In man, fiber is mainly degraded in the large intestine by the bacterial flora. Many of the effects of fiber on stool output arise from this degradation. The main products of fiber fermentation are short chain fatty acids (SCFAs) including acetate, propionate and butyrate, which are the major anions in the colon. Bacteria utilize SCFAs and proliferate, absorbing water from the colonic epithelium in the course of their metabolism, and thus decrease the free water content in the lumen (11). The SCFAs that are not utilized by the bacteria are largely absorbed by the colon (12). Their transepithelial transport is associated with stimulation of sodium transport from the colon in several species including human (13-15). This effect may be particularly important in acute diarrhoeal diseases where purging, and associated reduced food intake might deplete the colon of SCFAs leading to colonic dysfunction (16, 17). Thus, luminal SCFAs levels in the colon might influence the clinical course of acute diarrhoeal diseases. SCFAs have also been shown to be clinically important in one diarrhoeal disease in animal -transmissible gastroenteritis of swine (18). Animals infected with the virus develop acute enteritis with marked fluid loss from the small intestine. Young animals develop severe diarrhoea as their colonic mucosa is incapable of absorbing fluid, whereas older infected animals has been shown to have increased colonic absorption by about six-folds over the controls. This compensatory response prevents severe diarrhoea and is related to the development of colonic fermentation with the production of SCFAs.