Factors Determining Optimal Fatty Acid Absorption in Preterm Infants.

Objectives: The aim of the present study was to quantify absorption coefficients of specific fatty acids in preterm infants as a function of diet, formula or breast milk (BM), and postnatal age; to identify the fatty acid structural characteristics that determine optimal fatty acid absorption.

Methods: Fatty acids from dietary and fecal samples were extracted and quantified by gas chromatography-mass spectroscopy. Fatty acid absorption coefficients (FA-CFAs) were calculated by comparing the total amount of fatty acids supplied by the diet to the amount quantified in the total fecal output during a 3-day period.

Results: A total of 18 infants (BM 8, formula 10) were studied at 2 weeks of age, and 20 infants (BM 10, formula 10) were studied at 6 weeks of age. FA-CFAs decreased with increasing carbon length in formula-fed infants at 2 and 6 weeks. Results were similar but less in magnitude in BM-fed infants at 2 weeks with no difference at 6 weeks.

Conclusions: Preterm infants fed formula demonstrated lower FA-CFAs as a function of increasing carbon length. This is consistent with limited pancreatic lipase production and with lipase being present in BM but not in formula. The fact that this pattern was seen in BM-fed infants at 2 weeks but not 6 weeks of age suggests that intestinal immaturity may also play a role in impaired fatty acid absorption. These data highlight principles that need to be considered to optimize delivery and absorption of dietary long-chain polyunsaturated fatty acids in preterm infants.