The Characteristics of Gut Microbiota in Patients With Sarcopenia and the Development of Probiotics

Inclusion criteria 1. Sarcopenia patient group * Individuals aged 65 to 90 years * Meet the diagnostic criteria for sarcopenia based on the 2019 Asian Working Group for Sarcopenia (AWGS) guidelines: * Low appendicular skeletal muscle mass * DEXA: \<7.0 kg/m² (men), \<5.4 kg/m² (women) * BIA: \<7.0 kg/m² (men), \<5.7 kg/m² (women) * Low muscle strength * Handgrip strength: \<28 kg (men), \<18 kg (women) or * Low physical performance * 6-meter walk speed \<1.0 m/s * 5-chair stand test ≥12 seconds * Short Physical Performance Battery (SPPB) score ≤9 * Voluntarily agree to participate in the clinical study and sign the informed consent form 2. Older adult control group * Individuals aged 65 to 90 years * Voluntarily agree to participate in the clinical study and sign the informed consent form 3. Young adult control group * Individuals aged 20 to 50 years * Voluntarily agree to participate in the clinical study and sign the informed consent form Exclusion criteria * Individuals currently under treatment for severe diseases of the cardiovascular, immune, respiratory, gastrointestinal/hepatic and biliary, renal/urinary, neurological, psychiatric systems, infectious diseases, or malignant tumors (Exception: skin tumors other than melanoma are excluded; cancer survivors may participate if more than 5 years have passed since complete remission). * Individuals who have difficulty performing independent activities of daily living due to musculoskeletal or neurological diseases, or cognitive impairment (e.g., those with spinal disorders requiring surgery or having walking limitations). * Individuals who regularly consume alcohol according to WHO daily intake standards (≥ 40 g/day for men, ≥ 20 g/day for women). * Heavy smokers (≥ 20 cigarettes/day). * Individuals with AST (GOT) or ALT (GPT) levels ≥ 3 times the upper limit of normal established by the testing institution. * Patients with uncontrolled hypertension (systolic blood pressure ≥ 140 mmHg or diastolic blood pressure ≥ 90 mmHg, measured after the subject has rested for 10 minutes). * Patients with uncontrolled diabetes mellitus (HbA1c \> 7.0%). * Individuals with TSH ≤ 0.1 μIU/mL or ≥ 10 μIU/mL. * Individuals deemed unsuitable for other reasons at the discretion of the investigator.