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

Background: (13) Carbon (C-13)-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. Methods: Twelve Gambian infants (aged 3-8 months) were studied on 4 days. C-13-Trioctanoin (7.5 mg/kg, digested by BSSL preduodenal and pancreatic lipases) and C-13-cholesteryl octanoate (25 mg/kg, digested by BSSL and pancreatic lipases) were used as substrates. The percentage dose recovery (PDR) of C-13 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 C-13 enrichment, and breast milk samples were analysed for esterase activity. Results: Heating breast milk significantly decreased esterase activity (mean +/- SD values: FBM = 12.2 +/- 2.9 IU/ml; HEM = 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 C-13 was comparable to that previously described in healthy English infants and was not increased by BSSL. The mean +/- SD PDR of C-13 from trioctanoin was 36.3 +/- 8.4% for FBM and 34.6 +/- 6.3% for HEM (NS). From cholesteryl octanoate, the mean +/- SD PDR of C-13 was 24.3 +/- 8.7% for FBM and 27.1 +/- 7.5% for HBM (NS). Conclusions: 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-breastmilk fat in healthy, well-nourished infants aged 3 to 8 months from an underprivileged background, who typically ingest frequent small quantities of breast milk.