See “Effect of Fortifiers and Additional Protein on the Osmolarity of Human Milk: Is It Still Safe for the Premature Infant?” by Kreissl et al on page 432.
In 2010, The European Society for Pediatric Gastroenterology, Hepatology, and Nutrition Committee on Nutrition reported new guidelines on the composition of the enteral nutrient supply of preterm infants (1). In particular, a higher protein supply was advised in the fortification of human milk. In this issue of the Journal of Pediatric Gastroenterology and Nutrition, Kreissl et al report on the effects of the addition of fortifiers and protein on the osmolarity of human milk (2). In particular, protein fortification >2 g/dL may lead to a osmolarity >500 mOsmol/L. Are the new guidelines therefore potentially dangerous for the immature gut?
In 1999, De Curtis et al (3) reported on osmolalities of fortified human milk up to 350 mOsmol/kg H2O. The Cochrane meta-analysis of human milk fortification for preterm infants in 2004 (4) and that on fortification after hospital discharge (5) reported no clear adverse effects of fortification. Pearson et al (6) reviewed human milk fortification and tried to answer the question: does milk osmolality matter? After a broad explanation of the difference between osmolality and osmolarity, they reviewed all of the literature on the possible injury of gut mucosa by high osmolality. No evidence was found for a causal relation between the osmolality of nutrients and the development of necrotizing enterocolitis. A delay in gastric emptying could be observed if the osmolality was >450 mOsmol/kg; however, a warning was issued about the practice of feeding oral high osmolar electrolyte supplements and medications.
Although direct evidence of gut injury has not been found, it may be advisable to investigate the possible adverse effects of high-protein fortification in future meta-analytical studies and to be cautious with protein fortification >2 g/dL leading to osmolarities >450 mOsmol/L, as reported by Kreissl et al. Simultaneous addition of multivitamins, electrolyte solutions, or other high osmolar substances should be avoided.
1. Kreissl A, Zwiauer V, Repa A, et al. Effect of fortifiers and additional protein on the osmolarity of human milk: is it still safe for the premature infant? J Pediatr Gastroenterol Nutr
2. Agostoni C, Buonocore G, Carnielli VP, et al. Enteral nutrient supply for preterm infants: commentary from the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition Committee on Nutrition. J Pediatr Gastroenterol Nutr
3. De Curtis M, Candusso M, Pieltain C, et al. Effect of fortification on the osmolality of human milk. Arch Dis Child Fetal Neonatal Ed
4. Kuschel CA, Harding JE. Multicomponent fortified human milk for promoting growth in preterm infants. Cochrane Database Syst Rev
5. Young L, Embleton ND, McCormick FM, et al. Multinutrient fortification of human breast milk for preterm infants following hospital discharge. Cochrane Database Syst Rev
6. Pearson F, Johnson MJ, Leaf AA. Milk osmolality: does it matter? Arch Dis Child Fetal Neonatal Ed