Nutrient Requirements International Perspectives

A A Yates, ENVIRON Health Sciences, Arlington, VA, USA

© 2005 Elsevier Ltd. All rights reserved.

Determining human requirements for nutrients has been a major activity for nutritionists, biochemists, and physiologists for the past 100 years since the advent of methods that have allowed for their isolation, quantification in food, and determination of their function in cell and whole body metabolism. Whereas initial efforts focused on identifying constituents in food required to maintain life and promote growth and thus were considered essential or indispensable, research during the past 60 years has become increasingly focused on elucidating the specific roles each nutrient plays in health and quantifying, through experimentation and study of healthy populations, the amounts needed on a daily basis to provide for optimal health and prevent disease. This process of estimating requirements for an individual with any level of precision is still in the early stages of development. Nevertheless, many facets of maintaining and improving the health of the public hinge on knowing how much is needed of which nutrients or chemical components of food, and how this differs at different stages of growth and development.

Multiple terms have been adopted to define nutrient requirements, allowances, or standards (Table 1). They have been established or adopted by various countries and then used for the major functions of planning food programs or assessing diets for adequacy or excess (Figure 1). Major efforts during the past two decades by nutrition scientists throughout the world have resulted in a shift from establishing and periodically revising nutrient allowances or recommendations based on general consensus of adequate levels (e.g., the Recommended Dietary Allowances (RDAs) of the Food and Nutrition Board in the United States, the Recommended Nutrient Intakes (RNIs) of Canada, or the Safe Levels of Intake derived by the expert groups convened by the World Health Organization and Food and Agriculture Organization of the United Nations) to more definitively anchoring the reference values to specific, well-described scientific studies so that when new information becomes available from research, it is clear that new evaluations need to be undertaken. For example, in the past, the RDAs in the United States have been used as the reference values in many situations, from setting the standards for nutrient content in programs that provide single meals, such as in school lunch programs, to the basis for government reimbursement for costs of care in skilled nursing homes (Table 2). It is not surprising that one reference value or number, even when adjusted for age or body size and based on scientific studies, is at times not appropriate for the situation in which it is used.

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