Honey contains fructose in excess of glucose, which may lead to incomplete fructose absorption associated with abdominal symptoms and/or diarrhea. This hypothesis was investigated in 20 healthy volunteers (13 males, 7 females) with a mean (+/- SD) age of 35.9 +/- 12.1 y. Each subject drank the following aqueous solutions in random order: 20 g lactulose, 100 g honey, 50 g honey, and 35 g each of a glucose and fructose mixture. The breath-hydrogen concentration was measured every 15 min for 6 h. Semiquantitative estimates of carbohydrate malabsorption were assessed with lactose as a nonabsorbable standard. Breath-hydrogen concentrations increased by 52 +/- 6, 30 +/- 4, 20 +/- 3, and 4 +/- 1 ppm (mean +/- SEM) after each of the four test solutions, respectively. The estimated carbohydrate malabsorption was 10.3 +/- 1.8, 5.9 +/- 1.2, and 0.5 +/- 0.2 g after 100 g honey, 50 g honey, and the glucose-fructose mixture, respectively (F[2,57] = 16.05, P < 0.001). Within 10 h after the ingestion of 100 g honey, 50 g honey, and the glucose-fructose mixture, six, three and none of the volunteers, respectively, reported loose stools (chi 2 = 7.1, df = 2, P < 0.03). The results of this study suggest that carbohydrate malabsorption after ordinary doses of honey is frequent in healthy adults and may be associated with abdominal complaints. Honey may have a laxative effect in certain otherwise healthy individuals, probably because of incomplete fructose absorption.