Arabinoxylan (AX) is the major component of dietary fiber in the cereal grains that make up a large proportion of our diet. However, the physiologic effect of AX is unknown.The objective of this study was to determine whether AX improves postprandial glucose and insulin responses in healthy humans.AX-rich fiber was extracted from the byproduct of wheat-flour processing. Three isoenergic breakfasts, comprising bread, margarine, and jam, had 75 g available carbohydrate, 10 g protein, and 14 g fat and contained 0, 6, and 12 g AX-rich fiber, respectively. Fourteen healthy subjects consumed the 3 breakfast meals in random order on 3 mornings >/=3 d apart after an overnight fast. Blood was taken from the subjects at regular intervals over 2 h and was analyzed for glucose and insulin. The palatability of bread containing AX-rich fiber was compared with that of a control bread.Compared with the control meal containing 0 g AX-rich fiber, the peak postprandial glucose concentration after meals containing 6 and 12 g AX-rich fiber was significantly lower (6. 3 +/- 1.3 compared with 7.2 +/- 1.0 mmol/L, P < 0.01; 5.9 +/- 0.9 compared with 7.2 +/- 1.0 mmol/L, P < 0.001, respectively). The incremental area under the curve (IAUC) for glucose was 20.2% (95% CI: 5.8%, 34.7%; P < 0.01) and 41.4% (25.9%, 56.8%; P < 0.001) lower, whereas IAUC for insulin was 17.0% (2.0%, 32.1%; P < 0.05) and 32. 7% (18.8%, 46.6%; P < 0.001) lower, respectively. Bread containing AX-rich fiber was as pala as 50% whole-wheat bread when evaluated with sensory analysis by 30 volunteers.Postprandial glucose and insulin responses were improved by ingestion of AX-rich fiber. Further research is required to determine whether AX-rich fiber is of benefit to people with type 2 diabetes.