Since the publication of the tenth edition of Recommended Dietary Allowances (NRC, 1989a) in the United States and Canadian Recommended Nutrient Intakes (Health Canada, 1990), there has been a significant expansion and evolution of the research base in relation to a move toward defining functional endpoints that are relevant to the understanding of nutrient requirements and food constituents and their relationship to a number of aspects of human health.
These advances allow the refinement of the conceptual framework for defining nutrient requirements quantitatively and a clearer determination of the legitimate uses of nutrient requirement estimates and their derivatives in the interpretation and use of dietary intake data. Such uses might broadly be categorized according to whether they are (a) prescriptive or planning applications, where suitable levels of nutrient intake by individuals and/or population groups are established, and (b) diagnostic or assessment applications, where determinations are made about the likely nutritional adequacy of the observed intake when considered in relation to appropriate nutrient requirement data. Major differences in the types of information required about nutrient needs and relevant nutrient intake data are fundamental to appropriately focusing on the individual or on a defined population group (Beaton, 1994).
Neither the RDAs nor the Canadian RNIs have been applied appropriately in many settings. The availability of only a single type of reference value in the face of various needs has led to inappropriate applications. Moreover, inconsistent methods and criteria for deriving certain RDAs and RNIs and insufficient documentation of approaches and criteria have also contributed to inappropriate applications.
In these times of extensive international collaboration, agricultural and food exchange, and global nutrition-related health problems, harmonization of nutrient-based dietary standards between Canada and the United States is viewed as a first step, with the expectation that Mexico will be able to join in the near future. Such harmonization within the North American continent would further global development of similar efforts. Although the same general approaches have been used by most countries in developing recommended nutrient intakes (e.g., RDAs in the United States, RNIs in Canada, and Dietary Reference Values [DRVs] in Great Britain), and physiological requirements for nutrients are expected to be similar across healthy population groups, many of the quantitative values that have emerged from the different national expert groups are quite divergent, largely reflecting differences in the interpretation and use of scientific data and often based on different food