Federal advice to the public on nutrition and diet is intended to reflect the state of the science and deliver the most reliable recommendations according to the best available evidence. This advice, presented in the Dietary Guidelines for Americans (DGA), underpins all federal nutrition policies and programs and is updated every 5 years. The process to create the guidelines is not a simple one, and it changes as the science evolves. Much has been accomplished to improve how the science is evaluated and translated into the DGA, such as the establishment of the Nutrition Evidence Library (NEL) to conduct evidence-based reviews. The target population for the DGA will also expand in the 2020–2025 edition to include recommendations for all Americans by including pregnant women and children from birth to 2 years.
Despite the many accomplishments, recent challenges to federal nutrition guidance prompted Congress to question the process by which food and nutrition guidance is developed (Conaway, 2015; Hartzler et al., 2015; U.S. Congress, House of Representatives, Committee on Agriculture, 2015). To address these questions, Congress mandated a review of the entire process used to develop the DGA.1
1 Consolidated Appropriations Act, 2016. Public Law 114-113, 114th Cong. (December 18, 2015), 129 Stat. 2280–2281.
The DGA provide nutritional and dietary information to promote health and prevent disease (HHS/USDA, 2015). To help Americans make healthful food choices, the U.S. Department of Agriculture (USDA) and the U.S. Department of Health and Human Services (HHS) jointly review and update the guidelines every 5 years to reflect “the preponderance of the scientific and medical knowledge which is current at the time the report is prepared.”2 The process to develop the guidelines has evolved over time in an effort to develop gold-standard guidelines. The guidelines are formed through a multistep process developed by USDA and HHS. USDA and HHS receive input from a scientific advisory committee, other federal agencies, and the public (see Figure 1-1).
While the term DGA has been used generally to refer to the report and the specific guidelines, for the purpose of clarity, more specific terminology is used throughout this National Academies of Sciences, Engineering, and Medicine (the National Academies) report (see Box 1-1).
Since the first edition in 1980, the guidelines have served as the basis for federal nutrition policies and nutrition assistance programs, as well as nutrition education programs.3Box 1-2 provides examples of how the DGA are used at various levels of government.
Overview of the Process to Update the DGA
First, a charter is filed with Congress to establish a scientific advisory committee, known as the Dietary Guidelines Advisory Committee (DGAC). The advisory committee comprises nationally recognized experts responsible for independently evaluating the scientific evidence to inform revisions to the current policy or suggest new guidance. Its conclusions are submitted to the secretaries of USDA and HHS as the Scientific Report of the Dietary Guidelines Advisory Committee. The DGAC’s report
2 National Nutrition Monitoring and Related Research Act of 1990, Public Law 101-445, 101st Cong. (October 22, 1990), 7 U.S.C. 5341, 104 Stat. 1042–1044. The departments are required to act within the National Nutrition Monitoring and Related Research Act of 1990, Agricultural Act of 2014, Federal Advisory Committee Act of 1972, and the Consolidated Appropriations Act of 2001 (Data Quality Act) (USDA/HHS, 2016).
3 Federal nutrition assistance and education programs include Child and Adult Care Food Program; Commodity Supplemental Food Program; Food Distribution Program on Indian Reservations; Fresh Fruit and Vegetable Program; National School Lunch Program; Nutrition Services Incentive Program; Nutrition Standards for School Meals; School Breakfast Program; Serving Up MyPlate; SNAP-Ed; Special Milk Program; Special Supplemental Nutrition Program for Women, Infants, and Children (WIC); Summer Food Service Program; Supplemental Nutrition Assistance Program; Team Nutrition; The Emergency Food Assistance Program; USDA Foods–School Resources; and WIC Works.
serves as the scientific basis for the DGA, but its conclusions are advisory in nature only; the scientific report does not constitute draft policy.
The secretaries then solicit comments on the DGAC Scientific Report from the public and other federal agencies. Next, a federal writing team—consisting of staff from USDA and HHS—collects, assesses, and reviews these comments as it develops the next edition of the DGA Policy Report. The draft DGA Policy Report undergoes a series of internal departmental reviews, including reviews by more than 100 subject-matter experts from the federal government, and revisions prior to approval by the secretaries. Finally, the DGA Policy Report is published publicly with the primary
audience being health professionals who then implement the guidelines through programs supported by federal, state, and local governments (see Appendix D for a list of the DGA recommendations since 1980).
Criticisms of the 2015–2020 DGA
When the Scientific Report of the 2015 Dietary Guidelines Advisory Committee was released in February 2015, more than 29,000 written public comments were submitted. In contrast, approximately 2,000 comments were received in response to the 2010 DGAC Scientific Report (U.S. Congress, House of Representatives, Committee on Agriculture, 2015). Of the statements received in 2015, approximately 21,000 submissions were form letters or petitions. Form letters were the major type of submission, comprising greater than 70 percent of all comments; 33 unique form letters were received. Approximately 187,000 signatures were received from 47 petitions. Critiques of the report itself and the process used—both in support of and against the conclusions—were raised for a wide range of topics. The predominant topic addressed was added sugars. Some remarks suggested a limitation on added sugars, while others promoted “a focus on total calories or portion sizes” (HHS, 2015). The issue of sustainability was also widely addressed and was the subject of a large majority of form letter submissions, most of which supported its inclusion. Many statements also referred to lean meat, largely questioning its lack of inclusion in the scientific report as part of a healthful diet, but others referenced concerns about cholesterol and saturated fat associated with meat consumption. Plant-based diets were another frequently identified topic, with comments both in favor of and against a shift to a more plant-based diet. A variety of other comments were received, such as suggestions to focus on a specific micronutrient or macronutrient, making the guidelines easier to apply, and specific critiques about the processes used by both the DGAC and the method it used to evaluate the science (HHS, 2015).
In part because of the large number of comments, Congress raised questions about the scope of the 2015 DGAC, stating that the DGAC did not have the expertise, evidence, or charter to comment on topics such as sustainable diets and tax policy (Conaway, 2015; Hartzler et al., 2015). Others raised questions regarding the evidence used and the comprehensiveness of the literature reviewed (Dabrowska, 2016; Heimowitz, 2016; Hentges, 2016; Mozzaffarian, 2016; Teicholz, 2015). Following an examination of these public comments, the House Committee on Agriculture held a hearing where the secretaries of USDA and HHS were asked to clarify, among other things, that the DGAC Scientific Report was based in science and that sustainability concerns were outside the scope of the DGAC. Congress also raised questions about the process to develop the DGA, asking whether the process could be trusted by the American people, and demanding that the DGA be developed in a transparent and objective manner (U.S. Congress, House of Representatives, Committee on Agriculture, 2015).
After the release of the Dietary Guidelines for Americans 2015–2020: Eighth Edition in January 2016, USDA invited 40 stakeholders to voice support or concern for the process of developing the DGA. Ten professional organizations were represented, as well as 18 members of industry and 12 individuals with various background and professional associations. A summary of the comments received related to the composition and the selection process of the DGAC can be found in this National Academies committee’s first report (NASEM, 2017). Comments from the listening session were made both in favor of and against the current processes used to develop the DGA Policy Report. Frequently discussed topics included the processes used to create the DGA Policy Report and the DGAC Scientific Report, as well as how evidence was assessed for the scientific report. Also commonly mentioned was the timing of when research questions are developed, as well as the suggestion to provide more opportunities to comment on the questions for the DGAC to consider before it conducts its work. Commenters discussed the periodicity of the DGA, with some arguing for more frequent editions and others suggesting less frequent revisions.
Greater transparency into the process to translate the DGAC Scientific Report into the DGA Policy Report was also raised as a point for potential improvement. The potential conflict of interest USDA might have in managing and supporting the DGA given its role in supporting U.S. agriculture, as well as potential influence from Congress and the food sector, was also raised. Others suggested that USDA and HHS might be reluctant to make changes that would contradict previous guidelines. Statements were also presented regarding the literature review process—approximately half were positive—with others suggesting that the DGAC evaluate how it interprets and considers different study types. Many presenters also stated their support for the NEL process as being evidence-based, transparent, and held to rigorous scientific standards. Others critiqued the NEL, challenging its comprehensiveness, the DGAC’s inconsistent use of the NEL, and lack of public access to the NEL’s work throughout the DGAC process. Numerous suggestions were also made about measuring the effectiveness of the DGA and developing education programs to strengthen the public health impact of the DGA. Calls were also made to clarify the target audience and the scope of both the DGA and the DGAC (USDA, 2016a).
In response to concerns raised about the process to produce the 2015–2020 DGA Policy Report, Congress directed USDA to engage with the
National Academies to appoint a committee to conduct a comprehensive evaluation of the processes used to establish the DGA (see Box 1-3 for the Statement of Task).
Importantly, this National Academies committee is not evaluating the substance of the guidelines or their use; its charge is to assess the process. As such, the findings in this report should not be considered as judgments about the quality of prior DGA or DGAC reports. The questions in the Statement of Task are divided and addressed in two reports. This National Academies committee’s first report responded to the first part of the task for the purpose of informing the 2020 cycle. That report recommends a number of ways to enhance transparency in the selection process for DGAC members, including identifying and managing biases and conflicts of interest (NASEM, 2017) (see Box 1-4).
The conclusions and recommendations contained herein respond to parts 2–4 in the Statement of Task. Although most of the evidence and analysis related to the first question was discussed in the first report, some related issues are relevant to the present report and therefore are included. For example, the Agricultural Act of 2014 requested that the DGA be expanded to include people across the life span, adding guidance for pregnant women and children from birth to 24 months. Because this expansion may significantly affect the DGA—and by extension the DGAC—it affects the considerations for how the DGAC is composed and is thus discussed in this report. As part of this overall, comprehensive review of the process to update the DGA, additional findings and recommendations about the selection process are made. Additionally, some of the questions relevant to the selection process, such as how specific priority areas are determined and how the DGAC’s conclusions are considered in the DGA Policy Report, are also explored here.
The National Academies appointed 14 members to the Committee to Review the Process to Update the Dietary Guidelines for Americans to respond to a congressional request.4 For this second report—to assess the rigor of the NEL, how systematic reviews are conducted on longstanding DGA recommendations, and how the DGA can better prevent chronic disease and ensure nutritional sufficiency for all Americans—this National Academies committee met in person twice and convened in closed session three times via webinar. Its discussions also benefited from engaging with the public; one in-person public comment session was
4 Consolidated Appropriations Act, 2016, Public Law 114-113, 114th Cong. (December 18, 2015), 129 Stat. 2280–2281.
held, where members of the public were invited to address the committee. Those who made a statement included representatives of industry, professional organizations, advocacy groups, and individuals (see Appendix B). Additionally, the committee solicited written input from the public about what it believed to be major challenges to implementing the DGA and the greatest opportunities for the DGA to better prevent chronic disease and ensure nutritional sufficiency. Statements and comments were received by this National Academies committee from industry representatives, professional organizations, and interested individuals. All statements were considered over the course of the committee’s deliberations.
Organization of This Report
This report consists of two parts to facilitate understanding of this National Academies committee’s vision and recommendations for an
improved process to update the DGA, particularly for those readers who are already familiar with the details of the current process. Part I of this report, inclusive of Chapters 2, 3, and 4, presents this National Academies committee’s ideas and recommendations for how the DGA can better serve the American public in response to the Statement of Task. It describes a brief overview of the process to develop the DGA, the main findings and conclusions from this National Academies committee’s evaluation, and recommendations. Chapter 2 describes this National Academies committee’s vision for the roles and purposes of the DGA. Chapter 3 suggests a proposed model for the DGA. Chapter 4 provides recommendations for enhancing the science underlying the DGA.
Part II describes the current process in greater detail and this National Academies committee’s analysis of the process and its evaluation of the evidence. Part II provides the basis for the conclusions and recommendations discussed in Part I. Chapter 5 describes and evaluates the current process for developing the DGA and presents findings that serve as the basis for the suggestions and recommendations in Chapter 3. In Chapter 5, this National Academies committee found that (1) the purposes and audiences of the DGA have not been consistently interpreted over time, (2) the cycle time and complexity of tasks constrain the current DGAC process, and (3) the current process is not as transparent or participatory as it could be.
Chapter 6 examines the types of analyses used to update the 2015–2020 DGA and provides assessments upon which recommendations are made in response to Statement of Task questions “How is the Nutrition Evidence Library compiled and utilized, including whether NEL reviews and other systematic reviews and data analysis are conducted according to rigorous and objective scientific standards?” and “How are systematic reviews conducted on long-standing DGA recommendations, including whether scientific studies are included from scientists with a range of viewpoints?” This chapter asserts that the types of analyses used to update the 2015–2020 DGA—(1) original systematic reviews; (2) existing systematic reviews, meta-analyses, and reports; (3) food pattern modeling; and (4) descriptive data analyses—provide important inputs into the DGA process. This National Academies committee found that the NEL process for conducting original systematic reviews is thorough but has not been updated to reflect recent advances in systematic review methodology. Additionally, the roles of the DGAC and NEL staff have not been clearly delineated in the DGA process. Although food pattern modeling has been conducted according to appropriate methods, it has been limited by the food groupings, assumptions, and constraints inherent in the models. Finally, descriptive data analyses conform to current approaches, but the DGAC’s analyses can be limited by the availability of current data.
Chapter 7 reviews how previous DGACs considered nutritional adequacy and chronic disease, and it builds the basis for responding to the Statement of Task question “How can the DGA better prevent chronic disease, ensure nutritional sufficiency for all Americans, and accommodate a range of individual factors, including age, gender, and metabolic health?” This National Academies committee found that the process by which nutrients of concern are identified has yet to be standardized across DGA cycles. DGACs have yet to use an analytical framework to guide topic selection, synthesis, and interpretation of the evidence on topics of the relationship of diet, health, and chronic disease.
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