Vanderbilt nutrition expert appointed to national committee tasked with evaluating new information on energy intake and expenditure.

The Biden administration recently released national strategy to end hunger and increase healthy eating and physical activity by 2030. One of the key directives listed in the report for enhancing nutrition is regular updates to the Dietary Reference Intakes (DRIs), a set of values used by registered dietitians and health care professionals across the United States and Canada to estimate energy requirements that enable individuals and groups to maintain a body weight consistent with good health.

Here, Discoveries speaks with Heidi J. Silver, Ph.D., R.D., an international leader in nutrition science and a research professor in the Division of Gastroenterology, Hepatology, and Nutrition at Vanderbilt University Medical Center, who is currently serving on the 11-member Committee on DRIs for Energy working to publish the first update to the DRIs since 2002.

The committee was assembled in October of 2021 by The National Academies of Sciences, Engineering, and Medicine, and Silver shares what motivated the call to review the DRIs and sheds light on the rigorous process involved in developing new equations and building the contents of the comprehensive report. 

Recognized for Research

Discoveries: The appointment to this committee comes on the heels of another recent honor for your contribution to research, the 2020 Excellence in Research Practice Award from the Academy of Nutrition and Dietetics. Can you tell us more about your interests and work?

Silver: For most of my career, I have focused on investigating how modulating dietary fat and carbohydrate intake in adults with overweight or obesity affects energy balance, body composition, inflammation, insulin resistance, and chronic debilitating disease states.

In particular, my research has revealed the benefits of recognizing that there are different types of fats and carbohydrates, with diverse metabolic effects, and that modulating the type consumed, rather than simply reducing the amount consumed, can have potent outcomes. For example, a recent study from my research group revealed that decreasing the consumption of simple sugars reduces the frequency and severity of the cardinal symptoms of GERD, heartburn and reflux.

The Switch from RDAs to DRIs 

Discoveries: What is the history behind DRIs and how are they used to support decisions regarding nutrition?

Silver: The DRIs are a set of values for energy, macronutrients, and micronutrients that were published between 2000 and 2005 as a series of lengthy reports by The National Academies Press. They represent a major new approach that replace the 1985 RDAs, Recommended Dietary Allowances.

With the DRIs, there are a complete set of quantitative values for energy and each nutrient, separately, that provides an estimate for Americans and Canadians regarding what is the adequate intake (AI), estimated average intake (EAR), recommended daily allowance (RDA), and tolerable upper limit (UL).

The DRIs are used primarily by health care professionals in the U.S. and Canada, but also internationally, to determine requirements for individuals and groups. They’re used on an individual level, for example, when a dietitian works with a patient or client in any clinical or community or private practice setting. They’re also used in group settings when planning meals for large food service systems, like school cafeterias, prisons, the Older Americans Act Nutrition Programs, which includes both home-delivered and congregate meals, and the WIC program. And the DRIs serve as the foundation for federal, state, and local policies, programs, and guidelines.

“It’s important that the DRIs be updated with publication of newer, rigorous evidence, but especially when there’s new data from a changed population demographic.”

New Data on a Changing Population

Discoveries: Given that we’ve gone 20 years without updating the DRIs, what spurred the decision to assemble this committee and review them now?

Silver: There are two key driving forces. For one, over these past 20 years our populations have changed in terms of nutrition and health status. There has been a substantial increase in the prevalence of overweight and obesity, as well as chronic disease states like type 2 diabetes. One question is whether that change in the population demographic means that energy requirements have changed, and thus, the equations to determine energy requirements would need to be updated.

The other consideration is that because two decades of research have passed, there’s a greater body of published evidence to review, especially from well-designed studies that have used the gold standard doubly labeled water method to measure daily energy expenditure. These data will provide applicable information on the energy requirements of the population and population subgroups. It’s important that the DRIs be updated with publication of newer, rigorous evidence, but especially when there’s new data from a changed population demographic.

The Role of the Committee

Discoveries: Can you shed some light on how this process works, how the committee is organizing to review the abundance of information on energy balance?

The committee’s overall task is to assess the evidence from the past 20 years for the human requirements for energy intake and energy expenditure. This includes identifying new evidence on factors that may affect energy requirements – age, sex, body mass, physical activity, and life stage such as pregnancy and lactation. In addition, data will be analyzed to either validate or update the equations used to estimate energy requirements, the EER equations.

The committee is doing a few things simultaneously; reviewing and assessing findings from medical and scientific publications along with analyzing data from the doubly labeled water database. Further, we will identify research gaps and make recommendations. Each of us on the committee has several tasks within these aims.

Discoveries: When do you expect the new report to be published?

Silver: The report that this committee generates will go through a thorough peer-review process as well as by standing committees under The National Academies. It’s a rigorous and iterative process. We expect the report to be ready for publication in spring of 2023.

About the Expert

Heidi J. Silver, Ph.D.

Heidi J. Silver, Ph.D., R.D., is a research professor in the Division of Gastroenterology, Hepatology, and Nutrition and founding director of the Diet, Body Composition and Human Metabolism Core at Vanderbilt University Medical Center. Her research focuses on modulating the macronutrient composition of dietary intakes in patients with obesity to investigate effects on the pathophysiology and outcomes of obesity and diabetes. She also develops imaging protocols to investigate changes in body composition that increase risk for these chronic disease states.