesr.usda.gov/2020-dietary-guidelines advisory-committee-systematic-reviews (accessed December 1, 2021)
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From page 96... ...
. TABLE 4-2 Two Examples of Nutrition Evidence Systematic Review Overall Search Strategy: Health Status Inclusion and Questions Exclusion Criteria What is the relationship What is the relationship between dietary patterns between types of dietary consumed and risk of fat consumed and risk of cardiovascular disease?
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From page 97... ...
, participants who infants with low birth are healthy and/or weight (<2,500 grams) , who are at risk for and/or infants born a chronic disease small for gestational ageb • Included studies that enroll some subjects with a disease, including those with obesity, or with the health outcome of interest (intermediate or health outcomes)
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From page 98... ...
a Tailoring can include elaborating on how the NESR Overall Search Strategy: Health Status applies to a specific systematic review question OR it can make an exception to the NESR Overall Search Strategy: Health Status criteria. b This tailoring represents an application of the NESR Overall Search Strategy: Health Status in this systematic review.
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From page 99... ...
Question 2d: Were the types of study designs specified appropriate for questions being answered across the systematic reviews prepared for the 2020 DGAC? Review of evidence When the posted systematic review reports were assessed, the committee determined that NESR systematic review searches included the following study designs: RCTs, non-RCTs (including quasiexperimental and controlled before-and-after studies)
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From page 100... ...
The descriptions of the limitations in systematic reviews were not transparent about this because they did not always include information about the diversity of the included study populations. To the questions of the appropriateness of systematic review date ranges and study design, the committee concluded that the appropriate date range was implemented and that the evidence base included in the systematic reviews was current.
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From page 101... ...
The absence of the recommended ongoing surveillance system for published research hampers the ability to determine the need for and the type of updates that will be required. Finally, the exclusion of prevention-intervention research and research from countries not classified with a high HDI may reduce the generalizability of the outcomes of the systematic reviews to the U.S.
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From page 102... ...
In Cochrane handbook for systematic reviews of interventions version 6.2 (updated February 2021)
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