Understanding the Scientific Process that Informs the Dietary Guidelines for Americans

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The Dietary Guidelines translates the current body of nutrition science into sound food-based guidance for ages 2 and older to promote health and help prevent disease. The Dietary Guidelines is developed through a process that has become increasingly more robust and transparent with each edition.

Review of Current Scientific Evidence

The Departments of Health and Human Services (HHS) and Agriculture (USDA) are required by the National Nutrition Monitoring and Related Research Act of 1990 to jointly publish the Dietary Guidelines for Americans every five years. The development of the 2015-2020 Dietary Guidelines for Americans started with a review of the current scientific evidence.

The Federal Government uses federal advisory committees to seek sound external scientific advice to inform decision making. For this reason, the 2015 Dietary Guidelines Advisory Committee (Advisory Committee) was formed in accordance with Federal Advisory Committee Act rules. The Advisory Committee included prestigious researchers and scientists in the fields of nutrition, health, and medicine who met in public meetings from June 2013 to December 2014 to discuss findings and develop recommendations to the Government for consideration in developing the 2015-2020 Dietary Guidelines. The public was invited to submit written comments to the Advisory Committee throughout the entirety of its work as well as oral comments at a public meeting.

The 2015 Advisory Committee was charged with reviewing the 2010 Dietary Guidelines for Americans to determine topics for which new scientific evidence is likely available and to review that evidence to inform the development of the 2015-2020 edition. As with the 2010 Dietary Guidelines Advisory Committee, the 2015 Advisory Committee used four methods to examine the scientific evidence on the relationships between diet and health:

  • Original systematic reviews. Systematic reviews are the gold standard for informing clinical practice guidelines and public health policies worldwide. The Advisory Committee used the Nutrition Evidence Library (NEL) to complete original systematic reviews to identify specific research questions, search the scientific literature for relevant articles, assess the quality of each included article, and summarize, analyze, and grade the evidence presented in the articles.
  • Review of existing systematic reviews, meta-analyses, and reports by federal agencies or leading scientific organizations. For some topics, an original systematic review was not necessary because an existing high-quality review or report already addressed the topic under consideration. For these areas, existing reviews were evaluated for quality to ensure that they rigorous and held to the same high standards as the reviews conducted through the NEL.
  • Data analyses. The Advisory Committee used existing and new data analyses of national data from federal agencies to answer questions about chronic disease rates, food and nutrient intakes, and nutrient content of foods.
  • Food pattern modeling analyses. The Advisory Committee estimated the effect of possible changes in types or amounts of foods on diet quality through food pattern modeling analyses. The modeling analyses informed the Committee’s recommendations on specific topics and kept recommendations grounded within healthy eating patterns.

The work of the Advisory Committee was submitted to the Secretaries of HHS and USDA in the Scientific Report of the 2015 Dietary Guidelines Advisory Committee, and made available for public comment.

Learn more about the work of the Advisory Committee.

Development of the Dietary Guidelines for Americans

The Dietary Guidelines for Americans is written by a group of experts from both HHS and USDA who have extensive knowledge of nutrition and health science, Federal nutrition recommendations, and program implementation. In addition to the recommendations from the Advisory Committee, HHS and USDA attained input from nutrition and medical experts and comments from the public to develop the 2015-2020 Dietary Guidelines for Americans. Similar to previous editions, this edition builds on the preceding edition, with revisions informed by the Advisory Committee’s scientific report and consideration of public and federal agency comments received through three methods:

  • Public comments. The public was invited to submit written comments throughout the Advisory Committee’s work and on its Advisory Report. Comments on the Advisory Report were considered during the development of the Dietary Guidelines, with an emphasis on comments with scientific justification.
  • Peer-review. Non-federal experts independently conducted a confidential review of a draft of the 2015-2020 Dietary Guidelines for Americans for clarity and to ensure that the evidence from the Advisory Committee’s report was accurately translated into guidelines.
  • Federal agency review. Federal agencies with scientific expertise in nutrition and health, such as the Centers for Disease Control and Prevention (CDC), the National Institutes of Health (NIH), the Food and Drug Administration (FDA), and the USDA Food Safety and Inspection Service (FSIS) provided comments on the Advisory Committee’s report, served as technical reviewers of the document, and were consulted throughout the guideline development process. The final 2015-2020 Dietary Guidelines were reviewed and approved by agencies across both Departments and, ultimately, by the Secretaries of HHS and USDA.

Learn more about the development of the 2015-2020 Dietary Guidelines.

Implementing the Dietary Guidelines for Americans

The Dietary Guidelines provides guidance to federal food and nutrition programs and inform public health initiatives and health policies which impact millions of people each day. It provides a foundation for Federal programs such as USDA’s National School Lunch Program and School Breakfast Program and the Special Supplemental Nutrition Program for Women, Infants and Children (WIC), HHS’s Older Americans Act Nutrition Services programs and Head Start, as well as healthy education campaigns by CDC, NIH and FDA. The Dietary Guidelines also impacts public health initiatives and activities across the Nation. For example, health professionals rely on the Dietary Guidelines for current, evidence-based nutrition information that can be used to improve eating behaviors in the populations they serve; academic institutions, national public health organizations, advocacy groups, and the media refer to the Dietary Guidelines when translating scientific information for the general public; and the food industry also uses the Dietary Guidelines in planning food reformulations and when marketing and promoting products to consumers.

Learn more about how the Dietary Guidelines is implemented.

Frequently Asked Questions About the Science Behind the Guidelines

Q: Why is the Dietary Guidelines updated every five years? Does the science change that frequently?

  • The Dietary Guidelines is an investment in the health of all Americans. It is our responsibility to the American public to ensure that advancements in scientific understanding about the role of nutrition in health like these are incorporated into the Dietary Guidelines on a regular basis. That is why the Dietary Guidelines is updated every five years – and this is also required by the National Nutrition Monitoring and Related Research Act of 1990
  • For each edition, the process that informs the Dietary Guidelines has become increasingly robust and transparent. We know more about the relationship between nutrition and health each time we develop a new edition of the Dietary Guidelines.
  • For example, guidance has evolved based on what we now know about sugar and caffeine since the last edition of the guidelines in 2010. We are now able to offer more concise guidance on topics like sodium, cholesterol and saturated fats, and alcohol, and we have been able to validate what we know about topics like vegetables and fruits.

Q: Throughout the Dietary Guidelines, you refer to strong, moderate, and limited evidence to support recommendations. Can you explain what this means?

Throughout, the 2015-2020 edition of the Dietary Guidelines notes the strength of evidence supporting its recommendations.

  • Strong evidence reflects a large, high-quality, and/or consistent body of evidence. There is a high level of certainty that the evidence is relevant to the population of interest, and additional studies are unlikely to change conclusions derived from this evidence.
  • Moderate evidence reflects sufficient evidence to draw conclusions. The level of certainty may be restricted by certain limitations in the evidence, such as the amount of evidence available, inconsistencies in findings, or limitations in methodology or generalizability.
  • Limited evidence reflects either a small number of studies, studies of weak design or with inconsistent results, and/or limitations on the generalizability of the findings.

Q: Do you have any evidence that the Dietary Guidelines works?

  • The Dietary Guidelines is focused on disease prevention rather than disease treatment. The Guidelines was originally developed because of increases in disease rates.
  • Research shows that diets that align most closely with the Dietary Guidelines – as indicated by the Healthy Eating Index (HEI) – are associated with a 15-22% reduction in the risk for both onset of and death from cardiovascular disease, cancer, and type 2 diabetes.
  • According to a recent study by Harvard researchers, from 1999 – 2012, an estimated 1.1 million premature deaths were prevented through improvements in diet quality. Diet quality also resulted in 8.6 percent fewer cardiovascular disease cases and 12.6 percent fewer type 2 diabetes cases.
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