Structural Position and Amount of Palmitic Acid in Infant Formulas: Effects on Fat, Fatty Acid, and Mineral Balance

The structure of the triglycerides (TG) in human milk (HM) differs from those of vegetable oils used in infant formulas. In HM, palmitic acid is predominantly esterified to the center or beta-position of the TG, in vegetable oil, it is mainly at the external or alpha-positions. These differences in configuration affect intestinal fat absorption. Fat and mineral balances were investigated in three groups of 9 healthy term infants aged 5 weeks. Infants were randomly assigned to receive one of the three study formulas from birth: (a) formula beta, resembling the structure of HM fat most closely (24% palmitic acid, 66% esterified to beta-position), (b) formula intermediate (24% palmitic acid, 39% esterified to the beta-position), and (c) regular formula (20% palmitic acid; 13% esterified to the beta-position). Fat absorption was highest in infants fed the beta formula (97.6 +/- 0.9%), intermediate in those fed with the intermediate formula (93.0 +/- 1.8%), and lowest in infants receiving the regular formula (90.4 +/- 4.6%). Fecal calcium excretion was significantly lower in the beta group than in the other two groups (43.3 +/- 18.1 vs. 59.9 +/- 15.1 vs. 68.4 +/- 22.3 mg.kg-1.day-1 for beta, intermediate, and regular respectively). Dietary TG containing palmitic acid predominantly at the beta-position, as in HM, have significant beneficial effects on the intestinal absorption of fat and calcium in healthy term infants.