Young 1987.

Methods	RCT, single‐centre, 2‐arm, parallel design
Participants	Total number of randomized participants: 51 Inclusion criteria People with severe head injury: primary site of injury was the brain Exclusion criteria Brain‐dead within 4 days of entering the study, or whose families decided to withdraw consent within 5 days Primary diagnosis Severe head injury Baseline characteristics EN group Age, mean (SD): 34.0 (± 2.92) years Gender, M/F: 22/6 APACHE II: not reported PN group Age, mean (SD): 30.3 (± 2.67) years Gender M/F: 20/3 APACHE II: not reported Country: USA Setting: medical centre
Interventions	EN group n = 28; some early participant loss but study authors do not report to which group these participants belonged. 11 participants did not tolerate tube feedings and were switched to PN group; used ITT analysis Details: nasogastric tube feeding, started as soon as feeding tube in place. Feeding assumed to be for duration of study (i.e. 18 days). Target rate of delivery set at 1.75 x Harris Benedict BEE and 1.5 g protein/kg bodyweight/day. Formula consisted of Traumacal (1.5 calories/mL and 22% protein, 40% fat, and 38% carbohydrate) or Ensure Plus (1.5 calories/mL and 14.7% protein, 32% fat, and 53.3% carbohydrate). Participants given metoclopramide 10 mg/6 hours to stimulate gastrointestinal motility. No participant was treated with corticosteroids Cumulative intake of protein, mean (SEM): 1.35 (± 0.12) g/kg/day PN group n = 23; some early participant loss but study authors did not report to which group these participants belonged; use of ITT analysis Details: feeding commenced within 48 hours of randomization. Feeding assumed to be for duration of study (18 days); however, participants were given EN once bowel sounds were present and GRV < 100 mL every 2 hours. Target rate of delivery set at 1.75 x Harris Benedict BEE and 1.5 g protein/kg bodyweight/day. Formula consisted of sterile AA/dextrose solutions, multi‐vitamins, trace elements, and IV lipids. 17% calories as protein, 41% as fat, 42% dextrose. No participant was treated with corticosteroids Cumulative intake of protein, mean (SEM): 0.91 (± 0.09) g/kg/day
Outcomes	Caloric intake and nitrogen balance Serum protein levels Anthropometry Immunity profile Complications (infection, pneumonia (diagnosed by symptoms of elevated WBC count, increased premature cells, elevated temperature, positive sputum culture, visual evidence of infiltrate) Aspiration pneumonia Aspiration pneumonitis Urinary tract infection Septicaemia (diagnosed by symptoms of fever, positive blood cultures, increased WBC count, no hypotension) Septic shock (diagnosed by additional symptoms of increased cardiac output, decreased systemic vascular resistance) Diarrhoea Mortality
Notes	Funding/declarations of interest: not reported Study dates: not reported Note: we assumed that study participants were in the ICU, although study authors did not report this in the paper.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Described as randomized but no additional details
Allocation concealment (selection bias)	Unclear risk	No details
Blinding of participants and personnel (performance bias) All outcomes	High risk	No details and we assumed that there were no attempts to blind personnel
Blinding of outcome assessment (detection bias) All outcomes (except mortality)	Unclear risk	No details
Blinding of outcome assessment (detection bias) Mortality	Low risk	Lack of blinding unlikely to influence outcome data for mortality
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	7 participants were entered into the study but due to exclusion criteria were excluded from analysis, included 5 deaths within 4 days. Study authors did not report to which group these participants belonged
Selective reporting (reporting bias)	Unclear risk	Clinical trials registration or prospectively prepared protocol not reported; not feasible to assess risk of reporting bias
Baseline characteristics	Low risk	Appeared comparable
Other bias	Unclear risk	Participants in PN group received more calories until the 9th day of study, and 11 EN participants required PN

AA: amino acid; ACCP: American College of Chest Physicians; ADL: activities of daily living; APACHE II: Acute Physiology and Chromic Health Evaluation II; ARDS: acute respiratory deficiency syndrome; ASA: American Society of Anesthesiologists; ATI: Abdominal Trauma Index; BEE: basal energy expenditure; BMI: body mass index; COPD: chronic obstructive pulmonary disease; CT: computed tomography; DNR: do not resuscitate; EN: enteral nutrition; F: female; GCS: Glasgow Coma Scale; GRV: gastric residual volume; HCN: high calorie nutrition; ICU: intensive care unit; iEN: immuno‐enteral nutrition; ISS: Injury Severity Score; ITT: intention‐to‐treat; IQR: interquartile range; IV: intravenous; LOS: length of stay; M: male; n: number of participants; NICU: neuro‐intensive care unit; NIHR: National Institute of Health Research; NPC: non‐protein calorie; NRS: nutritional risk score; PN: parenteral nutrition; RCT: randomized controlled trial; RIFLE: scoring system for acute kidney injury, risk, injury, failure, loss, end‐stage renal disease; SAPS: Simplified Acute Physiology Score; SCCM: Society of Critical Care Medicine; SD: standard deviation; SF‐36: 36‐item Short Form; SEM: standard error of the mean; SIRS: systemic inflammatory response syndrome; SOFA: Sequential Organ Failure Assessment; TBI: traumatic brain injury; TEN: total enteral nutrition; TPN: total parenteral nutrition; VAP: ventilator‐acquired pneumonia; WBC: white blood cell.