Eleven diabetic patients: 5, type 1 and 6, type 2 received a low-fiber diet (I) during 1 week and during the next 7 days the same diet, enriched with 40 g of fiber (30.6% insoluble and 11.7% soluble components) from rice bran (II) per day. Results showed that mean fasting and postprandial serum glucose levels were reduced, but values of high fiber diet were significantly lower (p < 0.001) than that of the lower fiber diet. For all patients, the high-fiber diet increased fecal weight. This increase was due to the fiber excreted, rather than water retained. There was no relationship between the increase in fiber intake and its fecal excretion. Sucrose and raffinose were found in the bran, but not in the feces. Lactose was present in the stools of the patients receiving enriched diet.