Abstract
BackgroundFormula-fed (FF) infants often have harder stools and higher stool concentrations of fatty acid soaps compared to breastfed infants. Feeding high sn-2 palmitate or the prebiotic oligofructose (OF) may soften stools, reduce stool soaps, and decrease fecal calcium loss.MethodsWe investigated the effect of high sn-2 palmitate alone and in combination with OF on stool palmitate soap, total soap and calcium concentrations, stool consistency, gastrointestinal (GI) tolerance, anthropometrics, and hydration in FF infants. This double-blind trial randomized 165 healthy term infants 25–45 days old to receive Control formula (n = 54), formula containing high sn-2 palmitate (sn-2; n = 56), or formula containing high sn-2 palmitate plus 3 g/L OF (sn-2+OF; n = 55). A non-randomized human milk (HM)-fed group was also included (n = 55). The primary endpoint, stool composition, was determined after 28 days of feeding, and was assessed using ANOVA accompanied by pairwise comparisons. Stool consistency, GI tolerance and hydration were assessed at baseline, day 14 (GI tolerance only) and day 28.ResultsInfants fed sn-2 had lower stool palmitate soaps compared to Control (P =0.0028); while those fed sn-2+OF had reduced stool palmitate soaps compared to both Control and sn-2 (both P <0.0001). Stool total soaps and calcium were lower in the sn-2+OF group than either Control (P <0.0001) or sn-2 (P <0.0001). The HM-fed group had lower stool palmitate soaps, total soaps and calcium (P <0.0001 for each comparison) than all FF groups. The stool consistency score of the sn-2+OF group was lower than Control and sn-2 (P <0.0001), but higher than the HM-fed group (P <0.0001). GI tolerance was similar and anthropometric z-scores were <0.2 SD from the WHO growth standards in all groups, while urinary hydration markers were within normal range for all FF infants.ConclusionsIncreasing sn-2 palmitate in infant formula reduces stool palmitate soaps. A combination of high sn-2 palmitate and OF reduces stool palmitate soaps, total soaps and calcium, while promoting softer stools.Trial registrationThis study was registered on http://www.clinicaltrials.gov: number NCT02031003.Electronic supplementary materialThe online version of this article (doi:10.1186/1475-2891-13-105) contains supplementary material, which is available to authorized users.
Highlights
Formula-fed (FF) infants often have harder stools and higher stool concentrations of fatty acid soaps compared to breastfed infants
Of the free fatty acids, saturated fatty acids are less readily absorbed than unsaturated fatty acids and have the potential to form insoluble fatty acid soaps, which can result in the loss of both calcium and energy in the feces
23 infants per group were required for 90% power to detect a mean (SD) between-group difference of 7% (7%) in fatty acid soaps at α = 0.05; and 40 infants per group were required for 90% power to detect a mean (SD) betweengroup difference of 0.3 (0.4) points in the five-point stool consistency scale at α = 0.05 (Details on these calculations are provided in the Additional file 1)
Summary
Formula-fed (FF) infants often have harder stools and higher stool concentrations of fatty acid soaps compared to breastfed infants. IF ingredients may interact with each other, and the evaluation of isolated ingredients is insufficient in assessing these complex relationships One example of such interactions involves the digestion of triglycerides and the subsequent absorption of fatty acids and calcium [1], processes which are dependent on both lipid structure and intestinal environment (such as colonic bacterial populations and pH). The selective activity of pancreatic lipase on the sn-1 and sn-3 positions of the triglyceride generates two free fatty acids and a corresponding sn-2 monoglyceride. This sn-2 monoglyceride is readily absorbed regardless of the structure of its esterified fatty acid [1]. Since any reduction in stool soap formation is likely to result in reduced fecal loss of both energy and calcium, the development of a structured triglyceride (closer to HM with high sn-2 PA) and its addition to IF will be of benefit to FF infants
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