D-Tagatose is a stereoisomer of D-fructose which is poorly absorbed in the small intestine and may, therefore, have potential as a reduced calorie bulk sweetener. However, one of the major limitations is the use of malabsorbed sugars is that their consumption may be associated with gastric discomfort. This is due to the osmotic impact of the sugar molecules remaining in the gut lumen for a prolonged period. We have performed a series of studies in which gastrointestinal symptoms have been recorded after the consumption of 29 or 30 g of D-tagatose. Nausea and diarrhea were reported with an incidence of 15.1 and 31.5%, respectively, in 73 healthy young male subjects in a screening study. Increased flatulence after D-tagatose was frequently reported in all the studies and the flatulence did not decline during a 15-day period with intake of 30 g in one dose daily. In most cases, symptoms were reported as light or moderate. However, the results suggest that 30 g taken at one time may be above the dose which should be recommended for ordinary use.