Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote, "Randomisation was simple and unadjusted and was performed using sequential numbers generated at the computer centre of the NICU"
Allocation concealment (selection bias)	Low risk	Quote, "The allocations were sealed in opaque, sequentially numbered envelopes"
Blinding of participants and personnel (performance bias)	Low risk	Quote, "The supplements were prepared by personnel on the breast milk team following the instructions in the sealed envelope. These individuals were the only personnel who were aware of the group assignments, and they were not involved in the care of the infants"
Blinding of outcome assessment (detection bias)	Low risk	Quote, "The supplements were prepared by personnel on the breast milk team following the instructions in the sealed envelope. These individuals were the only personnel who were aware of the group assignments, and they were not involved in the care of the infants"
Incomplete outcome data (attrition bias)	Low risk	7/278 dropped out. The intervention and the control group were fairly similar
Selective reporting (reporting bias)	Low risk	Authors seems to report all the outcomes mentioned in the analysis plan
Other bias	Low risk	No other bias was noted