Isala newsflash: different factors have an impact on your vaginal microbiome  

In the past year, the Isala team has continued to work hard, so it is about time for an update! A few months after the first research phase (or our big summer campaign), the second research phase of Isala in Belgium followed. We found more and more evidence that the vaginal microbiome can be dynamic. To investigate this further, we invited 275 Belgian women to participate in this second research phase. Also in Peru, we have launched a sisterhood project with so far already more than 200 women who have donated samples. 

Today, we present the first results of the second Belgian research phase. We first examined whether the vaginal microbiome of these women had changed over several months by comparing the microbiome profile from the first phase with one from the second phase. In 7 out of 10 participants, we found the same dominant bacterium in both swabs. The dominant bacterium did change in the other participants. Interestingly, women whose vaginal profile in the first phase was dominated by lactobacilli had more often a stable microbiome. For example, women who were dominated by Lactobacillus crispatus in the first phase had a 88% chance to be so again in the second research phase. Lactobacillus crispatus is the bacterium that we already know best to be beneficial for the vaginal ecosystem. Participants who had fewer lactobacilli in the first swab and, for example, more Gardnerella, had a 62% chance of this Gardnerella dominance disappearing in the second swab.   

From these figures, we have learnt that the vaginal microbiome remains stable for the majority of participants. Yet it is certainly not set in stone. The unique composition of the microbiome and the exact ratio between the different bacteria can still vary greatly (from day to day, and probably even during the day and over longer periods of time). We only take a snapshot of the composition at that moment with the vaginal swabs. Thanks to our wonderful participants, we have already found several factors that have an impact on this. Our biostatisticians identified several of these potential factors: they compared all microbiome profiles with the answers to the 139 questions of the different surveys, with the necessary caution and the warning not to draw any hasty conclusions. Ethics remains one of Isala’s core values.  

We can say with certainty that your age plays an important role in the composition of your vaginal microbiome. This can mainly be explained by the hormone levels that fluctuate throughout every woman’s life. At Isala, we also saw a major influence of the menopause. Indeed, the vaginal microbiome menopausal Isala participants tended to be more diverse, more dominated by Prevotella and Anaerococcus and less dominated by Lactobacilli. In addition, whether or not you have children appears to have an important impact, even if you gave birth years ago. Women with children more often have higher concentrations of Bifidobacterium, Lactobacillus gasseri and Streptococcus in their vaginal microbiome, and in women without children we found more Lactobacillus crispatus

During the different phases of your menstrual cycle, your hormone levels also fluctuates, which also plays a role in the composition of the microbiome. How exactly the microbiome of one woman changes under the influence of the successive phases of her cycle, we will further investigate using the samples collected during the second Belgian phase of Isala. This will be the subject of another update later this year.  

As you are reading here that hormones influence the microbiome, it will probably not be a surprise that we also found an effect of hormonal contraception. Taking the combined pill (with estrogens) had a rather positive effect on the microbiome. We found less of the unfavourable Gardnerella and Prevotella and more Lactobacillus crispatus. In women with an IUD (with progesterone) we found more Gardnerella. Of course, this is only one aspect of the choice of a suitable contraceptive method. We keep repeating: women should always have a free choice.  

Also important to know: hormones don’t dictate everything, not even regarding your vaginal microbiome. We found that after using sanitary pads and panty liners, the microbiome is more diverse, with more Bifidobacterium, Lactobacillus gasseri, Steptococcus and Anaerococcus. When using a menstrual cup, we found more Lactobacillus crispatus and Limosilactobacillus. Based on the new results, we added the Anaerococcus and Limosilactobacillus to the eight types of bacteria, so that we now have ten types of important bacteria! You can read more details about these bacteria in their passport here and here

The participants who had sexual intercourse in the 24 hours before the swab were also more likely to have more different bacteria, including Streptococcus. We also looked at some less obvious and rather subtle connections. Different food products and drinks also seemed to be associated with the composition of your vaginal microbiome. For example, we found a negative correlation with sugary drinks and meat, which might lead to less Lactobacillus crispatus, whereas vegetables may result in a ‘healthier’ vaginal microbiome. Again, we say this with great caution, as this requires further research, as you can read in Isabelle’s earlier blog post.   

We are continuing our work, since we are absolutely sure that there are a lot more factors that determine how healthy your vagina is. Think about genetics, general immunity or a certain disease for example. But don’t forget that a vagina is self-cleaning, and thus – in principle – takes care of a healthy microbial balance itself. 

In future research phases we want to recruite as diverse and inclusive as possible across the world in different sisterhood projects. For example, people who do not identify as women but who have a vagina are very welcome to participate in our research. Inclusive work and communication is very important to us, and we hope that at Isala everyone feels welcome and recognised.   

Before the end of 2022, we will be looking for Belgian women who live under the same roof (sisters, partners, mothers and daughters, girlfriends, …) to investigate whether they have a similar vaginal microbiome. So stay tuned! For more information on the next phase of research at Isala also in other countries and even more new insights, follow us on Instagram or Twitter!