Male Infertility: It takes two!

Written by Clare Carrick ANutr BHSc (Nutrition and Health Promotion)

Scientifically reviewed by Dr Fathalla Ali, PHD Paediatrics


“Just relax and it’ll happen for you Sarah” says Auntie Joan…”You’re probably just working too hard to fall pregnant.”

This exchange is all too common. No consideration for the man and his role in fertility…No acknowledgement that HE could be the one whose work or lifestyle is impacting the chance of conception!

Infertility is one area of health that has all too often been blamed on women. Given that male factors are estimated to be responsible for around 40-50% of infertility cases, there is a clear case for sharing this heavy load, and the need for an increased awareness of the potential factors influencing male fertility (1).


Male Infertility Causes

A lot of the time, the reason for male infertility remains a mystery (1). In about 15% of infertility cases, some kind of infection is thought to be responsible (1). Many infections of the sperm go undetected, and can cause damage to the sperm concentration, potentially contributing to infertility (2). More recently, the importance of the human microbiome and its influence on fertility has come under the spotlight (1, 3).


Fertility and the Microbiome

We now know that our various microbiomes play a key role in human health (1). Our gut, mouth, vagina, skin, and semen all play host to their very own special community of microbes, and the way these microbes interact with various parts of our bodies can change our health and influence our disease status (1). With this in mind, it shouldn’t really come as a surprise that the microbiome of semen seems to have some sway on whether or not the host (i.e. the guy) is able to impregnate someone, however, whilst there has been quite a lot of research into the female genital microbiome and fertility, males have been a bit neglected, until quite recently (1, 3). 


Semen Bugs

Scientists have found that the differing bacterial communities in semen are associated with semen quality. These semen communities are categorised depending on which bacterial strain is dominant, for example, mostly Lactobacillus, or mostly Prevotella (1). Lactobacillus-dominant semen is associated with higher quality semen, whereas semen that is Prevotella-dominant is around 8.5 times more likely to contain more than two clinical abnormalities…i.e. Prevotella-dominant semen is lower quality (1).  


It’s All About the Balance

It’s not quite as easy as simply exterminating the ‘bad bacteria’ to boost fertility. In fact, most healthy semen contains some of the bacteria that are seen as ‘less beneficial’ without any issues…(1). Interestingly, though, the presence of bacteria that are seen as being ‘more beneficial’ (like Lactobacillus) may not only help maintain semen quality, but also shield against the negative effects of bacteria like Prevotella (1). 


Probiotics for Sperm Health?

Several studies have looked at using probiotics, or other microbiome-altering methods, to address any imbalances and restore the more ‘beneficial’ bacteria back to the semen microbiome (3). One study found that supplementing with Lactobacillus and Bifidobacterium for just 6 weeks improved sperm motility and reduced the number of DNA breakages (4). Another study found that daily supplementation with Lactobacillus paracasei, arabinogalactan, fructo-oligosaccharides, and l-glutamine for 6 months improved sperm count and motility and reduced the number of atypical forms in the sperm (5). 


Future Directions

With all of this exciting research comes the potential to approach infertility from a new angle. Microbiome-targeted therapies offer something different for couples struggling to conceive, but there are still some gaps in the research. What is made clear, on all accounts, is that it really does take ‘two to tango’!




  1. Weng, S. L., Chiu, C. M., Lin, F. M., Huang, W. C., Liang, C., Yang, T., Yang, T. L., Liu, C. Y., Wu, W. Y., Chang, Y. A., Chang, T. H., & Huang, H. D. (2014). Bacterial communities in semen from men of infertile couples: metagenomic sequencing reveals relationships of seminal microbiota to semen quality. PloS one9(10), e110152. 
  2. Boeri L, Pederzoli F, Capogrosso P, Abbate C, Alfano M, Mancini N, Clementi M, Montanari E, Montorsi F, Salonia A. Semen infections in men with primary infertility in the real-life setting. Fertility and Sterility. 2020 Jun 1;113(6):1174-82.
  3. Tomaiuolo R, Veneruso I, Cariati F, DArgenio V. Microbiota and Human reproduction: The case of male infertility. High-throughput. 2020 Jun;9(2):10. 
  4. Valcarce DG, Genovés S, Riesco MF, Martorell P, Herráez MP, Ramón D, Robles V. Probiotic administration improves sperm quality in asthenozoospermic human donors. Beneficial Microbes. 2017 Apr 26;8(2):193-206.
  5. Maretti C, Cavallini G. The association of a probiotic with a prebiotic (Flortec, Bracco) to improve the quality/quantity of spermatozoa in infertile patients with idiopathic oligoasthenoteratospermia: a pilot study. Andrology. 2017 May;5(3):439-44.

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