milk or other formula may be lower than from human milk. Studies by Fomon and Nelson (1993) involving 40 human milk-fed, 252 cow milk formula-fed, and 135 soy protein formula-fed infants found absorption fractions of 58, 38, and 34 percent, respectively, for the three feeding types. However, the greater daily intake of calcium by the formula-fed infants (327 mg [8.2 mmol], 464 mg [11.6 mmol], and 652 mg [16.3 mmol] for human milk, cow milk, and soy milk infants, respectively) led to net calcium retention that was very similar among the three feeding types, with slightly higher values for the formula-fed infants. The bioavailability of minerals from protein hydrolysate formulas may be lower than from human milk, as indicated in studies in humans (Rigo et al., 1995) as well as in infant rhesus monkeys (Rudloff and Lonnerdal, 1990). However, since these studies were performed using a greater total intake of calcium from infant formulas compared with human milk, it is difficult to interpret the dietary bioavailability.
Numerous studies have compared whole body or regional bone mineral accretion in infants fed human milk, cow milk formula, or soy formula (Chan et al., 1987; Greer et al., 1982b; Hillman et al., 1988; Mimouni et al., 1993; Pittard et al., 1990; Specker et al., 1997; Steichen and Tsang, 1987). Results have varied, but there appears to be a greater bone mineral accretion in cow milk formula-fed infants compared with those fed human milk or soy formula. In spite of this trend, there is no evidence that this difference is beneficial or clinically significant.
No published studies indicate that increasing bone accretion using high calcium-containing formulas or cow milk during infancy leads to greater bone mineralization in later childhood or adolescence. In contrast, Bishop et al. (1996) suggested that premature infants fed human milk in early neonatal life, as opposed to cow milk formula with greater mineral content, may have greater BMC at 5 years of age. This finding is supported by a study in dogs suggesting that in forming stable bone, low calcium intakes early in life might be preferred to greater intakes (Gershoff et al., 1958). These findings need to be replicated to determine whether this effect is relevant to full-term infants. The possibility that “programming” of infants such that lower intakes and retention of calcium is beneficial to long-term mineralization is therefore possible but unproven. Further research is needed to define the risks and possible benefits of high calcium intakes during infancy.
Assuming an efficiency of calcium absorption of 38 percent from cow milk-based formula (Fomon and Nelson, 1993) with a calcium content approximately 50 percent higher than that from human