Can the health of semen microbiome impact male infertility?

Bacterial Imbalances in the Semen Microbiome Can Lead to Decreased Semen and Sperm Quality, Finds New Study. Researchers Identify Elevated Levels of Lactobacillus iners in Men with Poor Sperm Mobility.

Semen observed under a microscope

Bacterial imbalances in the semen microbiome may cause a reduction in semen and sperm quality, according to a new study.

Globally, there has been a reported decrease in male sperm count or the number of viable sperm within semen. While some research points towards pollution as a factor contributing to male infertility, it fails to explain why an estimated 30% of semen is considered abnormal.

However, a new reproductive study has shed light on a connection between the health of the semen microbiome and sperm motility. Sperm motility refers to the sperm’s ability to swim successfully through the female reproductive system and potentially fertilize an egg.

The study revealed that high levels of the bacteria Lactobacillus iners (L. iners) are associated with low sperm motility. This is the first time a distinct semen microbiome has been suggested and investigated, as well as the first time L. iners has been linked to a lowering of sperm motility. The study, published in Scientific Reports, analyzed the semen of 73 males seeking treatment for reproduction issues or vasectomies.

The Balance of Bacteria in the Semen Microbiome

Semen contains a community of bacteria in addition to “sperm helpers” like enzymes, fructose, and citric acid. Alongside L. iners, the most prominent bacteria found in semen include Enterococcus faecalis, Corynebacterium tuberculostearicum, Staphylococcus epidermidis, and Finegoldia magna.

In the study, the researchers discovered that males with abnormal semen had higher amounts of L. iners and the bacteria Pseudomonas stutzeri and Pseudomonas fluorescens. They also had lower levels of Pseudomonas putida compared to males with normal semen.

How Bacteria Affects Infertility

Dr. Vadim Osadchiy, the study’s first author and an academic urologist specializing in men’s health and infertility, explained the potential impact of L. iners bacteria on infertility. In females, L. iners can act as a symbiotic organism, maintaining a healthy vaginal microbiome and preventing the growth of harmful bacteria. However, some studies suggest that it may predispose a person to bacterial vaginosis or sexually transmitted infections.

Dr. Osadchiy also noted that the abundance of L. iners in the vaginal microbiome may affect success rates in fertility treatments. However, the impact of L. iners on male factor fertility and men’s health remains largely unexplored.

The relationship between the semen microbiome and the gut microbiome remains unclear. While the urinary and semen microbiomes are interconnected, the relationship becomes more tenuous the farther they are from the reproductive tract. There is currently no definitive data on how a gut microbiome with inflammation may affect the semen microbiome.

Dr. Menka Gupta, a functional medicine doctor, suggests that improving semen microbiome health could be achieved by prioritizing gut health. Factors such as diet, stress levels, and toxin exposure may influence the connection between the gut and the semen microbiome. However, further research is needed to establish a clearer understanding of this relationship.

###a Improved Fertility Through Healthy Lifestyle Choices

While the exact relationship between the semen microbiome and fertility outcomes requires more exploration, adopting healthy lifestyle choices can have a positive impact on sperm quality and motility. These choices include regular exercise (both cardio and strength training), practicing mindfulness and meditation to reduce stress, avoiding processed foods, and increasing fiber intake.

Dr. Gupta also highlights the importance of abstaining from alcohol and smoking, as well as following a diet rich in antioxidants and probiotic foods. By prioritizing these lifestyle choices, individuals may improve their overall health, including the health of the semen microbiome.

It is worth mentioning that this study represents just one piece of the puzzle, and there is still much to learn about the body’s microbiomes in general, including the semen microbiome. As Dr. Osadchiy emphasizes, understanding microbial community interactions is essential for contextualizing findings. Additionally, further exploratory work with larger sample sizes and greater geographic diversity will aid in better characterizing the variability of the semen microbiome.

Q&A: Addressing Additional Concerns

Q: Can bacterial imbalances in the semen microbiome be treated? A: While more research is needed, some experts believe that focusing on improving overall gut health may positively impact the semen microbiome. Prioritizing a healthy lifestyle, including a balanced diet, regular exercise, and stress reduction, may contribute to a healthier microbiome.

Q: Does a healthy semen microbiome guarantee fertility? A: The relationship between the semen microbiome and fertility outcomes is still being explored. A healthy semen microbiome is just one factor that can contribute to fertility, so it is not a guarantee. Other factors, such as sperm quality and the overall reproductive health of both partners, also play crucial roles.

Q: Are there any specific probiotic strains that can improve the semen microbiome? A: The use of probiotics to target the semen microbiome is still an area of ongoing research. At present, there is no specific probiotic strain that has been proven effective in improving the semen microbiome. However, maintaining a diverse and balanced gut microbiome through a healthy diet and lifestyle may indirectly support the health of the semen microbiome.


  1. [Scientific Reports: Semen Mi