The objectives of this study were to investigate the effects of an excess of xylitol on nitrogen balance and glucose metabolism in parenterally fed rats. Female Sprague-Dawley rats (200-250 g, n = 17) were catheterized for total parenteral nutrition and then randomized into two groups based on subsequent diet. The two diets used were isonitrogenous (1.5 g of nitrogen per kilogram per day) and isocaloric, with half the calories (125 kcal/kg per day) being derived from lipid (125 kcal/kg per day) and the other half from either glucose or xylitol (125 kcal/kg per day). The rats were fed a half-strength total parenteral nutrition diet for the day after surgery and a full-strength total parenteral nutrition diet for the following 4 days. Urines were collected daily for the determination of nitrogen balance. On day 5, the rats were given a 7- to 8-hour infusion of 6.6-d2 glucose (6 mg/h and 2-d1 glucose (12 mg/h). At the conclusion of the isotope infusion period, the rats were killed and blood was collected. Urine output was increased by 22% per day in the xylitol-treated rats, and they excreted 46.5 mmol of xylitol per liter per kilogram per day (7.1 g/kg per day, approximately 22.7% of dose). The xylitol group lost weight, had poorer nitrogen balance (341 +/- 31 vs 83 +/- 29 mg/kg per day [mean +/- standard error of the mean], p < .05), and developed fatty livers. Analysis of the liver fat distribution pattern indicated that the source of the excess hepatic lipid was dietary fat.(ABSTRACT TRUNCATED AT 250 WORDS)