Fats play a vital role infant growth, development and health not only as a source of energy, but as a source of essential fatty acids, complex lipids and bioactive components. In a recently held webinar, Associate Professor Jose M Saavedra discussed the role of sn-2 palmitic acids in enhancing fat and calcium absorption from milk.
Associate Professor Jose M Saavedra
Johns Hopkins University School of Medicine
Baltimore, Maryland, USA
Lipids comprise the second largest component of human milk and provides about 50% of an infant’s energy intake.1 Most fat in human milk occurs in the form of triacylglycerols (TGs), i.e. three fatty acids are esterified to a glycerol backbone at the sn-1, sn-2 and sn-3 positions. Palmitic acid and oleic acid comprise the majority of fatty acids in TGs of human milk.
Using the right vegetable fat combination, the fatty acid composition and total palmitic acid concentration in infant formula can be made comparable to human milk. However, the stereotypic distribution of fatty acids on TGs of human vs. vegetable fat is vastly different. In human milk, 70% of the palmitic acid is in the sn-2 position; 2,3 in contrast, in most vegetable oil blends used in infant formula, less than 10% of the palmitic acids is in the sn-2 position.
These differences in stereospecificity of palmitic acid within the triglyceride molecule impact nutrient absorption. Pancreatic lipase digestion of triglycerides with palmitic acid in the sn-2 position maximizes absorption of fat (overall), palmitic acid and calcium [Figure 1]. In contrast, cleavage of palmitic acid in the sn-1 and sn-3 positions yields free palmitic acids that bind with calcium in the intestinal lumen to form insoluble calcium soaps that are then excreted.
Figure 1. The stereospecificity of palmitic acid in triglycerides impact the absorption of fat and calcium.
Most infant formulas have adequate amounts of total palmitic acid from palm olein, but most of these are in the sn-1 and sn-3 position. Reducing the total amount of palmitic acids in infant formula can potentially reduce the amount of sn-1 and sn-3 palmitic acids, and consequently reduce soap formation and thereby improve fat and calcium absorption.4 However, this will also lead to a reduction in absorbable palmitic acid, a major fatty acid in early adipose tissue in early infancy. Another approach to improving triglyceride and fatty acid profile of infant formula is to add structured triglycerides with palmitic acid in the sn-2 position.5 This approach makes it possible to provide palmitic acid in levels similar to human milk, while minimizing any impact on nutrient absorption.
Studies have shown that the use of formula with high sn-2 palmitate content improves fatty acid absorption and calcium absorption, the latter resulting from reduced stool soap formation.6,7,8 Furthermore, studies have shown that infants the use of infant formula with high sn-2 palmitic acid conferred beneficial effects on markers of bone health, i.e. improved bone mineral content and bone density.6,9,10
Apart from reducing calcium and fatty acid absorption, the formation of calcium soaps is also known to contribute to stool hardening and intestinal discomfort. The use of infant formula with high sn-2 palmitic acid has been shown to decrease hard stools and crying time.6,10,11
The composition of fatty acids in human milk is unique and critical for delivering energy as well as structural components for infant growth and development. The human milk delivers palmitic acid in a very specific form – as sn-2 fatty acid – that maximizes its absorption as well as that of calcium. In formula-fed infants, the substitution of palmitic acid from vegetable fats with lipids that are high in sn-2 palmitic acid enhances palmitic acid absorption, decreases soap formation and hard stools, and improves calcium absorption and bone mineral content in the infant.
- Ballard O, Morrow AL. Human milk composition: nutrients and bioactive factors. Pediatr Clin North Am. 2013 Feb;60(1):49-74.
- Giuffrida F, et al. Quantification of 1,3-olein-2-palmitin (OPO) and palmitic acid in sn-2 position of triacylglycerols in human milk by liquid chromatography coupled with mass spectrometry. Molecules. 2018 Dec 21;24(1):22.
- Prosser CG, et al. Composition and distribution of fatty acids in triglycerides from goat infant formulas with milk fat. J Dairy Sci. 2010 Jul;93(7):2857-62.
- Nelson SE, Frantz JA, Ziegler EE. Absorption of fat and calcium by infants fed a milk-based formula containing palm olein. J Am Coll Nutr. 1998 Aug;17(4):327-32.
- Miles EA, Calder PC. The influence of the position of palmitate in infant formula triacylglycerols on health outcomes. Nutr Res. 2017 Aug;44:1-8.
- Kennedy K, et al. Double-blind, randomized trial of a synthetic triacylglycerol in formula-fed term infants: effects on stool biochemistry, stool characteristics, and bone mineralization. Am J Clin Nutr. 1999;70(5):920–927.
- Bar-Yoseph F, et al. sn2-palmitate reduces fatty acid excretion in chinese formula-fed infants. J Pediatr Gastroenterol Nutr. 2016;62(2):341–347.
- Yao M, et al. Effects of term infant formulas containing high sn-2 palmitate with and without oligofructose on stool composition, stool characteristics, and bifidogenicity. J Pediatr Gastroenterol Nutr. 2014 Oct;59(4):440-8.
- Béghin L, Marchandise X, Lien E, Bricout M, Bernet JP, Lienhardt JF, Jeannerot F, Menet V, Requillart JC, Marx J, De Groot N, et al. Growth, stool consistency and bone mineral content in healthy term infants fed sn-2-palmitate-enriched starter infant formula: A randomized, double-blind, multicentre clinical trial. Clin Nutr. 2019 Jun;38(3):1023-1030.
- Litmanovitz I, et al. High beta-palmitate formula and bone strength in term infants: a randomized, double-blind, controlled trial. Calcif Tissue Int. 2013 Jan;92(1):35-41.
- Litmanovitz I, et al. Reduced crying in term infants fed high beta-palmitate formula: a double-blind randomized clinical trial. BMC Pediatr. 2014 Jun 19;14:152.