Effect of Vitamin D and Folic Acid on Mild Cognitive Impairment

Inclusion Criteria: * Aged 50 to 70 years old. * Derived from the established elderly chronic disease and health cohort. * Meet the diagnostic criteria for Mild Cognitive Impairment (MCI) (e.g., indicated by specific cut-off scores on the MoCA adjusted for education level). * Volunteered to participate, able to cooperate with the cognitive assessments, and signed the informed consent form. Exclusion Criteria: * Diagnosis of Alzheimer's disease, other types of dementia, or severe psychiatric disorders (e.g., severe depression, schizophrenia). * History of severe neurological diseases (e.g., stroke, brain tumor, brain trauma) that may affect cognitive function. * Severe visual or hearing impairments that prevent the completion of cognitive tests. * Patients with liver diseases (e.g., hepatitis, liver cirrhosis) or kidney diseases (e.g., nephritis, kidney stones, renal failure). * Patients with hypercalcemia (serum calcium concentration \> 10.5 mg/dl). * Patients with severe anemia, severe malnutrition, or abnormal thyroid function. * Current use or use within the past 3 months of cognition-improving drugs, Vitamin D, or Folic Acid supplements, and unwilling to undergo a 3-month washout period prior to the intervention.