Bile salt-stimulated lipase and digestion of non-breast milk fat.

Abstract

13 Carbon (13C)-lipid breath tests are an effective, noninvasive way of repeatedly measuring fat digestion. The purpose of this study was to assess the contribution of bile salt-stimulated lipase (BSSL) in human milk to the digestion of non-breast-milk fat in Gambian infants. Twelve Gambian infants (aged 3-8 months) were studied on 4 days. 13C-Trioctanoin (7.5 mg/kg, digested by BSSL preduodenal and pancreatic lipases) and 13C-cholesteryl octanoate (25 mg/kg, digested by BSSL and pancreatic lipases) were used as substrates. The percentage dose recovery (PDR) of 13C in breath during 5 hours was compared after ingestion of each substrate with fresh, expressed breast milk (FBM) or heated, expressed breast milk (HBM). Gas isotope ratio-mass spectrometry was used to measure 13C enrichment, and breast milk samples were analysed for esterase activity. Heating breast milk significantly decreased esterase activity (mean +/- SD values: FBM = 12.2 +/- 2.9 IU/ml; HBM = 0.5 +/- 0.3 IU/ml), and there was no difference in the volumes of milk ingested on each test day (approximately 50 ml). The PDR of 13C was comparable to that previously described in healthy English infants and was not increased by BSSL. The mean +/- SD PDR of 13C from trioctanoin was 36.3 +/- 8.4% for FBM and 34.6 +/- 6.3% for HBM (NS). From cholesteryl octanoate, the mean +/- SD PDR of 13C was 24.3 +/- 8.7% for FBM and 27.1 +/- 7.5% for HBM (NS). Bile salt-stimulated lipase may enhance fat digestion in younger or malnourished infants who have a greater degree of pancreatic enzyme deficiency. However, this study suggests that it does not increase the digestion of non-breast-milk fat in healthy, well-nourished infants aged 3 to 8 months from an underprivileged background, who typically ingest frequent small quantities of breast milk.