A Field Guide to Your Vaginal Microbiome

The microbes that naturally flourish in our nether regions are team players: They support a delicate equilibrium and help to keep our reproductive organs healthy. Though scientists have known for over a century that the vagina’s microbiology is complex, they are just starting to crack the microscopic code of what keeps it balanced and what throws it out of whack. Just like with gut bacteria—which have been linked to a plethora of issues including weight gain and mood disorders—the vagina’s particular microbial mix is now thought to play a role in mediating the risk of certain cancers, protecting against STIs and vaginal infections and, potentially, bringing pregnancies to term.

(Related: Are Your Bath Products Bad for Your Vag?)

Like plenty of things bits-related, the vaginal microbiome gets swinging during puberty. (The microbes are thought to proliferate as estrogen shoots up, though more research is needed to confirm this link.) That’s when lactobacilli, a type of bacteria that produces lactic acid, start getting cozy in the female sex organs. The Lactobacillus crispatus variety (which experts call L. crisp, aka the Queen Bee of vag bacteria) helps create an ideal vaginal pH below 4.5.

(Researchers think these lactobacilli may originate in the gut and find their way to the vagina because of its proximity to the anus—a totally normal biological phenomenon, and nothing to worry about.) An acidic environment is necessary for vaginas to keep them better protected from invading bacteria and fungi. In many women, L. crisp will make up 95 percent of the vaginal microbiome. Unlike in the gut, which is home to a thick layer of mucus, bacteria in the vaginal canal live directly on its internal epithelial tissue.

Hints about the vagina’s microbiological complexity first showed up under microscopes in the early 1900s, when scientists were baffled by the rod-shaped lactobacilli and deposits of glycogen (a form of glucose) they were seeing in these tissues. Glycogen plays a role in the body’s energy storage and is usually found in the liver, so scientists were surprised to find it in the vagina, explains Laura Sycuro, an assistant professor at the University of Calgary’s Cumming School of Medicine who runs a research group that investigates the vaginal microbiome. More than a century later, researchers are still working to prove their hypothesis (and, due to chronic underfunding, it continues to be a hypothesis) that glycogen feeds the lactobacilli. What researchers like Sycuro are starting to understand is that this living environment is constantly in flux, as it’s altered by things like menstrual flow, pregnancy, menopause or the exchange of bodily fluids.

Why the microbiome matters

Thanks to millennia of medical literature dominated by male voices, there’s a fundamental and pernicious misunderstanding of how female bodies work. For example, drawing on Ancient Greek ideas, physician and chemist Edward Jorden claimed in a 1603 text that uteruses were prone to…wandering. Then there was the 19th-century belief that women shouldn’t board trains because travelling at more than 50 miles per hour could make our uteruses shoot out of our bodies (yes, really). We may now have at least basic female anatomy figured out, but women’s health continues to be underexamined, and the vaginal microbiome in particular remains—unnecessarily—an enigma. Researchers still have to fight for funding and are often faced with surprising ignorance when it comes to female biology. “Reviewers fundamentally did not believe me that bacterial vaginosis, or BV, is caused by bacteria, and I’m like, okay, so this is 30 years of clinical research,” says Sycuro. (The review panel insisted that fungi are also a major player in vaginosis, but Sycuro says that’s complete nonsense.)

Every year, bacterial vaginosis—an infection that’s intimately linked to the vaginal microbiome—affects about 30 percent of vagina-havers worldwide and costs health-care systems billions of dollars in doctor visits and treatment. BV is more common than yeast infections—it’s responsible for 40 to 50 percent of diagnosed vaginitis infections—and it’s tied to both preterm births and HIV infection. (Studies show that BV increases the risk of HIV infection in women by 60 percent.) BV—which has symptoms such as thin discharge and the occasional fishy smell—is often trivialized by the scientific community, says Sycuro, because it’s not fatal. But it’s still a hugely disruptive hassle that causes discomfort and, unfortunately, the unwarranted shame that many women feel or associate with their genitalia.

BV isn’t the only culprit causing issues under our undies, of course. Yeast infections are to blame for another 20 to 25 percent of vaginitis cases—but they aren’t bacterial, they’re fungal. These infections are caused by yeast overgrowth, and are accompanied by thicker discharge and the occasional itching or burning sensation.

And as for those dreaded burn-when-you-pee urinary tract infections, rather than an internal imbalance, they can be caused by a pathogen from the GI tract—like E. coli—getting into the urethra and bladder.

Unlike yeast infections, for which you can get over-the-counter anti-fungal creams, treatments for BV are limited—a prescription for antibiotics is the only option, and it comes with its own slew of potential issues. “Once [patients] are in that loop, every time they take antibiotics, they have a 50 percent chance of needing the antibiotics again within six to 12 months,” says Sycuro. Antibiotic over-prescription can also increase a person’s anti-microbial resistance and alter their gut microbiome diversity. Translation? These medications clear out the bad guys, but they don’t necessarily restore perfect balance, and sometimes the bad guys return. Patients end up back at square one, taking more pills that further disrupt the vaginal microbiome.

The cancer connection

Research is underway to examine the vaginal microbiome’s role in protecting against sexually transmitted infections like chlamydia, gonorrhea and HIV: Sycuro’s lab is currently studying whether chlamydia bacteria can attach better to a receptor when certain other bacteria are present. This is especially important because some research findings suggest that chlamydia is associated with a higher risk of ovarian cancer.

Compared to, say, prostate cancer, says Sycuro, female-specific diseases such as ovarian, uterine and cervical cancers are understudied, and harder to detect at early stages. While prostate cancer can be detected early through blood tests, women don’t have that luxury when it comes to ovarian and uterine cancer: An estimated 1,950 of the 3,000 Canadian women diagnosed with ovarian cancer in 2022 were predicted to die, according to the Canadian Cancer Society, mostly due to it being caught too late. (Pap tests only help detect cervical cancer.)

What’s next on the horizon

When it comes to long-term solutions to chronic BV, Sycuro says there is a glimmer of hope. Inspired by fecal transplants used to improve digestive health, scientists are experimenting with transplanting fluid from healthy vaginas into ones with chronic BV. This procedure is still in the clinical trial phase, with research underway in places like the Kwon Lab in Cambridge, Massachusetts, and Sycuro estimates it might take another decade for the process to become widely accessible. In the meantime, we need to dodge the savvy marketing behind iffy products that try to fill that medical void and claim to support “vaginal wellness.”

Next: What’s With All the Vaginal Creams, Wipes and Gummies?