tation of the adequacy of human milk because of a lack of understanding about their derivation for young infants. Although they were based on human-milk composition and volume of intake, the previous RDA and RNI values allowed for the lower bioavailability of nutrients from nonhuman milk. However, where warranted, information on specific changes in the bioavailability or the source of nutrients for use in developing formulations is included in the DRI reports.
Ages 0 through 6 Months. To determine the AI value for infants ages 0 through 6 months, the mean intake of a nutrient was calculated by multiplying the average concentration of the nutrient in human milk produced during the second through sixth month of lactation (derived from consensus values from several reported studies [Atkinson et al., 1995]) by the average volume of milk intake of 0.78 L/day (as reported from studies of full-term infants by test weighing [Butte et al., 1984; Chandra, 1984; Hofvander et al., 1982; Neville et al., 1988]). Because there is variation in both of these measures, the computed value represents the mean. It was assumed that infants have adequate access to human milk and that they consume increased volumes as needed to meet their requirements for maintenance and growth.
Ages 7 through 12 Months. EARs were developed for these older infants for iron, zinc, and protein (IOM, 2001, 2002a). The reference body-weight method was used in the DRI reports to extrapolate the AI for infants 0 through 6 months of age to an AI for older infants in the absence of direct data on older infants (IOM, 1997). The extrapolation method was not deemed appropriate for dietary fats or carbohydrate in the macronutrient report (IOM, 2002a). This is because the amount of energy required on a body-weight basis is significantly lower during the second 6 months of life, due largely to the slower rate of weight gain per kilogram of body weight. Therefore the basis of the AI values derived for this age category for dietary fats and carbohydrate was the sum of the specific nutrients provided by 0.6 L/day of human milk (the average intake of infants in this age group [Heinig et al., 1993]) and that which was provided by their usual intake of complementary weaning foods (Specker et al., 1997). This approach is in keeping with the recommendations of the Canadian Paediatric Society (Canada, 1990), the American Academy of Pediatrics (AAP, 1997), and Nutrition During Lactation (IOM, 1991) for continued feeding of human milk to infants through 9 to 12 months of age with the appropriate introduction of solid foods.