Feeding the low-birth-weight infant. IV. Fat absorption as a function of diet and duodenal bile acids.

Fat absorption and fasting duodenal bile acids were studied at 11 to 68 days of age in 66 healthy preterm infants, gestational age of 31 to 36 weeks and birth weight of 1,230 to 2,160 g. The infants fed human milk received pooled, expressed milk (55%), partly supplemented (35%) with their own mother's expressed milk. Approximately 10% of the milk was given by breastfeeding once per day. All expressed human milk not fed immediately was pasteurized at 62 degrees C for 30 minutes. The other three groups of infants received an adapted formula (F1), F1 supplemented with taurine (F2), or F1 supplemented with taurine and cholesterol (F3). In each group, fat was provided at 6.75 g/kg/d. The formulas had a fat concentration of 4.5 g/100 mL, containing 57.6% of unsaturated fatty acids from vegetable oils. In the infants fed human milk, fat absorption was consistently high, and no correlation was found between fat absorption and postnatal age. In the formula-fed infants, fat absorption increased with postnatal age (r = .310 P less than .05). When the duodenal concentration of total bile acids was above the median (3.6 mmol/L), fat absorption in the formula-fed infants exceeded 80%. There was a linear correlation between fat absorption and duodenal bile acids (r = .630, P less than .001) in the formula-fed infants. In the infants fed human milk, such correlation was not observed, and their intraluminal concentration of bile acids always exceeded 3.6 mmol/L.