Many published studies of breast milk FA composition are limited to populations from one or two countries. We aimed to examine the degree to which FA compositions vary across a number of diverse populations. Because diet and maternal adipose stores influence breast milk FA composition, differences in FA composition between groups most likely reflect habitual dietary differences. Approximately 50 breast milk samples (full breast expression) were collected from women in Australia, Canada, Chile, China, Japan, Mexico, Philippines, the United Kingdom, and the United States. The proportion of saturated FA was relatively constant among countries, with the exception of the Philippines, where levels of lauric and myristic acids were elevated (means greater than two times the mean of most other countries). Monounsaturated FA also varied little, with the exception of low levels of oleic acid in the Philippines and high levels of erucic acid in China. Although arachidonic acid (C20:4n-6) levels were similar among all countries (means ranging from 0.36 wt % to 0.49 wt %), mean DHA (C22:6n-3) levels ranged from 0.17 to 0.99 wt %, with the highest levels in Japanese milk and the lowest levels in Canadian and U.S. samples. The results of this study demonstrate that the proportion of saturated and monounsaturated FA are relatively constant across a large number of countries, whereas the level of some of the PUFA, especially DHA, are highly variable.

Objectives:Levels of stool fatty acid soaps and beneficial bacteria differ between formula-fed and breast-fed infants; addition of specific formula ingredients may reduce these differences. This study evaluated the effects of a term infant formula containing high sn-2 palmitate term infant formula (sn-2) or an identical formula supplemented with oligofructose (OF) at 2 concentrations (sn-2+3 g/L OF, sn-2+5 g/L OF) on stool composition, stool characteristics, and fecal bifidobacteria.Methods:Healthy, term formula-fed infants 7 to 14 days old (n = 300) were randomized in a double-blind manner to receive standard formula (control), sn-2, sn-2+3 g/L OF, or sn-2+5 g/L OF for 8 weeks. Human milk (HM)–fed infants (n = 75) were studied in parallel. Stool samples were collected from all subjects at week 8 for fatty acid soaps and mineral content, and from a subset at baseline and week 8 for bifidobacteria. Stool characteristics were assessed via 3-day diary.Results:The sn-2 group had 46% less stool soap palmitate (P < 0.001) and softer stools than control (20% more mushy soft stools, P = 0.026; 50% fewer formed stools, P = 0.003). Addition of OF resulted in even fewer formed stools versus control (65% fewer for sn-2+3 g/L OF, 79% fewer for sn-2+5 g/L OF), with 5 g/L OF more closely resembling that of HM-fed infants. Both sn-2 (P < 0.05) and sn-2 with OF groups (P < 0.01) had significantly higher fecal bifidobacteria concentrations than control at week 8, not differing from HM-fed infants.Conclusions:High sn-2-palmitate formulas led to reduced stool soaps, softer stools, and increased bifidobacteria, whereas addition of OF further improved stool consistency. Those modifications brought outcomes in formula-fed infants closer to that in HM-fed infants.

These studies provide evidence that palmitic acid can be efficiently absorbed, avoiding fatty soap formation of it is present in the sn-2 position.

Human milk fat is well absorbed despite its large concentration of long-chain saturated fatty acids (LCSFA), particularly palmitic acid. The superior absorption has been ascribed in part to the uncommonly high proportion of the palmitic acid in the sn-2 position of the triglycerides, 70% in human milk triglycerides compared with 10-15% in the fats and oils commonly used in infant formula blends. Colipase-dependent pancreatic lipase selectively hydrolyzes the fatty acids at the sn-1 and 3 positions, yielding free fatty acids and the 2-monoglyceride, which are absorbable. Free palmitic acid, but not monopalmitin, can be lost as calcium soaps in the feces. The present study demonstrated that mixtures of coconut oil and palm olein are better absorbed by rats if the proportion of LCSFA in the sn-2 position is increased by the process of chemical randomization, in which the fatty acids of the native oils are redistributed equally to all three positions in the rearranged triglycerides. The fecal excretion of total fatty acids, essentially LCSFA, from the mixtures in which the oils were randomized together (corandomized) was 30 to 60% less than from the mixtures of native oils.