Effects of Nutrition Supplementation on Osmolality of Expressed Human Milk

Abstract

Background Provision of human milk to premature infants optimizes outcomes, but it must be supplemented to meet their nutrient and caloric requirements for growth. Our objective was to quantify the osmolality of human milk mixed with commercially available human milk fortifiers (HMF) and powdered infant formula, as currently fed to premature infants, simulating standard neonatal intensive care unit feeding practices for mixing and refrigerator storage. Methods Expressed human milk (EHM) samples obtained from mothers of premature infants (≤32 weeks gestation) were mixed with standard commercial products, and osmolalities were quantified. Results HMF significantly increased the micronutrient content and osmolality of EHM. Osmolalities were 291 ± 6 mOsm/kg (mean ± SD) for unsupplemented milk, and 505 ± 5 and 315 ± 19 mOsm/kg after supplementation to 24 kcal/oz using 2 current U.S. Liquid EHM fortifiers. When using powdered infant formulas to further increase the caloric content of fortified EHM >24 kcal/oz, osmolalities increased by 10.5–23.0 mOsm/kg for each additional kcal/oz. The use of powdered formulas alone (without HMF) increased osmolality without comparable increases in nutrient content. Refrigeration for 24 hours did not affect osmolalites. Conclusion Our finding that several common feeding formulations exceed 450 mOsm/kg, and the lack of evidence of adverse effect, raise the question of whether current maximum osmolality guidelines should be reevaluated to enable optimal nutrition for infants in neonatal intensive care.

Fortifier selection and dosage enables control of breast milk osmolarity

“…Subsequently, we studied the effect of HMFs on osmotic concentration. In agreement with previous publications, we observed that osmolality of BM increases significantly upon fortification and that osmolality of fortified BM increases with time unlike that of plain BM, which remains constant [22,23,25,27,29]. Lamport et al studied two liquid HMFs and four powder infant formulas to achieve different caloric targets and they obtained osmolalities higher than 450 mOsm/kg as we have observed.…”

“…Moreover, Aceti et al showed that values below 450 mOsm/kg do not result into an increase in reflux in premature newborns [38]. Nevertheless, in the last years, Miyake et al and Lamport et al had raised the need to reevaluate the maximum osmolality recommended by the APP [24,25]. In our hands, BM fortified with HMF Almirón Fortifier1 or NANFM851 induced osmolalites clearly over the limit recommended by AAP.…”

“…The AAP advises not to exceed 450 mOsm/kg in enteral nutrition [20] based on studies showing an association between high osmolality food and necrotizing enterocolitis [33,34]. Although the threshold remains controversial [24,25,35,36], many studies indicate a correlation between osmolality and gastrointestinal complications [35,[37][38][39]. For instance, Salvia et al quantified reflux episodes in children from 12 months to 12 years by pH metric comparing quantity and osmolality of the food (500 mOsm/kg) concluding that osmolality delayed gastric emptying and increased the gastroesophageal reflux [37].…”

“…Hence, the American Academy of Pediatrics (AAP) advises that osmolality for enteral nutrition should not exceed 450 mOsm/kg (400 mOsm/L) [20]. Breast milk osmolality alone is already 300±6 mOsm/kg [15,[21][22][23] and recent reports describe that many HMFs increase osmolality above the recommended maximum levels [22,24,25]. Moreover, these studies do not include NSs, which are indicated for delicate and sick neonates in addition to HMFs [26] and may further increase osmotic concentration.…”

Effect of Target Fortification on Osmolality and Microbiological Safety of Human Milk Over Time

“…In our study, we investigated how target fortification can modify the osmolality of pasteurised donor human milk and raw mature milk over time. The osmolality of human milk before fortification was on average of 289 mOsm/L, which is comparable to the other results in the literature (26–30). After target fortification (based on the analysis of breast milk composition and addition of adequate individual targeted macronutrients), we found that the osmolality increased up to the 30% immediately after fortification.…”