The clinical trial aims to investigate the impact of probiotic strain BL21 on sperm quality among 46 middle-aged male participants. The primary objective is to validate whether probiotic strain BL21 can effectively improve sperm quality among middle-aged male participants. Initially, participants were instructed to consume the recommended amount of probiotic powder for approximately 8 weeks. At baseline, week 4, and week 8 endpoints, semen analysis, hormone level testing, serum cytokine testing were conducted on the participants, and stool samples were collected from them.

Research has indicated that an increase in male age is independently associated with a reduction in the percentage of motile sperm and sperm with normal morphology, especially in men over 40 years old, potentially linking to a decline in fertility rates. Preclinical studies have shown that supplementation with Long Bifidobacterium can regulate immune responses, inhibit tissue inflammatory factors, and the predictive functions of the gut microbiota suggest an increase in gene abundance within pathways related to secondary metabolite production, antibiotic synthesis, and amino acid biosynthesis in the gut microbiota. To ascertain the effectiveness of the Bifidobacterium BL21 product, a consumer testing experiment was conducted by the investigators to evaluate and gather data on alterations in the gut microbiota of participants prior to and following the use of the product. The trial spanned over 8 weeks, with washout periods incorporated at the commencement and conclusion. Throughout the study, participants ingested Bifidobacterium BL21 and were subjected to a series of health examinations and assessments.

Inclusion Criteria:

1. Subjects aged 40-59 years old.
2. Normal levels of gonadotropins, testosterone, and serum prolactin.
3. No use of other traditional Chinese and Western medicines for oligoasthenoteratozoospermia treatment in the past 3 months.
4. Patients who can understand the clinical study and commit to complying with the study requirements and procedures.
5. Patients who have signed the informed consent form and are able to complete the study as per the trial protocol.

Exclusion Criteria:

1. Organic lesions of the reproductive system;
2. Use of antibiotics in the two weeks prior to recruitment;
3. Sexual dysfunctions such as erectile dysfunction, ejaculatory abnormalities, preventing completion of sexual intercourse;
4. Genitourinary infections, such as Chlamydia or Mycoplasma infections;
5. Abnormal sex hormone levels;
6. Obesity (BMI greater than 28);
7. History of allergies to the probiotic preparations used in this study;
8. Severe cardiovascular or cerebrovascular diseases, liver or kidney dysfunction, hematologic disorders, psychiatric illnesses, or other severe comorbidities;
9. Use of medications in the past 3 months that may affect the trial;
10. According to the investigator's judgment, the subject's condition does not qualify them for participation in the study.

Double(Participant,Investigator)