range weighing 50 kg (110 lb), 55 kg (121 lb), or 70 kg (154 lb) despite the differences in size and energy expenditure.
Reference weights are provided (Chapter 1, Table 1-2) to allow a calculation, when necessary, of the amount of nutrient per unit of body weight for individuals who are greatly outside the typical range of body size. These weights may also be useful for infants and children, whose average weights change substantially with age. Ordinarily, adjusting values for the nutrients included in this report based on reported energy intake has not been recommended; little justification for this practice could be found in the literature for individuals eating typical diets.
Although RDAs have been used to assess the adequacy of an individual’s nutrient intake in the past, this practice has serious limitations if a person’s intake is less than the RDA. An individual’s nutrient requirement is never known with certainty; only the approximate distribution of requirements for the life stage group may be known. If the individual’s intake on average meets or exceeds the RDA, there is good assurance that the intake is adequate for the specified criterion. If an individual’s average intake over time is less than the RDA, it can be inferred only that there is some increased likelihood that the intake is inadequate. The likelihood increases the further the intake falls below the RDA. For a requirement that is normally distributed, when the usual intake is less than 2 standard deviations below the Estimated Average Requirement (EAR), the likelihood that the individual’s requirement would be met would be small (NRC, 1986). A usual intake that is well below the RDA may indicate the need for further assessment of nutritional status by biochemical tests or clinical examination.
As is true for the Recommended Dietary Allowance (RDA), healthy individuals with an average daily intake at or above the Adequate Intake (AI) are assumed to be at low risk of intake inadequate for a defined state of nutrition. This is its most important use. Similarly, if an individual’s average intake over time is less than the AI, it can be inferred only that there is some likelihood that the intake is inadequate. The likelihood increases the further the intake falls below the AI. Just as with the RDA, a usual intake that is well below