5.1: Development of Nutrient Reference Values (8a.1)

The first set of nutrient reference values (NRVs) was produced by the Technical Commission on Nutrition, League of Nations, (1938). The recom­men­dations of this Commission formed the basis for the first Canadian Dietary Standard compiled by the Canadian Council on Nutrition (1940). The United States Food and Nutrition Board (in 1943) prepared the first U.S. Recom­mended Dietary Allowances (RDAs) for protein, energy, and eight vitamins and minerals. This was followed by periodic revisions of the U.S RDAs and a number of joint publications by the World Health Organization / Food and Agriculture Organization on recom­men­dations for different groups of nutrients (FAO/WHO, 1974; FAO/WHO, 1988). By 1989, the U.S RDAs included 25 vitamins and minerals in addition to protein and energy.

Until this time, these reports provided a single estimate of require­ments (i.e., the RDA or equivalent) that was sufficient to meet the needs of almost all indi­viduals in a specific life-stage group. Nevertheless, despite being set for indi­viduals, the RDAs were being applied to pop­ula­tion data and used for many different purposes. This misuse of the RDA led to the development of new approaches to address multiple users and needs. The first country to adopt a framework that embraced three nutrient reference levels was the United Kingdom(COMA,1991) (Section 8a.4). This was followed by the release by the U.S. Food and Nutrition Board (FNB) of a new paradigm of Dietary Reference Intakes (DRIs)(National Academic Press, 2000). Their approach, developed jointly by the U.S. and Canada, also provided multiple reference levels for each nutrient and included for the first time an upper intake value (UL) as well as the concept of reducing the risk of chronic diseases

This new multi-level approach was soon adopted with some modifications by other authoritative bodies worldwide, including in China; Korea and Southeast Asia; Germany, Austria, Switzerland; Australia and New Zealand; and Mexico. Most established an Estimated Average Requirement (EAR) and a RDA (or equivalent) at two standard deviations above the EAR, although the exact terms used differed. Some authorities also included a Tolerable Upper Intake Level (UL) for certain nutrients, and in many cases, a safe or ade­quate intake value (or range) when insufficient information was available to set an EAR (King et al., 2007).

One of the latest developments includes the intro­duction of a systematic review process to identify data relevant to the derivation of NRVs. This initiative was introduced in 2007 by the EURopean micronutrient RECommendations Aligned (EURRECA) Network of Excellence (NoE) (Dhonukshe-Rutten et al., 2013), and used in the U.S. and Canada for the first time for the revision of the NRVs for vitamin D and calcium (IOM, 2011). More recently, efforts have been made to overcome some of the challenges encountered when setting nutrient reference values for chronic disease prevention; these efforts are on-going (Yetley et al., 2017).

There is now considerable interest in providing a framework for harmonizing the process to derive NRVs that can be applied across countries and a variety of pop­ula­tion sub­groups, while taking into account culturally and context-specific food choices and dietary patterns. This international harmonizing initiative first began in 2005 with the development and publication of several background review papers and a consensus report on “Harmonization of nutrient intake values” (King and Garza, 2007). The first harmo­nization initiative was followed a decade later with an inter­national workshop convened in 2017 by the National Academies of Sciences, Engineering, and Medicine (NASEM) in partnership with WHO and FAO to explore the evidence for achieving global harmonization of method­ological approaches to derive NIVs across countries; see NASEM (2018a) for the report of the workshop proceedings. (Table 8a.1). At this workshop, the term Nutrient Reference Values (NRVs) was adopted to describe collectively the nutrient intake recom­men­dations and is analogous to terms currently in use such as Dietary Reference Intakes (DRIs) in the United States and Canada and Dietary Reference Values (DRVs) in the United Kingdom and the European Union.

Table 8a.1: Comparison of the suggested “recommended” terminology with terms in use at present by USA/Canada, UK, European Union/EFSA and WHO/FAO.
AI, adequate intake; AMDR, adequate macro­nutrient distribution range; AR, average require­ment; DRI, dietary reference intake; DRV, dietary reference value; EAR, estimated average require­ment; LRNI, lower reference nutrient intake; LTI, lower threshold intake; NIV, nutrient intake value; PRI, population reference intake; RDA, recommended dietary allowance; RI, reference intake range for macronutrients; RNI, reference nutrient intake (UK), recommended nutrient intake (WHO/FAO); SIV, Safe intake value; SUL, Safe upper level; UL, tolerable upper intake level (USA/Canada & EFSA), upper tolerable nutrient intake level (WHO/FAO).
Adapted from King and Garza (2007).

Recommendation	Recommended terms	USA/Canada	UK	European Union/EFSA	WHO/FAO
Umbrella term for the set of recommendations	NRV	DRI	DRV	DRV
Average requirement	AR	EAR	EAR	AR
Recommended intake level	RI	RDA	RNI	PRI	RNI
Lower reference intake			LRNI	LTI
Adequate intake	AI	AI	SIV	AI
Safe upper level of intake	UL	UL	SUL	UL	UL
Appropriate macronutrient distribution range		AMDR	AMDR	RI	Population mean intake goals

Recom­mendations from the workshop for the terms for three reference values and the relationship between them is shown in Figure 8a.1. The three reference values are: the Average Requirement (AR), Recom­mended Intake (RI), and Safe Upper intake level (UL). Of these, both the AR and UL are used to plan, assess, and evaluate nutrient intakes at the pop­ula­tion level, whereas the RI is the appropriate reference to use for the assessment and planning of intakes for an indi­vidual. However, when there is insufficient evidence to set an AR, then an Adequate Intake (AI) is derived based on observed or experimentally deter­mined estimates for an appar­ently healthy pop­ula­tion. For more details of the derivation of these core reference values, see Sections 8a.2.4 for AR and Section 8a.3 for RI and the AI. This initial organizing framework empha­sizes on the left the concepts that serve as the basis for setting the two recom­mended NRVs. Their uses at both the indi­vidual and pop­ula­tion level are shown on the right, along with other critical health applications of the NRVs. The two core reference values — the AR and the UL — are prioritized, from which other reference values are derived. The indi­vidual recom­mended intake level (RI) is used to guide intakes at the indi­vidual level, and is conven­tionally set to cover the needs of 98% of indi­viduals.

Figure 8a.1: Risk of inadequacy (left y-axis) and risk of excess (right y-axis) as a function of observed level of intake (x-axis). Modified from NASEM (2018).