Ages 0 through 6 Months. On the basis of the method described in Chapter 2 and the manganese concentration of milk produced by well-nourished mothers, the AI reflects the observed mean manganese intake of infants exclusively fed human milk during their first 6 months. There are no reports of full-term infants exclusively and freely fed human milk by U.S. or Canadian mothers who manifested any signs of manganese deficiency (Davidsson et al., 1989a). Mean manganese concentrations of human milk at 1 month were approximately 4.0 μg/L (Aquilio et al., 1996; Casey et al., 1985, 1989) and declined to 1.87 μg/L by 3 months postpartum (Casey et al., 1989) (Table 10-2). Total manganese secretion in human milk averaged 1.9 μg/day over the first 3 months and 1.6 μg/day over the second 3 months (Casey et al., 1989). Based on the above data, the AI is set according to average milk volume consumption (0.78 L/day) × the average manganese concentration in human milk (3.5 μg/L), or 3 μg/day, after rounding (see Chapter 2).