Abstract: OBJECTIVE： To evaluate safety of lactose-N-tetrasaccharide (LNT) according to national food safety standards. METHODS： Acute oral toxicity test was performed using the limit method. Twenty ICR mice were administered 20 g/kg of LNT via gavage once，and the toxic effects were observed for two consecutive weeks. Bacterial reverse mutation test： Five histidine-deficient Salmonella Typhimurium strains (TA97a，TA98， TA100， TA102， and TA1535) were used， and two tests were conducted with and without S₉. For the mammalian erythrocyte micronucleus test， ICR mice were administered LNT twice via gavage at a maximum dose of 5.0 g/kg，with medium and low doses of 2.5 and 1.25 g/kg，respectively，over 30 hours. A solvent control group and a positive control group were also included. For the in vitro chromosomal aberration test， Chinese hamster lung (CHL) cell line was used，and three concentrations (0.8，2.0，and 5.0 mg/mL) were set up with and without S₉. A DMEM negative control and a positive control group were also included. A 90-day oral toxicity test was conducted with three dosage groups (2.5，5.0，and 10.0 g/kg) and a solvent control group to observe sub-chronic toxicity in SD rats. RESULTS： The acute oral toxicity test showed that the LD₅₀ of LNT in mice was greater than 20 g/kg; all three mutagenicity tests were negative. In the 90-day oral toxicity test， no significant abnormalities were observed in female rats， with a no-adverse-effect level (NOAEL) of 10.0 g/kg. Male rats showed weight gain and decreased food intake， with a NOAEL of 5.0 g/kg. CONCLUSION： Continuous gavage administration of LNT for 90 days had no adverse effects on female rats， but it caused weight gain and decreased food intake in male rats. Therefore， the safety of LNT in food applications needs to consider gender differences.

Key words: lactose-N-tetrasaccharide, acute oral toxicity test, genotoxicity test, 90-day oral toxicity test