To explore the long-term metabolic effects of acarbose in man, 6 healthy men (25 +/- 2 years; BMI: 21.6 +/- 2.7) were fed a controlled diet in a metabolic ward for 7 consecutive weeks. After an initial 3-week period to ensure a metabolic steady-state, they received 300 mg/d of acarbose (100 mg before each meal) for the remaining 4 weeks. Stool and urine collections were made over 7 d on weeks 3 and 7. Faecal excretion of water, nitrogen, carbohydrate, fat, zinc, magnesium, copper, chromium, iron, calcium and phosphorus and urinary excretion of nitrogen, urea and calcium were measured. In addition, fasting and postprandial blood glucose and insulin levels, as well as fasting triglycerides, total cholesterol, apolipoproteins (Apo) A-I, A-II, and B, zinc and copper, vitamins A, B1, B2, B6, C, and E concentrations were measured before and at the end of the acarbose period. Weight, food consumption, and water balance were not modified by acarbose. Faecal nitrogen excretion increased significantly but the nitrogen balance remained positive. Faecal excretion of carbohydrate, fat, iron and chromium were significantly increased by acarbose. Apos A-I and A-II decreased significantly. Plasma levels of vitamin B6 increased and vitamin A concentrations decreased with acarbose. This study provides new insights into the metabolic effects of acarbose with respect to nitrogen, mineral and vitamin metabolism.