BACKGROUND FOR THE STUDY

The Dietary Reference Intakes (DRIs) are a set of evidence-based nutrient reference values for intakes that include the full range of age, sex, and life stage groups in the United States and Canada. The DRIs are used in planning and assessing diets for generally healthy individuals and groups and also as the basis of nutrition labeling and monitoring the nutritional status of the U.S. and Canadian population and subpopulations (for both inadequate and excess nutrient intakes). The DRIs underpin nutrition guidance by providing a scientific basis for developing dietary guidelines and federally sponsored nutrition education programs. They also support meal standards for federal nutrition assistance programs and the U.S. military services.

Beginning in 1994, the United States and Canada cosponsored developing and publishing a set of nutrient-based DRI values. The process for deriving these has evolved; the current approach includes the following:

• A review of current reference intake values to determine the need for updating on the basis of available sufficient new evidence;
• The inclusion of the concept of a chronic disease risk reduction (CDRR) value, where sufficient data for efficacy and safety exist;
• A reference value format that includes two core reference values: the Estimated Average Requirement (EAR), and the Tolerable Upper Intake Level (UL).

The Recommended Dietary Allowance (RDA) is derived from the EAR. The RDA and the UL represent the bounds of a “safe level of intake.” For some nutrients, the available evidence does not allow for an EAR and thus an RDA to be set. As a result, two additional reference values were devised to estimate intake needs in this situation—the Adequate Intake (AI) and, for macronutrients, the Acceptable Macronutrient Distribution Range. The Estimated Energy Requirement was developed to estimate energy needs to maintain energy balance.

The Institute of Medicine of the National Academies of Sciences, Engineering, and Medicine (the National Academies) published six DRI reports between 1997 and 2005 on 29 vitamins and minerals, as well as macronutrients and other food components, such as energy and fiber. The DRI approach has evolved based on lessons learned from the previous review and adoption of more rigorous methodologies. The process now includes nutrient- and outcome-specific systematic reviews and meta-analyses. A systematic review was first applied to re-review DRIs for calcium and vitamin D (IOM, 2011). A new DRI value, the CDRR, was derived in the DRI re-review for sodium and potassium (NASEM, 2019).

New DRI reviews now require systematic reviews and consideration of chronic disease endpoints. The primary evidence to be used as a data resource is derived from systematic reviews and meta-analyses that assess the evidence for relationships between specific nutrients and relevant health outcomes in support of DRI development; both are conducted as a separate activity from the DRI review to avoid conflicts of interest or introducing bias. Since 1997, only two pairs of nutrients (calcium and vitamin D; sodium and potassium) have been reexamined and updated. It is unlikely that all nutrients will have the level of evidence required to undergo a full DRI review, but assessment and initial prioritization of any new evidence available is needed to determine whether a full reexamination is warranted.

In 2016, four members of the Food and Nutrition Board of the National Academies published an evidence-based methodology, termed “evidence scanning,” which was used to determine whether new relevant information existed for specific nutrients that could be used for a future DRI review (Brannon et al., 2016). They identified thiamin and phosphorous as candidate nutrients to serve as case studies in developing a framework for evidence scanning. For a given nutrient, the findings of the evidence scan serve as a starting point for a systematic review, thereby reducing the preparatory work on a new systematic review and saving the federal agencies time and money on each review. The thiamin and phosphorus case studies laid the groundwork for the methodology used in this report.

JUSTIFICATION

The Federal DRI Steering Committee is interested in adapting the evidence scan methodology to develop a framework for evidence scanning candidate nutrients to identify those that may have new or significant data relevant to future DRI reviews. The goal of this evidence scan was not to conduct a formal systematic review but to thoroughly scan the peer-reviewed published literature to determine the status of evidence on riboflavin as a candidate nutrient for a DRI review. The framework and methodology in this report is intended to serve as a model for future evidence scans of other nutrients of interest. Collectively, these evidence scans will inform the decision-making process of identifying and prioritizing nutrients for future DRI reviews.

THE COMMITTEE'S TASK AND APPROACH

The U.S. Department of Agriculture, Agricultural Research Service and the U.S. Department of Health and Human Services, Food and Drug Administration, Center for Food Safety and Applied Nutrition requested that the National Academies carry out an evidence scan on new and emerging evidence on riboflavin that could be used to support a DRI review (see Box 1-1).

BOX 1-1

Statement of Task.

The National Academies' Health and Medicine Division established a committee with expertise in epidemiology; public health; biochemistry and physiology related to riboflavin; nutrient requirements by age group, including infants; the DRI process and framework; and systematic review methodology. The committee held an open meeting with subject-matter experts (see Appendix B) and worked in closed session and by conference calls to deliberate.

ORGANIZATION OF THE REPORT

This report is organized into four chapters. This chapter describes the background for the study, the Statement of Task, and the study strategy. Chapter 2 provides the search strategy, including the prespecified criteria for assessing relevant evidence and a flow diagram to illustrate the evidence screening and review processes. Chapter 3 presents a table of the results and the committee's assessment of relevant evidence. Chapter 4 provides the committee's discussion of the findings and perspective on future directions.

REFERENCES

• Brannon PM, Weaver CM, Anderson CA, Donovan SM, Murphy SP, Yaktine AL. Scanning for new evidence to prioritize updates to the Dietary Reference Intakes: Case studies for thiamin and phosphorus. American Journal of Clinical Nutrition. 2016;104(5):1366–1377. [PubMed: 27733406]
• IOM (Institute of Medicine). Dietary Reference Intakes for calcium and vitamin D. Washington, DC: The National Academies Press; 2011. [PubMed: 21796828]
• NASEM (National Academies of Sciences, Engineering, and Medicine). Dietary Reference Intakes for sodium and potassium. Washington, DC: The National Academies Press; 2019. [PubMed: 30844154]