Although the process used to develop the Dietary Guidelines for Americans (DGA) has become more evidence based since its inception more than 30 years ago, it is not currently positioned to effectively adapt to changes such as food diversity and chronic disease prevalence while also ensuring the integrity of the process, according to a new congressionally mandated report from the National Academies of Sciences, Engineering & Medicine (NAS).
The U.S. Department of Agriculture and U.S. Department of Health & Human Services (HHS) should comprehensively redesign the process for updating the DGA to improve transparency, promote the diversity of expertise and experience, support a deliberative process, foster independence in decision-making and strengthen scientific rigor, NAS said.
The DGA provides nutritional and dietary information to promote health and prevent chronic disease. Reviewed and updated every five years, the guidelines underpin all federal nutrition policies and programs, such as the National School Lunch Program and the Special Supplemental Nutrition Program for Women, Infants & Children.
The process for updating the DGA begins with an independent evaluation of the scientific evidence by the Dietary Guidelines Advisory Committee (DGAC) -- a group selected and convened by USDA and HHS. The conclusions and recommendations of the DGAC are then submitted to the secretaries of USDA and HHS in the form of a scientific report. The DGAC report is advisory only and does not constitute draft policy, although it does serve as the scientific evidence base for updating the subsequent edition of the DGA. The guidelines themselves are then developed by USDA and HHS.
“The Dietary Guidelines for Americans have the promise to empower Americans to make informed decisions about what and how much they eat to improve health and reduce the risk of chronic disease,” said Robert Russell, professor emeritus of nutrition and medicine at Tufts University and chair of the NAS committee that conducted the study and wrote the report. “Despite this potential, fewer than 10% of Americans consume a diet fully consistent with the DGA. A more trustworthy, agile and effective process can improve the relevance and usefulness of the DGA, which may ultimately improve adherence to the guidelines. The process to update the DGA should be redesigned to increase transparency and allow for the appropriate expertise and time to focus on each step of the process, which can be achieved by reallocating the steps to a balanced and expanded set of multidisciplinary experts.”
The juxtaposition of the five-year DGA cycle and the two-year term for each DGAC constrains the overall system, including the time available to complete necessary tasks, the report says. The DGAC conducts all tasks associated with scientific review, limiting opportunities for a truly deliberative process with the nutrition community, technical experts and the public.
The report recommends redistributing the tasks of the DGAC to three separate groups with more targeted expertise in order to leverage the five-year cycle more effectively: (1) a Dietary Guidelines Planning & Continuity Group to monitor for and curate new evidence, identify and prioritize topics for inclusion in the DGA and provide strategic planning support across DGA cycles; (2) technical expert panels to provide content and methodological consultation during evidence evaluation, and (3) a Dietary Guidelines Scientific Advisory Committee to interpret the scientific evidence and draw conclusions.
The report recommends that the secretaries of USDA and HHS carry out several other actions in a number of areas as part of the process redesign, including:
* Enhance transparency. A clear explanation should be given when the DGA omits or accepts only parts of conclusions from the DGAC scientific report. Enhancing transparency -- for example, by appropriately balancing individual biases and conflicts of interest -- is vital to engendering public trust in the process as well as providing assurance that decisions were made free of undue influences. Opportunities for participation and engagement from stakeholders -- including the public, academia and researchers, advocacy groups, professional organizations, the food sector and federal agencies -- should be enhanced, as it is critical to fostering diversity and increasing trustworthiness of the process.
* Strengthen the evidence base. Methodological approaches and scientific rigor for evaluating the evidence should be strengthened by using validated, standardized processes and methods with the most up-to-date data. It is critical that, for example, the Nutrition Evidence Library is aligned with best practices for conducting systematic reviews and uses appropriate methods.
* Advance the methods used. Processes and actions should be based on the best available evidence, requiring that the analyses used be continuously improved and advanced. Food pattern modeling should better reflect complex interactions, variability in food composition and consumption and the range of possible healthful diets. In addition, standardizing the methods and criteria for establishing “nutrients of concern” would lead to consistent development of quantitative thresholds of inadequacy or excess. To help more clearly define the roles and limitations of diet in reducing chronic disease risk, the report recommends a systems science approach that accounts for complex relationships, for example, biological, behavioral, social and environmental interactions and pathways.
In terms of their scope, future guidelines should focus on the general public across the entire life span, not just healthy Americans ages two years and older, the report says. Given the range in health status and the prevalence of chronic diseases in the population, as well as the importance of nutrition to pregnant women and children from birth to 24 months, it is essential that future DGAs be developed for all Americans whose health could benefit by improving diet. The breadth and content of each DGAC report could vary, because not all topics may require a detailed review every five years; only those topics with enough new data to generate a full review would be considered for in-depth evaluation in the next DGA cycle.
The Nutrition Coalition applauded the report. They said a crucial finding of the report is that the current DGA process for reviewing the science falls short of meeting the "best practices for conducting systematic reviews," and that "methodological approaches and scientific rigor for evaluating the scientific evidence" need to "be strengthened." The report states, "To develop a trustworthy DGA, the process needs to be redesigned."
"These guidelines don't operate in a vacuum. Flaws in the DGA process are the major force shaping the U.S. food supply, and they drive dietary advice by all healthcare practitioners as well as all federal nutrition policy – from school lunches to food stamps to even the meals served to our active duty military service members,” said Jeff Volek, scientific advisory council member for the Nutrition Coalition and professor at The Ohio State University. “For years, we've been told that the Dietary Guidelines are the gold standard and that if Americans are obese and diabetic, it must be their fault. This report confirms that this is not the case."
The first NAS report of this study, released in February, recommended ways to improve the selection process for the DGAC to provide more transparency, manage bias and conflicts of interest and include committee members with a range of viewpoints.