Evaluate the effectiveness and safety of Bifidobacterium longum subsp. infantis BI45 as a food supplement compared to a placebo in improving intestinal and immune functions in healthy adults.

Inclusion Criteria:

1. Willing to undergo 3 follow-up visits during the intervention period Be willing to provide blood, urine and stool samples 2 times during the intervention period
2. Willing to self-administer probiotic or placebo once a day during the intervention period
3. Good eyesight, can read and write, can wear glasses
4. Have good hearing and be able to hear and understand all instructions during the intervention

Exclusion Criteria:

1. Digestive diseases, mainly gastrointestinal diseases (celiac disease, ulcerative colitis, Crohn's disease)
2. Have a serious neurological condition (epilepsy, stroke, severe head trauma, meningitis in the last 10 years, brain surgery, brain tumor, prolonged coma - not including general anaesthesia)
3. Have received/are receiving treatment for the following mental disorders: alcohol/drug/substance abuse dependence, schizophrenia, psychosis, bipolar disorder
4. Take medication for depression or low mood Internal organ failure (heart, liver or kidney failure, etc.)
5. Have received radiation or chemotherapy in the past
6. Have undergone a general anesthesia procedure/procedure within the past three years, or plan to undergo a general anesthesia procedure/procedure within the next 3 months during this trial period
7. Have had hepatitis (hepatitis B, hepatitis C), HIV or syphilis in the past