Clinical trial, active comparator, cross over, randomised. In total, 12 adults with an ileostomy will be randomised to a sequential 4 weeks intervention with different qualities and sources of protein wish 2-week washout periods. Primary outcome: Ileostomy output.

Patients with an ileostomy may be dehydrated and have nutritional deficiencies secondary to malabsorption of fluid, electrolytes, and nutrients. In this randomised, double blinded, crossover intervention study we aim to investigate how different protein sources affect intestinal absorption in patients with an ileostomy and intestinal insufficiency. Three oral solutions with different protein sources (hydrolysed whey, whey, and casein) will be administered in three different four-week intervention periods. The results will facilitate improved counselling and treatment of patients with an ileostomy.

Inclusion Criteria:

• Adult (≥ 18 years old), male or female patients with an ileostomy and intestinal insufficiency
• Episodical or chronic sodium depletion defined by two urine samples with sodium levels ≤ 20 mmol/L, sampled with at least 28 days apart
• Six months or more after most recent bowel surgery
• If inflammatory bowel disease, no clinical signs of activity (any treatment allowed except systemic steroids > 10 mg/day)

Exclusion Criteria:

• Parenteral nutrition or intravenous fluid support ≥ 4000 mL/month
• Ongoing infection (C-reactive protein above 8 mg/L or core temperature >38.0°C)
• Self-reported intolerance to dairy products, including lactose intolerance
• Inability to understand Danish or the trial procedures
• Known or anticipated pregnancy
• Known severe renal insufficiency (eGFR < 20 mL/min)
• Known diabetes mellitus (HbA1c ≥ 48 mmol/mol (6.5%))
• Pacemaker, cochlear implants, or other electrical implants excludes the participants from BIA-measurements and measurements of GITT with 3D-Transit capsules, but not the remaining investigations
• Known intestinal stenosis or parastomal hernia excludes measurements of GITT with 3D-Transit capsules, but not the remaining investigations
• Abdominal diameter > 140 cm, or planned MR scan four weeks following participation excludes measurements of GITT with 3D-Transit capsules, but not the remaining investigations

Anonymised data or selections herof will be shared upon specific agreements and with researchers who have legitimate causes, following contact to the PI

upon request, after publication

contact to PI

Production in separate facility, randomisation key kept by third party