It was a fascinating read in February on Motherboard: Cecile Westbrook, a PhD student from Madison, Wisconsin, attempted to make yogurt from her own vaginal bacteria.

A gross idea, that nevertheless fits in well with modern microbiology. Most important discoveries in recent years had pretty disgusting aspects to them. You may have heard of those intestinal C. diff infections for example, that are no longer treated with antibiotics, but with faecal transplants. Then there are the microbiome studies that show how vaginal and faecal bacteria end up in babies during the birthing process, resulting in microbial differences between C-section babies and vaginally delivered ones. A somewhat modern father (like microbiologist Rob Knight) does not hesitate to rub a new-born baby with its mother’s vaginal fluid after a C-section. Microbiology is no longer just about fighting the bad bugs by smothering them in an ocean of antibiotics. All over the world people are fascinated by the positive influence bacteria can have on their health.

Enter Cecile Westbrook. While talking to a friend she wonders what probiotic treasures could be lurking in her own vagina. The conversation is giggly at first, with many obvious jokes about the beneficial effects of oral sex and the names to invent for a probiotic yogurt cultured with “jazz juice”. But Westbrook takes it seriously. A quick search on the Internet revealed little on the subject, whereas there is a whole cookbook available on how to make the most of a man’s juices. She decided to try it herself, grabbed a wooden spoon, stuck it in her vagina and stirred it into a bowl of milk.

The result? An extremely sour but apparently yogurt-like substance. “She compared it to Indian yogurt and ate it with blueberries.”

Is Cecile Westbrook crazy? Probably. But the connection she saw between vaginal bacteria and yogurt is a sound one. Lactobacillus is the name of the bug. Yogurt-Lactobacillus is not all that different from the vaginal lactobacilli that I now study as a postdoc in the lab of Dr. Amanda Lewis at Washington University, St Louis. They all produce heaps of lactic acid, both in the vagina and in yogurt. In contrast to most other bacteria, they thrive in the acidic environment that they create themselves. “Acidophilus” is the name of the group to which they belong. Latin for “acid lovers”.

Westbrook claims in an interview with the feminist blog Jezebel that we know very little about vaginal flora, but that’s nonsense. Through the efforts of the human microbiome project, the genetic information of more than 400 vaginal bacteria has been mapped. The results are fascinating. In microbial terms, the vagina appears to be very different from the rest of the body. Of all the body sites the vaginal microbiota shows the least diversity, both within and between women. Lactobacillus dominates most vaginas. And not just one Lactobacillus, but one or two of only four kinds, which are also all closely related: crispatus, jensenii, gasseri and iners. These specific types of bacteria feel very at home in the vagina. Or at least, in the human vagina. In some of our closest relatives, chimpanzees, baboons and mangabeys, lactobacilli are hardly found. No other species have been discovered with an acidic vagina. It is a rather human phenomenon.

Another remarkable characteristic that sets the vagina’s microbiota apart is the correlation between bacteria and health. In other body sites, especially the intestine, a lower diversity of bacteria goes hand in hand with bad health.  Obesity and Crohn’s are the best known examples of this. But in the vagina this relationship is reversed: the fewer species, the better. In the minority of women who do not carry lactobacilli, an enormous diversity of other kinds are found, such as Gardnerella, Prevotella and Atopobium. This is called bacterial vaginosis. Around 20% of white women in the USA have this type of flora. The numbers of Hispanic and black women are higher, for unknown reasons. Women who have this type flora, which we call “Bacterial Vaginosis”, regularly suffer from foul fishy odor and thin secretions. And those are just the uncomfortable but harmless consequences. Women lacking Lactobacillus have a greater chance of infection with gonorrea, Chlamydia, and HIV when they have sex with an infected man. There is a correlation between absence of Lactobacillus and urinary tract infection. Pregnant women without lactobacilli have a greater chance of premature birth and higher chances of carrying group B streptococci. This type of bacteria can be transferred during birth and is the leading cause of neonatal meningitis in the U.S.

In short, one hopes that Westbrook did not have vaginosis when she sampled herself; and not just for her own health. Even if it were possible to make yogurt with Gardnerella or Prevotella, the resulting product would, in all likelihood, smell like rotten fish.

What Westbrook’s yogurt smelled like was not mentioned in the story. But it seems that her bacteria, after a night in the milk, actually did deliver a product similar to yogurt. Is that really possible then? Can the vaginal lactobacilli really acidify and curdle milk as well as their yogurt cousins?

We cannot conclude much from the experiment she carried out. The idea was nice, the execution poor. The wooden spoon is especially concerning. Wood has its own flora. In a wooden vat you can make wine from grape juice using all sorts of wild, untamed microorganisms living in the vat. That’s all very hipster and microbrewery-like, but you have no idea what actually did the trick. It’s entirely possible that a germ from the spoon offered a helping hand to make Ms. Westbrook’s yogurt. After all, in order to ferment yogurt you need more than just a Lactobacillus. In nearly all yogurt cultures there are two species : a Streptococcus thermophilus (in full: Streptococcus salivarius subsp. thermophilus) and a Lactobacillus bulgaricus (in full: Lactobacillus delbrueckii subsp. bulgaricus). Every yogurt you buy in the supermarket is the result of a wonderful duet between the two. On its own Lactobacillus barely gets out of the starting gates in milk, but with Streptococcus by its side it does the job without a hitch. Its fermentation partner is thought to provide the necessary nutrients, such as formic acid, folic acid and fatty acids. The same is true of Streptococcus. In milk it barely gets going by itself. It needs Lactobacillus to chew up the milk proteins. Together they form a golden duo, which turns billions of litres of milk a year into smooth, creamy yogurt.

It therefore seems unlikely to me that the vaginal lactobacilli fermented the milk by themselves. To be sure, I carried out a little test. Not with my own bacteria of course – that’s private – but with a number of different lactobacilli from a cohort of healthy pregnant women whose bacterial isolates we study in the lab. The test showed that the vaginal lactobacilli are useless when it comes to fermenting milk. I tested two strains of each of the four most common types (crispatus, iners, gasseri and jensenii). From a total of eight bacteria, only one was remotely successful in acidifying the milk. In this case, the result was particularly chunky; sour milk, probably with loads of precipitated milk protein. In any case, it was no delicious tangy yogurt.

The conclusion is that the yogurt from Ms. Westbrook probably contained a mixture of various kinds of bacteria. Some of which may have been her own vaginal inhabitants, but a number of them may have originated from the wooden spoon, or from the air, or from the kitchen counter, or from underneath her fingernails.

It’s still an interesting idea though. The story is not as disgusting as it appears. A bacterium is a living organism; it reproduces itself. You can simply take it from the vagina and allow it to divide dozens of times. After several generations, not  a single molecule of vagina would remain.

These bacteria can easily be tested to assure they won’t make you sick. And then you can do whatever you want with them. Try making yogurt; you might well succeed as long as you include a Streptococcus. You could even add it to a normal yogurt and create your own individualized power breakfast.

But there are more applications than just yogurt. In the future a woman may keep a few ampules of her own bacteria in a freezer as a backup.  She could apply them whenever her flora needs some support, for example after sexual encounters, illness, antibiotics, or maybe even to rub on her baby if it is born by caesarean section.

Cecile Westbrook may have gone about her work somewhat clumsily, but her story fits very well in the important trend from anti- to probiotics. And as for the unappetizing aspect? I guess we should just get over it.