To evaluate the safety and efficacy of Streptococcus salivarius subsp. thermophilus ST36 in healthy adults on immune function and intestinal health.

Inclusion Criteria:

• 1) Age 18-45 years; 2) Willing to undergo 3 follow-up visits during the intervention period; 3) Willing to provide 2 blood, urine, and stool samples during the intervention period; 4) Willing to self-administer Streptococcus salivarius subsp. thermophilus ST36/placebo once daily during the intervention period; 5) Good eyesight, able to read and write, and can wear glasses; 6) Have good hearing and be able to hear and understand all instructions during the intervention;

Exclusion Criteria:

• 1) Suffering from digestive disorders, mainly gastrointestinal disorders (celiac disease, ulcerative colitis, Crohn's disease); 2) Has a severe neurological condition (epilepsy, stroke, severe head trauma, meningitis within the past 10 years, brain surgery, brain tumor, prolonged coma - excluding general anesthesia); 3) Has received/is receiving treatment for the following psychiatric disorders: alcohol/drug/substance abuse dependence, schizophrenia, psychosis, bipolar disorder; 4) Take medication for depression or low mood; 5) Suffering from internal organ failure (heart, liver, or kidney failure, etc.); 6) Radiotherapy or chemotherapy in the past; 7) Surgery/procedure under general anesthesia within the past three years, or planned to undergo a procedure/procedure under general anesthesia within the next 3 months during this trial; 8) Have had hepatitis (hepatitis B, hepatitis C), HIV or syphilis in the past.

Double(Participant, investigator)