Beier‐Holgersen 1996.

Methods	Randomised double‐blind controlled trial No information provided about duration of study
Participants	60 participants (30 in each group); mainly colorectal surgery (87%) Bowel resection Route of feeding: nasoduodenal Median age: 66.5 years (range 27‐93) (intervention group), 61.5 years (range 27‐80) (control group) Male:Female 18:12 (intervention group), 20:10 (control group)
Interventions	Intervention group: received a nutrition supplement of Nutridrink (orange flavour) within four hours postoperatively. Nutridrink contained 150 kcal/100 mL and 5 g protein/100 mL. Nutritional supplement given until fourth day. Control group: received placebo (water with orange flavour, no energy, vitamins or trace elements) during same period.
Outcomes	Wound infection, intraabdominal abscess, anastomotic leakage, mortality, postoperative complications (pneumonia, dehiscence, pulmonary failure), LoS, adverse events (nausea, vomiting).
Notes	Country of study: Denmark
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information provided
Allocation concealment (selection bias)	Unclear risk	No information provided
Blinding of participants (performance bias) All outcomes	Low risk	Reported as double‐blinded. Use of an identical placebo flavoured orange. Groups received different volume of drink (4000 mL vs. 4700 mL). Unlikely to unblind.
Blinding of personnel (performance bias) All outcomes	Low risk	Reported as double‐blinded. Nutridrink or placebo in identical containers was administered by the nursing staff.
Blinding of outcome assessor (detection bias) ‐ wound infections	Low risk	The principal investigator saw the patients every day during their stay in the ward, and all complications were recorded by the same investigator. The randomisation code was not broken until all results were available and all patients had been followed up for 30 days after surgery and all complications classified.
Blinding of outcome assessor (detection bias) ‐ intraabdominal abscesses	Low risk	The principal investigator saw the patients every day during their stay in the ward, and all complications were recorded by the same investigator. The randomisation code was not broken until all results were available and all patients had been followed up for 30 days after surgery and all complications classified.
Blinding of outcome assessor (detection bias) ‐ postoperative complications e.g. acute myocardial infarction, thrombosis or pneumonia	Low risk	The principal investigator saw the patients every day during their stay in the ward, and all complications (pneumonia, dehiscence, pulmonary failure, myocardial infarction) were recorded by the same investigator. The randomisation code was not broken until all results were available and all patients had been followed up for 30 days after surgery and all complications classified.
Blinding of outcome assessor (detection bias) ‐ anastomotic leakage/dehiscence	Low risk	The principal investigator saw the patients every day during their stay in the ward, and all complications were recorded by the same investigator. The randomisation code was not broken until all results were available and all patients had been followed up for 30 days after surgery and all complications classified.
Blinding of outcome assessor (detection bias) ‐ mortality	Low risk	The principal investigator saw the patients every day during their stay in the ward, and all complications were recorded by the same investigator. The randomisation code was not broken until all results were available and all patients had been followed up for 30 days after surgery and all complications classified.
Blinding of outcome assessor (detection bias) ‐ adverse events (e.g. nausea, vomiting, abdominal distention, aspiration, tube blockage and any other adverse events	Low risk	(Nausea, vomiting) The principal investigator saw the patients every day during their stay in the ward, and all complications were recorded by the same investigator. The randomisation code was not broken until all results were available and all patients had been followed up for 30 days after surgery and all complications classified.
Blinding of outcome assessor (detection bias) ‐ length of hospital stay	Low risk	The principal investigator saw the patients every day during their stay in the ward, and all complications were recorded by the same investigator. The randomisation code was not broken until all results were available and all patients had been followed up for 30 days after surgery and all complications classified.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Less than 10% missing data.
Selective reporting (reporting bias)	High risk	No protocol available. The outcome LoS was reported in results but not explicitly stated as an outcome of interest in methods (just PO course).