Inclusion Criteria:  Patients who is suffering from Mild Cognitive Impairment. Clinical Dementia Rating (CDR) 0.5. Age 40-80 and willing to sign the Informed Consent. Education level is above the junior high school level. Healthy control who is eligible judged by PI.  Exclusion Criteria:  Patients on antibiotics within the preceding one month. Patients using of other probiotic products (sachet, capsule or tablet) within the preceding two weeks. Have undergone surgery of liver, bladder, or gastrointestinal tract. Have current or history of inflammatory bowel disease. Have history of cancer. Known allergy to probiotics. Dementia (MMSE ≤ 23). Cognitive Impairment caused by head injury. History of cerebral apocalypse. Other possible diseases may cause cognitive impairment, such as: Parkinson's disease, cervical mass, hydrocephalus or epilepsy. Severely depressed patients (sick person health questionnaire-9 (PHQ-9) ≥ 20). Severe anxiety patients (Generalized Anxiety Dosorder 7-Item (GAD-7) ≧ 15). Undergoing medication treatment for acute illness, Organic psychosis or diagnosed as psychiatric illness within 3 months or poor control of chronic psychiatric illness. Undergoing parenteral nutrition. Not eligible judged by PI.