Polberger 1989.

Study characteristics
Methods	Parallel randomised controlled trial in two neonatal units.
Participants	Inclusion criteria: birth weight < 1500 g, appropriate‐for‐gestational‐age, tolerance of complete enteral feeding (170 mL/kg/day), no obvious disease or major malformations, no oxygen therapy, and informed parental consent and acceptance of a blind trial Exclusion criteria: not stated Setting: two neonatal units of the University of Lund in Malmo and Lund Timing: not stated
Interventions	1.0 g of human milk fat per 100 mL unpasteurised human milk (maternal or term banked donor) (n = 7) versus unsupplemented human milk (n = 7). Intervention ceased when the infant reached approximately 2200 g or was breastfed. All infants were supplemented with additional vitamins, calcium lactate (30 mg/kg/day) and sodium phosphate (20 mg/kg/day). From 4 weeks, 2 mg/kg/day elemental iron was given to all infants.
Outcomes	The outcomes were not specified as primary or secondary but the following were assessed: short‐term growth parameters (weight, crown‐heel length, occipito‐frontal head circumference), intake of protein, fat, carbohydrates, energy, and electrolytes (sodium, potassium, calcium).
Notes	Conflicts of interest: no details Source of Funding: supported in part by the Swedish Medical Research Council, Grant No. B85‐ I'IX‐06259, and Stiftelsen Saniarite This study had four arms: unsupplemented versus supplemented with protein versus supplemented with fat versus supplemented with fat and protein. The analyses of the protein and combined fat and protein arms are discussed in other reviews on multi‐component and protein supplementation, respectively (Brown 2016; Kuschel 2000). Of the 34 infants enrolled in the study, 6 were withdrawn following randomisation for apnoea (n = 2), intolerance to accepting the fixed volume (n = 3) and need for intravenous therapy (n = 1).
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No details
Allocation concealment (selection bias)	Unclear risk	The study used closed envelopes without specifying if they were opaque or not.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	The study was stated to be double‐blinded, but who was blinded was not specified
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	It was not specified whether outcome assessors were blinded.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	The missing data (i.e. from 6 infants) was less than 20%. They were excluded for the following reasons: 2 had apnoea, 3 developed feeding intolerance, and 1 needed intravenous therapy. However, the authors did not report whether there were any differences between infants excluded and included in the study.
Selective reporting (reporting bias)	Unclear risk	No details were given as to which were primary and secondary outcomes, and no protocol was viewed to clarify whether the outcomes reported were the only ones collected.
Other bias	Unclear risk	The authors stated 'there was a difference in sex distribution between the groups and later analyses confirmed that this difference had no implications on the results'. However, no further details were provided as to how this conclusion was reached.