Rigo 2017.

Study characteristics
Methods	Parallel randomised controlled trial, multi‐centre, stratification was by centre, sex and birth weight
Participants	Inclusion criteria preterm infants (≤ 32 weeks' gestation, or ≤ 1500 g at birth), clinically stable, mothers intended to provide breast milk or donor milk during study period Exclusion criteria preterm infants had history of or current systemic, metabolic, or chromosomic disease congenital anomalies of GI tract small for gestational age (< 5th percentile) receiving steroids during study period receiving preterm formula study period Setting: neonatal intensive care unit at 11 metropolitan hospitals in France, Belgium, Germany and Switzerland and Italy Timing: April 2011 to March 2014
Interventions	Intervention: bovine based human milk fortifier containing 1.42 g hydrolysed protein added to 100 mL EBM (n = 76) Control: bovine based human milk fortifier containing 1 g hydrolysed protein added to 100 mL EBM (n = 74) Calorie content: isocaloric, providing 84.5 kcal energy per 100 mL fortified human milk Start of intervention: infants tolerating > 100 mL/kg/day of human milk for > 24 hours Median age at study day 1: 16 days (IQR 13–20) in intervention group and 17 days (IQR 13–23) in control group End of intervention: minimum of 21 days, or until discharged/medical decision to stop fortification
Outcomes	Outcomes were not specified as primary or secondary growth (weight, length and head circumference gain) protein energy status (blood urea nitrogen, prealbumin levels, urinary urea excretion) bone metabolic status (serum calcium, phosphorus, alkaline phosphatase, urinary excretion of calcium and phosphorus) stool characteristics and feeding intolerance adverse events (GI disorder, infections, metabolism and nutrition disorder, cardiac disorders, eye disorders, necrotising enterocolitis, bronchopulmonary dysplasia, sepsis and retinopathy)
Notes	Conflict of interest: authors either received research funding from Nestle Nutrition or were affiliated with Nestle Nutrition. Source of funding: Nestle Nutrition funded the study.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer generated list of random numbers was used to allocate group assignment. Minimisation algorithm with allocation ratio 1:1 and second best probability of 15% was used.
Allocation concealment (selection bias)	Unclear risk	Reported as (quote:) "Group coding was used with 2 non speaking codes per group; fortifier packaging was coded accordingly but otherwise identical in appearance". Lack of clarity, uncertain of what the quote above means.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	All study personnel (both site and sponsor based) and participants (infants' families) were blind to group assignment.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	All study personnel (both site and sponsor based) were blind to group assignment.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All infants accounted for in flow diagram, attrition rate similar between groups (only 1 infant in the intervention group and 2 infants in the intervention group were excluded due to violation of the exclusion criteria).
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.