Very little information is available on metabolic water production in infants. In one study, the metabolic water production in 10- to 15-month-old infants was 13 percent of water turnover (Fusch et al., 1993), a value similar to that found in adults.
Milk Consumption. Infants exclusively fed human milk do not require supplemental water. This is true not only during temperate climatic conditions, but also in hot and humid climates (Almroth and Bidinger, 1990; Cohen et al., 2000). It is also true for term infants with low birth weight (Cohen et al., 2000).
Average total daily intake of water of all sources in the first year of life was 130 mL/kg/day based on data from 296 infants in the 1994–1996 Continuing Survey of Food Intake by Individuals (CSFII) conducted by the U.S. Department of Agriculture (Heller et al., 2000). This total intake of water decreased significantly to 108 mL/kg/day in year two. Non-Hispanic blacks had the highest total water consumption (129 mL/kg/day), while non-Hispanic whites had the lowest consumption (113 mL/kg/day) (Heller et al., 2000).
As discussed in Chapter 2, the average volume of human milk consumed during the first 6 months of life is estimated to be 0.78 L/day. Because approximately 87 percent of the volume of human milk exists as water, approximately 0.68 L/day (0.78 × 0.87) of water is consumed. Therefore the AI for total water for infants 0 through 6 months of age is set at 0.7 L/day after rounding to the nearest 0.1 L.
Milk volume for infants 7 to 12 months of age has been estimated to be 0.6 L/day (see Chapter 2). Water intake for older infants can be determined by estimating the water intake from human milk (concentration × 0.6 L/day) and from complementary foods and other beverages (see Chapter 2). Water intake data from complementary foods and beverages other than human milk was estimated to be 0.32 L/day based on data from the CSFII (Appendix E).4 The average water intake from human milk is approximately 0.52 L/day (0.87 × 0.6 L/day). Thus the total water intake is estimated to be 0.84
The sample population includes breastfeeding infants with two 24-hour diet recalls; infants consuming more than 62 g (approximately 1/4 cup) fluid milk and/ or infant formula on either of the survey days were not included in the analyses. Means and standard errors were calculated with WesVar Complex Samples 3.0. Total water intake reflects the sum of plain drinking water and the water content of all foods and beverages consumed. Data on plain drinking water intake were provided by a proxy in response to the question, “How many fluid ounces of plain drinking water, that is, tap water or any bottled water that is not carbonated, with nothing added to it, did you drink yesterday?”