Safety evaluation of lactulose syrup in rats

The safety of lactulose to be used in infant milk food formula as a bifidog enic factor was assessed. Lactulose syrup (50%) was administered intragastr ically to groups of male and female rats (Wistar - CFT strain, 50g), at dos es of 2, 4, 8, 12, 24 and 36 g/kg body weight/day in split doses for 20 day s. A control group of rats received lactose solution at similar levels. The general condition of animals, their behaviour, food consumption and mortal ity if any, were recorded. The LD50 values and maximum tolerated dose were calculated. The computed LD50 values for male and female rats were >31g and >21g/kg body weight and the maximum tolerated doses were 18 g and 10 g/kg body weight, respectively. Concentration greater than these caused transien t diarrhoea, which disappeared within 5 h of feeding of lactulose. Treatmen t had no effect on food consumption, growth rate or behaviour and no mortal ity was observed In any of the groups. The study indicated that incorporati on of lactulose at 0.5% in infant formula, as a bifidogenic factor, did not induce any adverse effects on rats.