Background: Although standard glucose-based oral rehydration therapy corrects the dehydration caused by cholera, it does not reduce the diarrhea. Short-chain fatty acids, which are produced in the colon from nonabsorbed carbohydrates, enhance sodium absorption. We conducted a study to determine the effects of an orally administered, nonabsorbed starch (i.e., one resistant to digestion by amylase) on fecal fluid loss and the duration of diarrhea in patients with cholera. Methods: We randomly assigned 48 adolescents and adults with cholera to treatment with standard oral rehydration therapy (16 patients), standard therapy and 50 g of rice flour per liter of oral rehydration solution (16 patients), or standard therapy and 50 g of high-amylose maize starch, an amylase-resistant starch, per liter of oral rehydration solution (16 patients). The primary end points were fecal weight (for every 12-hour period during the first 48 hours after enrollment) and the length of time to the first formed stool. Results: The mean (±SD) fecal weights in the periods 12 to 24 hours, 24 to 36 hours, and 36 to 48 hours after enrollment were significantly lower in the resistant-starch group (2206±1158 g, 1810±1018 g, and 985±668 g) than in the standard-therapy group (3251±766 g, 2621±1149 g, and 2498±1080 g; P=0.01, P= 0.04, and P=0.001, respectively). From 38 to 48 hours after enrollment, fecal weight was also significantly lower with the resistant-starch therapy than with the rice-flour therapy (985±668 g vs. 1790±866 g, P = 0.01). The mean duration of diarrhea was significantly shorter with the resistant-starch therapy (56.7±18.6 hours) than with standard therapy alone (90.9±29.8 hours, P=0.001) or the rice-flour therapy (70.8±20.2 hours; P=0.05). Fecal excretion of starch was higher with the resistant-starch therapy (32.6±30.4) than with the standard therapy (11.7±4.1 g, P=0.002) or the rice-flour therapy (15.1±8.4 g, P=0.01). Conclusions: The addition of a resistant starch to oral rehydration solution reduces fecal fluid loss and shortens the duration of diarrhea in adolescents and adults with cholera. (C)2000, Massachusetts Medical Society.