The Curious Phenomenon of “Keto Crotch”

March 12, 2019

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I have a confession to make: I, Mark Sisson, suffer from keto crotch.

It’s embarrassing, really. I thought maybe it was just the change in climate moving from Malibu to Miami—the humidity, the heat, the fact that I’m paddling and swimming more often now. There’s a whole lot of moisture down there. Perpetual steaminess.

But then I met up with my writing partner and good pal Brad Kearns, who’s been working with me on my upcoming book. Brad lives in Northern California, which is far from hot or humid right now. He’s also a staunch keto guy most of the time, and, well, let’s just say I could smell him before I could see him. We met up at a coffee shop and cleared out everyone in a fifteen foot radius. We sampled a new exogenous ketone product he’s been trying and not one, not two, but three separate individuals approached to inquire if we were salmon fishermen.

Okay, let’s get serious. Does “keto crotch” really exist? And, if it does, what can you do to prevent it?

I’m writing this not because of overwhelming demand from loyal followers of the Keto Reset plan. In fact, I hadn’t ever heard of “keto crotch” before last week. There’s a good chance almost no one heard of it before March 2019, if Google Trend data for “keto crotch” searches is any indication. I’m writing this post because the barrage of news articles, Twitter hashtag campaigns, and extremely serious warnings from people with lots of acronyms after their name has led people to ask me if it’s a legitimate phenomenon. A few acquaintances have brought it up in social situations. Our marketing director found herself fielding keto crotch questions at a dinner for Expo West last week.

So, are women following a ketogenic diet experiencing an epidemic of stinky vaginas?

Probably not.

Is Keto Crotch Even Physiologically Plausible?

Vaginal odor does change. It fluctuates naturally, and sometimes it can get worse. The most common cause of unpleasant changes to vaginal odor is bacterial vaginosis, which occurs when something upsets the balance between the beneficial lactobacilli bacteria that normally live in the vagina and pathogenic bacteria. What can upset the balance?

The vagina is supposed to be an acidic environment; that’s how the healthy lactobacilli thrive. If something upsets that pH balance, tilting it toward alkalinity, unhealthy bacteria gain a foothold and become predominant, and begin producing unpleasant-smelling amines like putrescine, tyramine, and cadaverine. This is bacterial vaginosis. As it turns out, the lactobacilli bacteria normally present in the vagina are instrumental in maintaining an acidic pH. They consume glycogen, spit out lactic acid, and exert antimicrobial and antifungal effects that block common vaginal pathogens like candida, e. coli, and gardnerella from taking hold and causing trouble.

The interaction between diet and vaginal biome is understudied. To my knowledge, there exist no direct controlled trials that address the issue. It’d be great to have a study take a cohort of women, split them up into different dietary groups, and follow them for a year, tracking their vaginal pH and bacterial levels. Alas, we do not.

We do have a study that provides a hint. In 2011, researchers looked for correlations between dietary patterns and bacterial vaginosis in a cohort of nearly 2000 non-pregnant mostly African-American women aged 15-44. While there probably weren’t many keto dieters, and the diets as a whole were of the standard American variety, glycemic load—which basically boils down to carb load—was the strongest predictor of bacterial vaginosis. Other markers of food quality, like a person’s adherence to “healthy eating guidelines,” initially seemed to reduce the chance of bacterial vaginosis, but those relationships were almost abolished after controlling for other factors. Only glycemic load remained highly significant.

This connection between dietary glycemic load and bacterial vaginosis starts looking more causal when you realize that diabetes—a disease where one’s “glycemic load” is perpetually elevated and exaggerated—is another risk factor for bacterial vaginosis.

There’s also a 2007 study that found “high” intakes of dietary fat, particularly saturated and monounsaturated fat, were a significant predictor of bacterial vaginosis. In this study, “high fat” meant around 39% of energy from fat. That leaves 61% of energy from carbohydrate and protein, the kind of “high-fat, high-carb” Standard American No-Man’s-Land that’s landed the country in the current metabolic predicament. High-fat intakes in the presence of high-carb intakes may very well be bad for your vagina, but it says nothing about the likelihood of keto crotch.

At any rate, neither study was a controlled trial, so we can’t say anything about causality.

What about a yeast infection? The most common offender is candida, which usually favors sugar for fuel, but there’s also evidence that it can metabolize ketones. Could keto make a latent yeast infection worse and lead to smelly “keto crotch”?

Perhaps keto can make candida worse (that’s for another day), but that’s not the cause of “keto crotch.” Candida vagina infections don’t smell very much, if at all, and they certainly don’t smell “fishy.” That’s only caused by bacteria and the aforementioned amines they can produce.

Free glycogen levels in vaginal fluid are a strong predictor of bacterial vaginosis. If ample glycogen is available, the good lactic acid bacteria have plenty of food and produce plenty of lactic acid to maintain the acidic pH conducive to vaginal health. If inadequate glycogen is present, the lactic acid bacteria have less food and produce less lactic acid, increasing the chances of the pH tilting toward alkalinity. An alkaline vagina is a vagina where pathogenic bacteria—the ones that produce stinky amines—can establish themselves.

The question then is if ketogenic diets lower free glycogen in the vaginal fluid. That’s a fair question. I wasn’t able to find any solid answers. I guess “ketosis effect on vaginal glycogen” isn’t the most lucrative avenue of scientific inquiry.

Should I Worry?

Even assuming this is a real phenomenon, it’s a rare one. The vast, vast majority of people following a ketogenic diet aren’t coming down with keto crotch. Other than a few Reddit posts from the past 5 years, I haven’t seen anyone at all in our neck of the woods complain.

Maybe people doing Primal keto are eating more nutrient-dense ketogenic diets than people doing conventional (or caricature) keto. Salads, steaks, eggs, and lots of non-starchy veggies are a great way to stay keto and obtain micronutrients. And there are links between micronutrient status and bacterial vaginosis. The most common relevant deficiencies include vitamin D (correcting the deficiency can cure the vaginosis) and folate. Hard to get adequate folate if your diet is based on salami and cream cheese.

We also know that the health of your skin biome tracks closely with that of your gut, and that eating plenty of non-starchy veggies, fermented foods (yogurt, kefir, sauerkraut, kimchi, etc), and colorful produce can provide prebiotic fiber, prebiotic polyphenols, and probiotic bacteria that nourish your gut biome. If the vaginal biome is also connected to the gut biome (and it is), tending to the latter should also have positive effects on the former.

The Primal brand of keto tends to emphasize micronutrients and gut health a bit more than some other types of keto I see floating around. If—and it’s a very big “if”—keto crotch is legit, that may explain some of the discrepancy.

Finally, be sure to check out this very interesting Twitter thread where the author lays out his suspicions that the whole “keto crotch” phenomenon might be a manufactured stunt designed to vilify the ascendant ketogenic diet. Nothing definitive, but it’s certainly food for thought.

If You’re Concerned…

Okay. Say you’ve recently gone keto and your vagina is smellier than usual. (And you’ve ruled out other, more obvious potential causes like changes in soaps, etc.) It’s hard to ignore, and I wouldn’t want you to. What can you do?

Confirm that you have bacterial vaginosis. Seriously, get it checked out.
Make sure you’re getting enough folate and vitamin D. Supplement if need be.
Eat prebiotics and probiotics. Fermented food and/or a good probiotic supplement.
Try a carb refeed. If ketosis depletes vaginal glycogen and increases pH, the occasional carb refeed could restore glycogen by 30-50 grams and should do the trick. Note that this is entirely theoretical; I’m not saying it’s a “problem” on keto.
Hang out in the keto zone. I’ve written about the keto zone—that metabolic state where you’ve reached full keto and fat-adaptation and find yourself shifting in and out of ketosis as you please due to increased metabolic flexibility. A few carbs here, a fasting day there, a few more days of keto. Again, if full keto is theoretically depleting vaginal glycogen, maybe relaxing your restrictions will solve the issue while maintaining your fat adaptation. This is actually where I hang out most of the time.

That’s it for today, folks. Do you have “keto crotch”? Do you know anyone who does? Or did your vaginal health improve on keto? I’m curious to hear what everyone’s experiences have been, so don’t be shy.

Take care and be well.