Nutritional effects have traditionally focused on outcomes, such as nitrogen balance, wound healing, or muscle strength. Little emphasis has been placed on how biochemical or physical improvements translate into functional changes as perceived by the patient. Because glutamine (GLN)-supplemented nutrition promotes protein synthesis and improves nitrogen balance, we assessed the mood of individuals participating in a randomized controlled blinded trial receiving GLN solutions. Patients (n = 23) undergoing marrow transplantation were randomized by the research pharmacist to receive either standard total parenteral nutrition (TPN) (control) or GLN-containing TPN (40 g of glutamine total). The solutions were isocaloric and isonitrogenous and were administered until the patient was eating 50% of estimated requirements. Before TPN and on admission to the hospital, the patient completed the Profile of Mood States questionnaire, a standardized test quantifying the degree of tension, depression, anger, vigor, fatigue, and confusion. The patient completed the questionnaire again at the end of TPN near discharge. The tests were scored and the change from baseline for each mood for both groups of patients was calculated at the completion of TPN. The scores for vigor in the control group (delta scores) decreased over the course of hospitalization as would be expected with a serious illness. The group receiving glutamine TPN, however, essentially showed little change in vigor from baseline and the delta score was significantly different from the control group (delta vigor score -0.85 +/- 2.1 in the glutamine group vs. -5.90 +/- 1.7 in the control group; p = .07).(ABSTRACT TRUNCATED AT 250 WORDS)