Characterization of Newborn Fecal Lipid

Abstract

Fecal lipid excretion was quantitated and analyzed in two groups of normal infants 3 to 11 days and 23 to 72 days of age. Total lipid excretion was similar in both groups averaging 10.8% of dietary intake. Fecal lipid was partitioned into four fractions: neutral lipids, insoluble divalent calcium soaps, ionized fatty acids and bound lipids. The neutral lipid fraction predominated in both groups, equalling 56 ± 5.3% (mean ± S.E.M.) of fecal lipid. It contained significant quantities of glycerides (13.6 ± 6.0% of the total lipid excreted). Calcium soaps comprised the other major fraction (25 ± 5.3%); analysis of this fraction by gas liquid chromatography showed that it contained primarily long-chain saturated fatty acids. The demonstration of glycerides in fecal lipid establishes that lipolysis is defective in newborn infants. Identification of long-chain saturated fatty acids in the calcium soap fraction documents the association between calcium and saturated fatty acid excretion. The presence of fecal monoglyceride, while conceivably the result of colonic bacterial hydrolysis of triglyceride, raises the possibility that lipid micellization and/or mucosal transport is insufficient for optimal lipid absorption. Thus, the intraluminal phase and possibly the mucosal phase of lipid absorption are not fully developed in the full-term newborn infant.