Inclusion Criteria:  The subject is between 50-95 years old. The subject is clinically diagnosed with Alzheimer's disease, and it meets the diagnostic criteria of Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDB) or National Institute on Aging and Alzheimer's Association (NIAAA). The subject's MMSE score is between 10-25. The subject's CDR score is 0.5, 1, or 2. The subject can cooperate to perform cognitive function tests. The subject who have dependable caregivers who can record the compliance of taking probiotics and any physical conditions. The subject or family members have signed the informed consent form.  Exclusion Criteria:  The subject is shown to have cerebrovascular disease by computer tomography. The subject has dementia caused by other reasons, such as brain trauma, tumor, infection, epilepsy, etc. The subject has used immunosuppressant drugs, steroids, T cell inhibitor ointments or received chemotherapy within 2 weeks. The subject has consumed probiotic-related products (probiotic powder, yogurt or other fermented foods) within the past 1 month. The subject has participated in clinical trials of other dementia medications in the past 1 month. The subject is assessed for dementia caused by vitamin B12 deficiency or thyroid abnormalities. The subject suffers from mental illness, severe depression, schizophrenia, drug addiction, and alcohol addiction. The subject has Parkinson's disease. The subject is assessed to have severe metabolic dysfunction, liver and kidney dysfunction.