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Milk feed osmolality and adverse events in neonates: a systematic review

Osmolality in the range of 300-500 mOsm/kg does not negatively impact gastrointestinal symptoms in neonates, a recent review states.

Osmolality of feeds is an often-misunderstood topic in preterm nutrition. Nutricia’s scientists in close collaboration with independent experts in the field systematically reviewed the literature on milk feed osmolality and adverse gastrointestinal events in preterm infants.

This newly published systematic review demonstrates there is no consistent evidence that feeds in the range of 300-500 mOsm/kg are associated with adverse gastrointestinal symptoms, including necrotising enterocolitis (NEC), in neonates.

Better neonatal care has improved short-term clinical outcomes in preterm infants

However, long-term health, in particular cognitive development, remains a concern in preterm infants. Poor postnatal growth is associated with adverse short- and long-term clinical outcomes. Nutritional management is key for growth; however, the rate of enteral feed advancement can be impacted by feeding (in)tolerance. Due to the high nutritional and caloric needs of preterm infants both fortified human milk and preterm formula has a higher osmolality than human milk alone.

 Unsubstantiated recommendation since 1976

Recent feeding guidelines for preterm infants do not include an upper recommended level of feed osmolality/osmolarity. However, in 1976 the American Academy of Pediatrics recommended that formulae for all infants should have an osmolarity no greater than 400 mOsm/l (approximately 450 mOsm/kg). This recommendation remains till today without clear substantiation based on relevant trials. Nonetheless they have led to high feed osmolality being considered to impact adverse events -particularly gastrointestinal dysfunctions and necrotising enterocolitis (NEC)- in preterm infants. Therefore, this systematic review assessed whether there is a link between high milk feed osmolality and adverse gastrointestinal events. The conclusion is clear: no consistent evidence was found that feed osmolality in the range of 300-500 mOsm/kg is associated with adverse gastrointestinal symptoms, including NEC, in neonates.

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