A cognitive function-improving agent containing one or both of Bifidobacterium breve FERM BP-11175 and a culture of Bifidobacterium breve FERM BP-11175 as an active ingredient for administration to a subject who has not developed dementia is provided.

Disclosed are a yoghurt for regulating intestinal tract, preparation method therefor, and use thereof, where the yogurt is prepared from raw materials comprising the following parts by weight: 90-97 parts of raw milk, Lactobacillus gasseri of (0.7-5)×10.sup.8 CFU/100 g raw milk, Streptococcus thermophilus of (0.1-9)×10.sup.10 CFU/100 g raw milk, Lactobacillus bulgaricus of (0.1-9)×10.sup.10 CFU/100 g raw milk, Lactobacillus acidophilus of (0.5-7)×10.sup.8 CFU/100 g raw milk, Lactobacillus plantarum of (0.5-7)×10.sup.8 CFU/100 g raw milk, Lactobacillus paracasei of (0.1-9)×10.sup.7 CFU/100 g raw milk, and other probiotics, and prebiotics such as inulin. The yogurt may regulate the balance of intestinal flora and prevent constipation and gestational diabetes in overweight and/or obese pregnant women during the gestation period.