Study	Reason for exclusion
Abrams 2014	Comparison of human milk‐based versus cow’s milk‐based protein supplementation
Barrington 2016	Comparison of human milk or formula versus milk with 100 mg/day of bovine lactoferrin powder
Berseth 2012	Unable to locate the full article
Bhat 2001	Supplementation was with a multi‐nutrient fortifier
Bishara 2017	Not a randomised trial
Boehm 1988b	No evidence of randomisation
Ditzenberger 2013	Composition of the fortifier was not clear, infants received formula when mothers milk was insufficient, and a Microlipid was added to increase caloric density.
Gathwala 2012	Supplementation was with a multi‐nutrient fortifier.
Hair 2014	The control group received supplementation.
Hayashi 1994	The fortifier contained extra carbohydrate.
Hill 1997	Studies in the abstract of podium presentations were not related to our review.
Kashaki 2018	Both groups received breast milk fortifier.
Modanlou 1986	Supplementation was with a multi‐nutrient fortifier.
Moltu 2013	The control group received supplementation.
Polberger 1997	No unsupplemented arm
Valman 1971	The intervention was either expressed human milk and breast milk substitute or evaporated milk formula.