Keto and the Menstrual Cycle: Is There Reason To Worry?

It seems every “keto for women” forum abounds with stories about menstrual cycles gone wild in the first few months of keto. Irregular cycles, breakthrough bleeding, and periods lasting much longer than normal are common complaints. Sometimes these stories are cited as evidence that keto isn’t good for women, at least not premenopausal women, and that we need carbs for healthy hormones. Yet, many women don’t notice any changes in their menstrual cycles at all, while others report improvement in PMS symptoms and cycle regularity from the get-go.

What gives? Why do some women’s cycles apparently become wacky when they start keto, while others feel like keto is the key to period bliss? Can keto “mess up” the menstrual cycle?

We know that diet—what and how much we eat—can profoundly affect our hormones. This is true for both women and men. One of the reasons people are so excited about ketogenic diets is specifically because keto shows promise for helping to regulate hormones and improve cellular sensitivity to hormones such as insulin and leptin.

At the same time, women’s hormones are especially sensitive not only to dietary changes but also to downstream effects such as body fat loss. Furthermore, one of the ways women’s bodies respond to stressors is by turning down the dial on our reproductive systems. It’s reasonable to hypothesize, then, that women might have a tougher time adapting to or sustaining a ketogenic diet. Keto can be stressful depending on one’s approach, and that might negatively impact women’s reproductive health. But do the data actually bear that out, or is so-called “keto period” more misplaced hype than genuine fact?

Note that throughout this post, I’m going to use the term “reproductive health” to refer to all aspects of women’s menstrual cycle, reproductive hormones, and fertility. Even if you aren’t interested in reproducing right now, your body’s willingness to reproduce is an important indicator of overall health. When your reproductive health goes awry—irregular or absent periods (amenorrhea) or hormone imbalances—that’s a big red flag. Of course, post-menopausal women can also experience hormone imbalances that affect their health and quality of life (and low-carb and keto diets can be a great option for them).

Menstrual Cycle 101

Let’s briefly review what constitutes a normal, healthy menstrual cycle, understanding that everybody’s “normal” will be a little different. A typical cycle lasts from 21 to 24 days on the short end to 31 to 35 days on the long end, with 28 days being the median. Day 1 is the first day of your period and begins the follicular phase, which lasts until ovulation. Just before ovulation, levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), and estradiol (a form of estrogen) spike. Next comes the luteal phase covering the approximately 14 days from ovulation to menses. LH, FSH, and estradiol drop, while progesterone rises. Estradiol bumps up again in the middle of the luteal phase. If a fertilized egg is not implanted, menstruation commences, and the whole cycles starts over again. All this is regulated by a complex communication network under the hypothalamic–pituitary–gonadal (HPG) axis, which is closely tied to the actions of the adrenal (the A in HPA axis) and thyroid glands.

Across the cycle, fluctuations in body weight are common as fluid is retained and then released along with shifts in estrogen and progesterone. Changes in blood glucose are also normal, and insulin-dependent diabetics often find that they need to adjust their dose at different times of their cycles to keep their blood sugar in check. The most common pattern is higher blood glucose readings in the pre-menstrual period (the second half of the luteal phase), and lower readings after starting your period and before ovulation. This is generally attributed to the fact that progesterone, which is highest during the luteal phase, is known to reduce insulin sensitivity. However, different women experience different patterns, which can also be affected by other factors such as oral contraceptive use.

Normal fluctuations in insulin resistance and blood glucose can mean that women get lower ketone readings at certain times of the month than others. When these occur premenstrually—and so they tend to coincide with a period of (transient) weight gain and food/carbohydrate cravings—women often feel as though they are doing something wrong. Rest assured that these variations reflect normal physiology.

The many factors that affect your cycle and the levels of your sex hormones include: other hormones, gut health and microbiome, metabolic health (e.g., insulin sensitivity), environmental toxins, stress, sleep, immune health, nutrient deficiencies, activity level and energy expenditure, and age. Each affects the others, and all (except age of course) can be affected by diet. It’s no surprise, then, that it can be extremely difficult to pin down a root cause of menstrual changes or reproductive issues.

What the Research Tells Us About Keto and Menstruation

As I said at the outset, there are lots of anecdotes, both positive and negative. In my experience, most women whose cycles seem to go crazy when they start keto find that things get back to normal—and often a better version of normal—after a few months.

First, it’s tricky to determine the effects of keto per se, since many people combine a ketogenic diet with calorie restriction (intentionally to lose weight or unintentionally due to the appetite suppressing effects of keto) and with fasting (intermittent and/or extended). Each of these can independently impact the factors listed above, lead to weight loss, and affect the menstrual cycle and reproductive health.

So, is there any evidence that keto itself causes changes to menstruation?

The scientific evidence is scant….

The one statistic you’ll see floating around the interwebs is “45% of (adolescent) females experience irregular menstrual cycles on keto.” This statistic comes from one small study of adolescent girls using a therapeutic ketogenic diet to treat epilepsy. Six of the twenty girls reported amenorrhea (loss of period) and three were diagnosed with delayed puberty. However, the ketogenic diet used for epilepsy is different and usually much stricter than an “everyday” keto diet needs to be, and epilepsy is frequently associated with menstrual dysfunction regardless of diet.

To extrapolate the findings of this study and argue that nearly half of teenage girls (or women generally) are likely to experience menstrual problems from going keto is a huge leap.

The fact is, I’m unable to find any studies done in healthy human females (or mice for that matter) demonstrating that otherwise normal menstrual cycles are disturbed by going keto.

5 Ways Keto-Related Factors *Might* Affect Your Menstrual Cycle

With the limited amount of research looking directly at keto and menstruation, let’s look first at whether there are direct effects of carbohydrate restriction or elevated ketone production on the menstrual cycle. Those are the defining characteristics of keto and what differentiates keto from other ways of eating. Then we can examine indirect effects that occur due to factors such as weight loss. These are not unique to keto, though they might be more likely on a ketogenic diet compared to other ways of eating.

Carbohydrate Restriction

There is no real body of evidence that looks at ketogenic levels of carb restriction and menstruation, but there are some clues. In this small study, functional hypothalamic amenorrhea (FHA) was associated with dietary fat restriction; women with FHA actually ate non-significantly more carbs than matched controls and nearly identical total calories. Likewise, in this small study, FHA was associated with lower fat intake but no significant difference in carb intake.

This meta-analysis looked at the effect of low-carb (not keto) diets on markers of reproductive health among overweight women. The researchers found four studies that examined effects on menstruation; all showed improved menstrual regularity and/or ovulation rates. Of six studies that looked at levels of reproductive hormones, five reported significant improvements.

Carb restriction also results in decreased insulin production. Hyperinsulinemia and insulin resistance are frequently associated with polycystic ovarian syndrome (PCOS), one of the leading causes of female infertility and a frequent cause of menstrual irregularity. There is currently a lot of interest in using keto to treat PCOS, but only one small study has so far directly tested the effectiveness of a ketogenic diet to treat PCOS, with positive results.

Ketones

No studies have looked at the direct effects of ketones on menstruation.

Weight Loss

Of course weight loss is not unique to keto, but keto can be very effective for weight loss. Some women experience rapid weight loss when first starting a keto diet. Weight loss in and of itself can impact menstruation through a variety of pathways (and, of course, keto isn’t the only way people lose weight). A key way is by reducing the hormone leptin. Leptin’s main job is to communicate energy availability to the hypothalamus—high levels of leptin tell the hypothalamus that we have enough energy on board, which also means we can reproduce. Low leptin can disrupt the menstrual cycle and is linked to hypothalamic amenorrhea.

Body fat loss can also affect estrogen levels since estrogen is both stored and produced in adipocytes (fat cells). While fat loss in the long term will decrease estrogen production, it is possible that rapid fat loss might temporarily raise estrogen levels and can also affect estrogen-progesterone balance. These transient changes in estrogen levels might underlie some of the menstrual irregularities women report.

Stress

Stress can impact the menstrual cycle in myriad ways. Cortisol acts on the hypothalamus and pituitary glands, affecting hormone levels, sleep, immune function, and gut health, to name a few. Diets can be a source of stress, both at the physiological and psychological levels. Keto has a reputation for being especially stressful because it is more restrictive than other low-carb diets, but this can be mitigated by following the Keto Reset tips for women.

Thyroid Function

Thyroid dysregulation is another common cause of menstrual irregularities, and there remains a pervasive belief that keto is bad for thyroid health. Indeed, the thyroid is sensitive to nutrient deficiencies and caloric restriction, and thyroid hormones, especially T3, do frequently decline on keto. However, as Mark has discussed in a previous post, changes in T3 levels might not be a problem, especially in the absence of other problematic symptoms. Moreover, many practitioners now use keto as a cornerstone in their treatment of thyroid disorders.

What Should I Take From These Findings?

The first takeaway: there just isn’t much direct evidence about how keto might affect your menstrual cycle, positively or negatively. We have some studies suggesting that low-carb diets improve some aspects of menstruation and reproductive health, but keto is more than just another low-carb diet. Ketones themselves have important physiological properties, such as being directly anti-inflammatory, which might positively impact women’s reproductive health.

Second, the ways that keto is likely to (negatively) affect menstruation aren’t unique to keto, they’re common to any diet: hormone shifts mediated by energy balance, stress, and weight loss.

Furthermore, since keto is so often combined with caloric restriction, time-restricted eating, and fasting, even the anecdotal evidence might not be able to tell us all that much. If a woman is eating ketogenically, in a big caloric deficit, and doing OMAD (one meal a day), and her leptin plummets, how are we to know what really caused it? We don’t have good evidence that otherwise healthy women start a well-executed ketogenic diet and end up messing up their menstrual cycles.

That said, women do need to be cognizant of the sum total of the signals they are sending their bodies when it comes to energy availability and stress. A lot of women come to the keto diet with a history of adrenal, thyroid, metabolic, and reproductive issues. It’s important that they’re extra careful about how they approach keto. Done correctly, it might be just what the doctor ordered. I encourage any woman who’s dealing with other hormonal issues to work with a medical practitioner to tailor a keto diet to her unique needs.

But I’m Telling You, Keto Made My Period Go Haywire!

Ok, I believe you, really! But changes do not necessarily equal dysfunction. It is normal to experience hormone fluctuations when you make a massive—or even a relatively small but important—shift in your nutrition. Sometimes those fluctuations are unpleasant or unwanted, such as a period that lasts 14 days or one that arrives a week before you planned while you’re on vacation. However, that doesn’t make them bad from a health perspective. We need to respect that our bodies are dynamic systems. Changing the input will invariably change the output, and the system might need a few months to adapt to a new normal.

If your cycle goes wonky but you’re otherwise feeling good, give it a few months to sort itself out. If after a few months it’s still all over the place (or definitely if you’re having other disruptive symptoms), enlist help. In the meantime, check to make sure you’re not short-changing yourself nutritionally or calorically. Scale back on fasting efforts, and consider shifting more toward a traditional Primal way of eating.

At the end of the day, if you go keto and experience negative effects, stop. Keto is super hyped right now, but if your body is sending you clear signals that keto is not a good approach for you at this time, don’t do it. You can always try again later. It might be that your first attempt at keto didn’t work, but with a few adjustments and some experimentation over time you can find a version of keto that works for you.

Thanks for reading, everyone. Do you have comments, questions, or feedback? Let me know below.

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References:

Comninos AN, Jayasena CN, Dhillo WS. The relationship between gut and adipose hormones, and reproduction. Human Reproduction Update 2014; 20(2): 153–174.

Fontana R, Della Torre S. The Deep Correlation between Energy Metabolism and Reproduction: A View on the Effects of Nutrition for Women Fertility. Nutrients. 2016;8(2):87.

Klok MD, Jakobsdottir S, Drent ML. The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. Obesity Reviews 2007;8(1):21-34.

Meczekalski B, Katulski K, Czyzyk A, Podfigurna-Stopa A, Maciejewska-Jeske M. Functional hypothalamic amenorrhea and its influence on women’s health. J Endocrinol Invest. 2014;37(11):1049–1056.  

Tena-Sempere M. Roles of Ghrelin and Leptin in the Control of Reproductive Function. Neuroendocrinology 2007;86:229-241.

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Dear Mark: Antibiotic Recovery, Sprinting on Keto, Preparing for Bad Sleep

For today’s edition of Dear Mark, I’m answering three questions. First up, what can a person do to help their gut recover its barrier function after too many antibiotics? Are there any foods, supplements, or dietary strategies? Second, what can explain rapid fatigue during sprint sessions on a keto diet? Is this simply part of the deal, or are there modifications you can make? And finally, what do I do when I know I’m going to get a bad night’s sleep?

Let’s go:

Mark – any idea how to cure leaky gut caused by overuse of antibiotics. Tried raw dairy for a month to no avail.

First of all, check out my post on leaky gut. Read through it and follow my suggestions for preventing and treating intestinal permeability. It’s a great place to start.

Then, let’s look at some other interventions that have been shown to improve recovery from antibiotic therapy. While most of the studies referenced don’t explicitly describe antibiotic-induced leaky gut, anything that improves gut function and restores healthy gut bacteria will also normalize leaky gut—since it’s the eradication of native gut bacteria that causes antibiotic-induced leaky gut.

Fermented dairy. You tried raw dairy. What about fermented dairy? While raw dairy has its merits, it’s fermented dairy that just works for recovery from antibiotics. Yogurt is a good option to try, although the evidence is a bit inconsistent. Kefir is probably better; it’s been shown to improve patients’ tolerance to triple antibiotic therapy during treatment for H. pylori infection. This is even worth consuming during antibiotic therapy, as many of the probiotic bacteria found in fermented dairy show resistance to common antibiotics.

Fermented vegetables like sauerkraut are also must-eats. The fermented cabbage contains ample amounts of L. plantarum, a bacteria strain that’s been shown to prevent antibiotic-related diarrhea in piglets (another omnivorous mammal). Good options exist in stores (check the refrigerated section; shelf-stable pickles and kraut aren’t lactofermented), and even more are available in farmer’s markets, but the best way to get the most bacteria-rich vegetable ferments is to make your own.

Supplemental probiotics are fantastic here, too: large doses of the desired microorganisms delivered directly to your gut. Some of the strains used in Primal Probiotics, like B. clausii and S. boulardii, have been shown to be effective against antibiotic-related diarrhea, so that could be a good choice.

Don’t forget the food for your gut bugs: prebiotics. You need to eat fermentable fibers and other prebiotics like resistant starch to support the growth and maintenance of the helpful bacteria that improve gut barrier function. Consider eating cooked and cooled potatoes, unheated potato starch, leeks, garlic, onions, green bananas, apples, pears, berries, and pretty much any fruit or vegetable you can get your hands on. Plenty of them are low-carb enough to work on a keto diet, if that’s your desire. Oh, and dark chocolate is a great source of fiber and polyphenols, which have prebiotic effects in the gut.

Incorporate intermittent fasting. Going without food for a spell gives your gut a break and induces autophagy, which can help with tissue healing.

Get dirty, too, to introduce potentially helpful bacteria. Go out and garden. Go barefoot at the park (do your due/doo diligence, of course) and practice tumbling, or roughhouse with your kids (or friends). Don’t immediately rush to wash your hands all the time (unless you’ve been handling raw meat and/or dog poop).

Whatever you do, don’t stress too much about the antibiotics you had to take. Stress is awful for gut health and you’ve already taken the antibiotics—which were probably necessary—so that ship has sailed.

If probiotics with prebiotics aren’t helping (or making things worse), you might want to try going the opposite direction—removing all plant foods and doing a carnivore diet for a few weeks. While I have doubts about the long term viability and safety of eschewing all plant foods, enough people have written to me about their great experiences resolving gut issues with a bout of carnivory that it’s worth trying.

When on a strict keto plan, why do I become so quickly fatigued while attempting a HIT sprint workout?

The first five seconds of a sprint are primarily powered by phosphocreatine (or creatine phosphate), a “quick burst” energy source that burns hot but disappears quickly. This is the stuff used to perform max effort Olympic lifts, short sprints, and other rapid expressions of maximum power. It doesn’t last very long and takes a couple minutes to replenish itself. A keto diet doesn’t affect our creatine phosphate levels. If anything, it should improve them if we’re eating meat.

After five seconds, anaerobic metabolism of muscle glycogen provides the lion’s share of your energy needs. The longer your sprint, the more glycogen you’ll burn. The less glycogen you carry in your muscles, the shorter your sprint. Because once you run out of creatine phosphate and glycogen, you’re left with aerobic metabolism—great for longer distances, not so great for max effort sprints.

Keto dieters tend to walk around with less glycogen in their muscles. If that’s the case, longer sprints will be harder.

If you want to keep sprinting:

Do shorter sprints. Try a 10-second hill sprint rather than a 20-second one. Really go hard. Heck, you can even do 5-second sprints and derive major benefits; just do more of them and make sure to recover in between. There’s no rule saying you have to sprint for 20-30 seconds.

Take longer rest periods. Give your muscles a chance to replenish more creatine phosphate (and take creatine or eat red meat and fish, which are the best sources of dietary creatine).

Eat 20-30 grams of carbs 30 minutes before a sprint session. See if it helps. Alternatively, you can eat the 20-30 grams of carbs after the sprint session to replenish lost glycogen stores (without really impacting your ketone adaptation, by the way).

Most people figure out their sprinting sweet spot while doing keto. They may have to play around with the dosages, durations, and rest periods, but you can usually make it work. Be open to trying new permutations.

If you knew you were going to have a poor nights sleep, what measures would you take to reduce some of the damage?

I would exercise hard that night. Normally, a bad night’s sleep tanks your insulin sensitivity the next day, giving you the insulin resistance and glucose tolerance of a diabetic. A good hard interval session the night before a bad night’s sleep, however, counters the next-day insulin resistance.

I would make the most of it. Don’t dawdle. Don’t beat yourself up because of the impending sleep deprivation. It’s going to happen. You have to accept it, not let it destroy you.

Enjoy it. A little-known acute treatment for depression is sleep deprivation. That’s right: a single night of sleep deprivation has been shown to ameliorate depression in patients with clinical depression. Sometimes the effect lasts up to several weeks. It’s not a long term or sustainable fix for clinical depression, obviously, and you can’t do it every single night—chronic sleep deprivation is a major risk factor for developing depression—but it can improve your mood if you give in to it.

I would set out a jar of cassia cinnamon. I always add cassia cinnamon to my coffee in the morning after bad sleep; cassia cinnamon the day after a bad night’s sleep attenuates the loss of insulin sensitivity and glucose tolerance.

That’s it for today, folks. Thanks for writing in and reading! If you have any input on today’s round of questions, let me know down below.

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References:

De vrese M, Kristen H, Rautenberg P, Laue C, Schrezenmeir J. Probiotic lactobacilli and bifidobacteria in a fermented milk product with added fruit preparation reduce antibiotic associated diarrhea and Helicobacter pylori activity. J Dairy Res. 2011;78(4):396-403.

Bekar O, Yilmaz Y, Gulten M. Kefir improves the efficacy and tolerability of triple therapy in eradicating Helicobacter pylori. J Med Food. 2011;14(4):344-7.

Erginkaya Z, Turhan EU, Tatl? D. Determination of antibiotic resistance of lactic acid bacteria isolated from traditional Turkish fermented dairy products. Iran J Vet Res. 2018;19(1):53-56.

Yang KM, Jiang ZY, Zheng CT, Wang L, Yang XF. Effect of Lactobacillus plantarum on diarrhea and intestinal barrier function of young piglets challenged with enterotoxigenic Escherichia coli K88. J Anim Sci. 2014;92(4):1496-503.

Jitomir J, Willoughby DS. Cassia cinnamon for the attenuation of glucose intolerance and insulin resistance resulting from sleep loss. J Med Food. 2009;12(3):467-72.

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