BACKGROUND: Nutritional depletion has been related to low glutamine levels in plasma and gut mucosa. This study was set up to investigate the effects of glutamine-enriched total parenteral nutrition on intestinal morphology and permeability. METHODS: Twenty-three depleted patients were randomized and after stabilization baseline measurements were performed. Plasma glutamine concentrations, gut morphology (including proliferation and lymphocyte markers) and intestinal permeability were measured. After administration during 8-10 days of a glutamine enriched total parenteral nutrition or an isonitrogenous control solution the measurements were repeated. RESULTS: No significant changes in glutamine concentrations, intestinal permeability, mucosal morphology or gut mucosal inflammation were observed between groups. CONCLUSIONS: Glutamine enriched total parenteral nutrition in a depleted patient population does not result in improvements in gut morphology and gut barrier function.