Evidence that palmitic acid is absorbed assn-2 monoacylglycerol from human milk by breast-fed infants
- 272 Downloads
Milk fatty acids consist of about 20–25% palmitic acid (16∶0), with about 70% of 16∶0 esterified to thesn-2 position of the milk triacylglycerols. Hydrolysis of dietary triacylglycerols by endogenous lipases producessn-2 monoacylglycerols and free fatty acids, which are absorbed, reesterified, and then secreted into plasma. Unesterified 16∶0 is not well absorbed and readily forms soaps with calcium in the intestine. The positioning of 16∶0 at thesn-2 position of milk triacylglycerols could explain the high coefficient of absorption of milk fat. However, the milk lipase, bile salt-stimulated lipase, has been suggested to complete the hydrolysis of milk fat to free fatty acids and glycerol. These studies determined whether 16∶0 is absorbed from human milk assn-2 monopalmitin by comparison of the plasma triacylglycerol total andsn-2 position fatty acid composition between breast-fed and formula-fed term gestation infants. The human milk and formula had 21.0 and 22.3% of 16∶0, respectively, with 54.2 and 4.8% 16∶0 in the fatty acids esterified to the 2 position. The plasma triacylglycerol total fatty acids had 26.0±0.6 and 26.2±0.6% of 16∶0, and thesn-2 position fatty acids had 23.3±3.3 and 7.4±0.7% of 16∶0 in the three-month-old exclusively breast-fed (n=17) and formula-fed (n=18) infants, respectively. Marked differences were found in the plasma total and the 2 position phospholipid percentage of 20∶4ω6, i.e., 11.6±0.3 and 6.9±0.6 (total), 17.7±1.4 and 9.7±0.6 (sn-2 position) and percentage of 22∶6ω3, 4.6±0.3 and 2.1±0.3 (total), 5.6±0.6 and 2.0±0.2 (sn-2 position) for the breast-fed and formula-fed infants, respectively. These studies provide convincing evidence that 16∶0 is absorbed from human milk assn-2 monoacyl-glycerol. The metabolic significance of the differences in positional distribution of fatty acids in the plasma lipids of breast-fed and formula-fed infants is not known.
KeywordsHuman Milk Cholesteryl Ester Milk Fatty Acid Position Fatty Acid Milk Triacylglycerols
Unable to display preview. Download preview PDF.
- 5.Jensen, C., Buist, N.R.M., and Wilson, T. (1988)Am. J. Clin. Nutr. 43, 745–751.Google Scholar
- 17.Innis, S.M., Quinlan, P., and Diersen-Schade, D. (1993)Am. J. Clin. Nutr. 51, 173–182.Google Scholar
- 18.Kuksis, A. (1984)Lipid Res. Methodology 10, 77–131.Google Scholar
- 19.Christie, W.W. (1986) inAnalysis of Oils and Fats (Hamilton, R.J., and Rossell, J.B., eds.) pp. 313–339, Elsevier Applied Science, London and New York.Google Scholar
- 23.Ponder, D.L., Innis, S.M., Benson, J.D., and Siegman, J.S. (1992)Ped. Res. 32, 638–688.Google Scholar