Breath hydrogen measurement was used to assess the carbohydrate absorption from white wheat flour in 18 subjects, to determine if malabsorption of this type of carbohydrate could cause symptoms similar to those of lactose malabsorption. Breath hydrogen increased significantly in 17 subjects after they had eaten macaroni or bread from white flour but not sucrose, low-gluten wheat flour, or rice flour, indicating incomplete absorption of the starch rather than small bowel bacterial overgrowth. The interaction of wheat starch with gluten was thought to be a possible cause