At the Screening phase, 100 subjects had the Urine galactose (U-gal) test to screen 45 subjects eligible for the study and they should simultaneously meet the Inclusion and Exclusion criteria. Subjects should be fasting on the morning of testing, and then drink 300 ml full-fat milk within 3-5 minutes. Empty the urine 1 hour after drinking, and collect midstream urine 2 hours after milk-consumption for urinary galactose test with symptom scores recorded accordingly. Urine galactose (U-gal) tests positive indicating the lactase deficiency, if it is accompanied by abdominal distension, abdominal pain and other symptoms of more than 1 item; it is identified as lactose intolerance.