Kim 2015.

Study characteristics
Methods	Parallel randomised controlled trial, multi‐centre, stratification by infant sex and birth weight
Participants	Inclusion criteria preterm infants born ≤ 33 weeks' gestational age with birth weight 700–1500 g who were enterally fed human milk in the neonatal intensive care unit), appropriate intrauterine growth and maternal intent to provide breast milk during the study Exclusion criteria enteral feeds not started within 21 days of life severe congenital anomalies expectant transfer to another facility 5 minute Apgar < 5 severe intraventricular haemorrhage (grade 3 or 4) mechanical ventilation major abdominal surgery severe asphyxia necrotising enterocolitis any use of probiotics or postnatal corticosteroids Setting: 14 neonatal intensive care units from across the USA Study date: not reported
Interventions	Intervention: bovine based liquid human milk fortifier containing 1.66 g extensively hydrolysed protein added to 100 mL EBM (n = 66) Control: bovine based human milk fortifier containing 1 g intact protein added to 100 mL EBM (n = 63) Calorie content: non‐isocaloric, providing 30 kcal (intervention) vs 14 kcal (control) energy added to 100 mL EBM (110 kcal vs 99 kcal in fortified EBM, 11% difference) Start of intervention: within 72 hours after the infant had reached an intake of ≥ 100 mL/kg/day of human milk Mean age at study day 1: 12.8 days (SE 0.6) in intervention group and 12.3 days (SE 0.7) in control group End of intervention: 29 days or hospital discharge
Outcomes	Primary outcome weight gain Secondary outcomes length and head circumference gain blood cell counts serum blood biochemistries feeding tolerance morbidity respiratory outcomes adverse events
Notes	Conflict of interest: JHK is on the speakers' bureaus for Abbott Nutrition, Mead Johnson Nutrition, Nestle Nutrition, Nutricia and Medela. JHK and RS are on the medical advisory board for Medela. Source of funding: Abbott Nutrition funded the study. Note that the human milk fortifier used in the intervention group was liquid; therefore, the added protein concentration was converted to gram per 100 mL of fortified EBM in this review.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation schedules were computer generated using a (quote:) "pseudorandom permuted blocks algorithm". A separate computer generated randomisation schedule was produced for twins to ensure that eligible twins were both assigned to the same product. The randomisation block was stratified by infant birth weight (700–1000 g and 1000–1500 g) and sex.
Allocation concealment (selection bias)	Low risk	Sealed envelopes contained the treatment group assignment.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Study was unblinded.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Study was unblinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All infants accounted for, and reported by intention to treat, the attrition rate was 12% in the intervention group and 12.5% in the control group.
Selective reporting (reporting bias)	Unclear risk	Insufficient information.
Other bias	Unclear risk	Trial was sponsored by manufacturer, the role of whom was not described further.