Patients with mild cognitive impairment aged 50-80 years old were recruited in Shiyan City, Hubei Province, and divided into intervention group and placebo group. They were given yeast β-glucan capsules and starch capsules, respectively, for 6 months, in order to explore whether yeast β-glucan can improve cognitive function of patients with mild cognitive impairment by regulating gut microbiota and its metabolites.

Inclusion Criteria:

• 1. Aged 50-80 years;
• 2. Permanent residents of Shiyan City;
• 3. Meet the diagnostic criteria of MCI:
• 4. Willing to cooperate in completing questionnaire survey and clinical examination, and sign informed consent;
• 5. Did not participate in other clinical trials in the past 3 months.

Exclusion Criteria:

• 1. Alcohol or drug abuse;
• 2. Patients with neurological diseases that may cause cognitive dysfunction, including cerebrovascular diseases, stroke, brain tumors, Parkinson's disease, active epilepsy, etc.;
• 3. History of severe head trauma;
• 4. Severe sensory and perceptual impairment, unable to complete the cognitive function measurement;
• 5. History of mental illness such as depression, mania, anxiety, or take psychiatric drugs;
• 6. Serious heart, lung, liver, kidney dysfunction, malignant tumors, etc.;
• 7. Suffering from autoimmune diseases;
• 8. Trauma, spinal injury or any disease that may affect the motor function of the limb;
• 9. Recent infectious diseases, acute gastrointestinal diseases;
• 10. Take antibiotics, probiotics, prebiotics or biostime products within the last 1 month.

Triple blind, the unique codes of the intervention and placebo are known only to the person in charge of the intervention manufacturer (Anginute), not to the study implementors, investigators, subjects, data collectors and analysts, and are only unblinded by the manufacturer after the study is completed.