Do You Know The State Of Your Vagina's Microbiome? Here's Why It Matters

When things are going well in the vagina, millions of good bacteria (certain species of Lactobacillus) happily reside on the vaginal walls and within vaginal fluid. There they metabolize the sugar molecule glycogen inside the vaginal tissues, producing lactic acid as a result.

In a happy vagina, the lactic acid from Lactobacillus creates a pH between 3.5 and 4.5. This means vaginal fluid should taste slightly tangy but not sour: Think yogurt or merlot, not lemon juice.

Even though people are highly diverse in age, race/ethnicity, and sexual behavior, their vaginal microbiomes can typically be classified into one of five major categories, called vaginal community states 1 through 5.

These include optimal and less optimal environments for sexual and reproductive health. In the optimal community states (I, II, III, and V), Lactobacillus dominates, the pH is nicely acidic, and all is right with the world.

Community states on the other end of the spectrum are different. In community state IV, Lactobacillus may be present, but they are less plentiful, allowing the growth of diverse groups of bacteria who also thrive in the vagina's anaerobic environment. Gardnerella vaginalis is the best known among these, but there are dozens of others with names reminiscent of Cinderella's stepsisters: Prevotella, Sneathia, Eggerthella.

Pictured above: Species of bacteria in the vaginal fluid of 220 women. Each woman is represented by a thin horizontal line, and more shades of gray represent a greater diversity of bacterial species.

Women with BV (microbiome often in community state IV) have more diverse bacteria compared to women without BV (microbiome often in community states I, II, III, and V).

However, less optimal states aren’t always associated with disease.

Researcher Jacques Ravel, Ph.D., found these community states in over a third of healthy Black and Hispanic women and almost 20% of Asian women, compared to less than 10% of white women. Notably, his team didn't actually ask women about symptoms, and they couldn't tell whether the differences in community state were related to genetics, personal habits, or sexual practices. While Lactobacillus-poor community states may be "normal" for some women, these women are more vulnerable to developing discharge and odor, plus other negative outcomes related to pregnancy and acquisition of STIs/HIV. 

Just like in any neighborhood, the vaginal bacterial community state can shift and change. Some vaginas stay in one state for weeks, while others can change dramatically over the course of a day. The monthly presence of menstrual blood (pH 7.4) causes everyone's vaginal microbiome to take a hit. Lactobacillus concentrations go down, and Gardnerella concentrations go up. Vaginal pH also takes a hit when semen enters the picture (pH 7.2–7.8).

We all know people who are as stable as rocks: They lose their jobs, break up with their partners, and crash their cars, yet they remain steady and calm. (I am not one of these people, but I know they exist.) On the other hand, there are people who are barely holding it together, where you know any tiny stressor might just push them over the edge.

Vaginas are like this too. A resilient vagina can take multiple insults, and its microbiome quickly recovers to its usual state. However, for a fragile vagina, even a small insult like semen or menstrual blood can push it into a state of chaos. (Note that vaginal resilience does not appear to be related to emotional stability. You can be a hot mess and have a vagina of steel.)

Many forces can affect the resilience of the vagina, and one of the most powerful of these is estrogen. Lactobacillus thrive when estrogen is most plentiful, typically during the decades after puberty and before menopause. When perimenopause strikes, the roller coaster of waxing and waning estrogen levels doesn't just cause hot flashes and changes in bleeding. This hormonal instability can result in declines in Lactobacillus, placing a previously stable vagina in a more vulnerable state.

This isn't just a women's issue. When transgender men begin testosterone therapy, estrogen levels in the vagina plummet, and the vaginal microbiome transitions toward a menopausal state. So just when transgender men might be enjoying the masculinizing effects of testosterone, they may face more vaginal troubles than they did before they began their hormonal transition.

While the effects of menstruation, menopause, and hormones on the vagina are often outside of our control, we do have power over what we choose to put inside them. The only things that have any business inside the vagina are for pleasure or menstruation: fingers, sex toys, tampons/menstrual cups, or penises (one at a time is easiest).

Here's a good rule of thumb: If you wouldn't put it in your mouth, then don't put it in your vagina. (OK, no one actually puts clean tampons in their mouth, but you could.) Unfortunately, the converse isn't true. Keep that pizza out of your vagina, as it will wreak havoc on your microbiome.