WASHINGTON — A significantly more expansive process leading to the publication every five years of the Dietary Guidelines for Americans has been proposed by a special review committee of the National Academies of Sciences, Engineering, and Medicine.
If the N.A.S. recommendations were adopted, the Dietary Guidelines process would run continuously (currently, relatively little work is done in the two years immediately after publication), a new committee would be established to complement and support the work of the Dietary Guidelines Advisory Committee and a relatively new area of nutrition scientific research, systems approaches, will become important for the future development of eating recommendations.
|Robert M. Russell, professor emeritus, nutrition and medicine, Tufts University, School of Medicine, Boston|
“Redesigning the Process for Establishing the Dietary Guidelines for Americans,” a 229-page report, was prepared by the Committee to Review the Process to Update the Dietary Guidelines for Americans; Food and Nutrition Board; Health and Medicine Division; National Academies of Sciences, Engineering, and Medicine. Chairman of the committee was Robert M. Russell, professor emeritus, nutrition and medicine, Tufts University, School of Medicine, Boston.
The Dietary Guidelines for Americans has been published in a five-year cycle since 1980 jointly by the U.S. Department of Agriculture and the Department of Health and Human Services. The Guidelines are developed based on recommendations from the Dietary Guideline Scientific Advisory Committee, a group of external experts named by the U.S.D.A. and the H.H.S.
Following the publication of the 2015 Guidelines, Congress decided to order a review to improve the advisory committee selection process and to provide greater transparency, eliminate bias, and include committee members with a range of scientific viewpoints.
At the most basic level, concern about the effectiveness of the D.G.A. stems from the small percentage (less than 10%) of Americans who actually follow the Guidelines, an issue that has dogged the recommendations from the time the D.G.A. were introduced in 1980 and especially more recently as problems like obesity have worsened.
The review committee noted a two-part role for the D.G.A.:
- To provide the public “with science-based dietary advice on eating patterns that can help to reduce the risk of developing a chronic disease;”
- Providing guidance for foods to be included in federal nutrition programs, such as the National School Lunch Program, the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) program, and many others.
An earlier report on the D.G.A., published in February 2017, suggested changes in the selection process for the D.G.A.C.
The report recommends changes to the D.G.A. process to reduce and manage sources of bias and conflicts of interest.
Concerns about the D.G.A. increased following publication of the 2015 edition, the review committee said. Discussion about the role of added sugars was a particular lightning rod.
“More than 29,000 public comments were submitted in response to the Scientific Report of the 2015 D.G.A.C. both in support of and against the conclusions made,” the review committee said. “The predominant topic addressed in the public comments was added sugars, with suggestions ranging from overall limitations to ‘a focus on total calories and portion sizes.’ The 2015 D.G.A.C.’s inclusion of sustainability concerns was also controversial. In response to these criticisms, Congress mandated that the National Academies of Sciences, Engineering, and Medicine (the National Academies) evaluate the entire process.”
Also to be reviewed as part of the mandate were how the Nutrition Evidence Library (N.E.L.) is compiled and utilized, how systematic reviews are conducted on longstanding D.G.A. recommendations, including whether scientific studies are included from scientists with a range of viewpoints; and ways the D.G.A. may result in less chronic disease, ensure nutritional sufficiency for all Americans and accommodate a range of individual factors, including age, gender, and metabolic health.
A number of important challenges were identified with regard to the current process. Confusion has arisen over the purpose and the target audience of the D.G.A., the review committee said.
The five-year Guidelines cycle also is flawed, particularly the constraints that come from the two-year Dietary Guidelines Advisory Committee terms. Improvement is needed in the overall process to update the D.G.A.
“The methodological approaches to evaluating the scientific evidence require increased rigor,” the review committee said.
Specifically identified for criticism was the long duration between systematic reviews on a topic under the current system. As a result, recommendations often fail to “keep pace with the emerging science; thus ongoing surveillance of the literature needs to be instituted,” the committee said.
The committee said analytic findings and conclusions “compromise the integrity of the D.G.A. and limit its ability to develop a full body of evidence on a continuous basis over time.”
To enhance the integrity of the Guidelines process and make the recommendations more trustworthy, the review committee identified a number of “values" to pursue:
- Enhance transparency;
- promote diversity of expertise and experience;
- support a deliberative process;
- manage biases and conflicts of interest; and
- adopt state-of-the-art processes and methods.
Judged from the strength of the underlying science used to develop the Dietary Guidelines, the present system is strong, the review committee said. In fact, the process has become “more evidence-based” than ever, thanks to the integration of food pattern modeling into deliberations and because the committee has the ability to conduct systematic reviews.
While supportive of the food pattern modeling that is the basis for developing recommendations, the approach has limited applicability to those who follow different consumption patterns, an issue the committee said needs to be addressed. A more standardized process for identifying nutrients of concern would be helpful.
The review committee also faulted the process for its failure to adapt to changes in food diversity and the increasing prevalence of chronic disease.
The committee advocated the use of “systems approaches” to help clearly define the roles and limitations of diet in reducing chronic disease.
According to the N.I.H., the application of systems-level approaches to the study of nutrition has “helped to elucidate the complex interactions between nutrition and neurobiological, endocrinological, genetic, gut microbial, behavioral and environmental factors, and how these interactions influence metabolic health and the development of chronic diseases such as obesity and type 2 diabetes.” The committee said systems approaches remain in their infancy in the nutrition field.
To explain the application of systems approaches, the committee noted that inadequate intake of iron may result in anemia.
While addressing nutrient deficiency historically has been a focus of dietitian recommendations, the relationship between eating and health is more complicated, the committee said.
“Through years of scientific investigation in nutrition and health, an understanding that there are complex relationships between dietary intake and the risk of developing multifactorial chronic disease has been developing,” the review committee said. “Poor dietary habits have been associated with the increased prevalence of chronic diseases such as type 2 diabetes and cardiovascular disease in the United States. Likewise, poor-quality diets that result in energy imbalance can increase the risk of obesity.”
Regarding the D.G.A. cycle, the review committee said the current approach gives the advisory committee two years to evaluate the science and draw conclusions and then one year to generate a D.G.A. policy report for the government. The other two years in the cycle are a period of “relative inactivity.”
“This National Academies committee believes that using the entire five years for work on the D.G.A. will not only provide the opportunity for a more thorough evaluation of the science, but also allow the D.G.A. process to become more agile, flexible and effective — and address more topics of interest to the general public,” the committee said.
Among the most significant recommendations of the review committee is the creation of a second complementary body beyond the D.G.A.C.
The Dietary Guidelines Planning and Continuity Group (D.G.P.C.G.) would be established to “monitor and curate evidence generation, to identify and prioritize topics for inclusion in the D.G.A. and to provide strategic planning support across D.G.A. cycles,” the review committee said. Their work would be supplemented by efforts from technical expert panels to “provide content and methodological consultation during evaluation of the evidence,” the committee said. Finally, it would be up to the D.G.A.C. to interpret the scientific evidence, draw conclusions and offer recommendations.
As envisioned by the review committee, the planning and continuity group would be populated by federal staff and non-federal experts who would be responsible for generating planning to be submitted to the secretaries of the U.S.D.A. and the H.H.S. that would be aligned with long-term objectives spanning multiple D.G.A. cycles. The group would monitor emerging science on an ongoing basis and would be responsible for identifying and prioritizing topics for the advisory committee to evaluate in future D.G.A. cycles.
“These functions are consistent with the conclusion that not all topics need to be fully reevaluated every five years,” the review committee said. “Strategic planning is needed across D.G.A. cycles.”
With respect to identifying and prioritizing topics, the D.G.P.C.G. would be responsible for disclosing in a brief report the criteria and logic for the list of topics and associated research questions recommended. The D.G.P.C.G. would also help oversee activities to monitor the scientific and public health literature to determine when enough new evidence has been developed on a specific topic.
Supplemental expertise could be secured by the planning and continuity group as needed, the review committee said. For example, the D.G.P.C.G. could commission papers, speakers, consultants, roundtables or subcommittees as appropriate.
Regarding the Nutrition Evidence Library, the committee said the library staff should conduct externally peer-reviewed systematic reviews with input from technical expert panels, perform risk-of-bias assessment of individual studies and assist the D.G.A.C. as needed. The advisory committee would be responsible for synthesizing and interpreting what is generated by the N.E.L. The N.E.L.’s purpose is to conduct such systematic reviews, for the purpose of informing federal nutrition policy and programs.
Executed well, the N.E.L.’s influence could extend beyond how it helps shape the D.G.A.
“The N.E.L. has the opportunity to become a leading evidence source for the nutrition community,” the committee said.
Achieving such a position of respect will require strong training of N.E.L. staff, engagement with and learning from external groups, the invitation of external systematic reviews to evaluate N.E.L.’s methods and an investment in technological infrastructure, the review committee said.
While input from the full range of stakeholders should be welcome, only experts selected by the secretaries of the U.S.D.A. and the H.H.S. and meeting bias and conflict-of-interest criteria ought to be involved in decision-making processes, the review committee said.
To maximize the scientific rigor underpinning the Guidelines, processes and methods employed must be validated and standardized, and data considered must be as up to date as possible, the review committee said. The group said offering specific guidance to groups more narrow than “Americans ages 2 year and older” is crucial for the D.G.A. to gain relevance.“Numerous organizations have developed or endorsed population- or disease-specific guidelines,” the review committee said. “However, the D.G.A. are not designed to adjudicate among them.”