Rice flour, breath hydrogen, and malabsorption

In contrast to the incomplete intestinal absorption of many dietary carbohydrates in healthy humans, it has been suggested that rice flour is completely absorbed. The aims of this study were (a) to confirm efficient absorption of rice flour in healthy individuals, (b) to evaluate a "rice breath hydrogen (H2) test" in the investigation of patients with suspected malabsorption, and (c) to compare H2 results with quantitative fecal fat excretion. The test meal consisted of 100 g of carbohydrate in the form of rice pancakes. End expiratory breath samples were collected at 30-min intervals over 8 h and the H2 concentration was analyzed by gas chromatography. Three-day stool fat collections were performed on a 70-g fat intake. The results of the experiment indicated that healthy controls (n = 23) produced minimal H2 [mean increase (delta) +/- SE] = 6.9 +/- 1.4 parts per million (ppm). Patients with pancreatic disease produced 43.2 +/- 8.0 ppm. Complete or partial correction was achieved in each of 6 subjects with oral pancreatic supplements. Twenty-two patients with a variety of small bowel diseases produced a mean increase of 73.2 +/- 21.4 ppm. Breath H2 excretion was maximal in patients with bacterial overgrowth. Disease controls (n = 10) with diarrhea of colonic origin did not produce significant H2. The sensitivity of the rice-breath H2 test compared favorably with quantitative fecal fat excretion. Within individuals, there was a lack of correlation between breath H2 data (an index of CHO malabsorption) and daily stool weight that reflects the presence or absence of diarrhea. This lack of correlation supports the concept that the endogenous microflora salvage considerable quantities of unabsorbed carbohydrate.