Is Keto Safe While Breastfeeding?

Updated: Mar 12

Everyone seems to have an opinion on the keto diet these days. People are either strongly against it, or swear by it. It’s touted as both the miracle diet to make us superhumans, as well as a surefire way to get yourself killed by way of ketoacidosis.


Frankly, I don’t care if a healthy, grown adult who is neither pregnant nor lactating goes keto (preferably under medical supervision). I’ll be the first to congratulate them if it works out and they achieve their goals with keto. In fact, I’m intrigued by the physiology and reported positive effects myself. And since I like to label myself a functional and integrative-focused Dietitian, I’m absolutely open to ‘alternative dieting’.


With that out of the way, let’s get to the actual point of this blog article. You see, I’ve also come across countless articles, YouTube videos and social media posts touting keto as a safe diet to lose weight while breastfeeding, starting with Jenna Jameson’s Instagram post:



Jenna claims that "From my experience it (the keto diet) ABSOLUTELY is (ok while breastfeeding). My supply is healthy and strong, I haven't seen any dips in supply, letdowns, or in Batellis reaction to taste."


Now, let me make one thing clear before moving forward: “Making enough milk” is NOT the only indicator of a healthy mom & baby! How much milk you make matters, but what also matters is your milk’s content of nutrients & other functional goodies, other substances which reach your milk that may be harmful, your own nutrient status, your own microbiota and, let’s not forget, your own mental and physical wellbeing. Just because Jenna still makes enough milk on keto, doesn’t make the keto diet safe while breastfeeding.







“So, Marina, are you saying the keto diet is bad?”


Not at all, in fact…



1. The Keto Diet Has Health Benefits (for Certain Conditions)

The keto diet is a high fat, low carb diet which shifts your body's metabolism into producing ketones as fuel (as opposed to glucose on a standard diet). Essentially, your carbohydrate intake is so low on this diet (about 20 grams per day) that your body starts turning fat into ketones in order to continue fueling its organs with energy (especially the brain, which can only use glucose or ketones as fuel).(1)

Normal ketone levels are generally under 0.5 mmol/L. Once your ketone levels increase above that threshold (this can happen from fasting, several days on a keto diet, OR metabolic dysregulation), you are in so called 'ketosis'. Ketosis is essentially when your body's ketone levels are between 0.5 and 3 mmol/L (some say up to 5 mmol/L). Some call this state 'nutritional ketosis' to suggest this is when the body is most effective at burning fat and experiences health benefits.


Indeed, more and more studies are coming out with some significant health benefits of 'ketosis' for certain conditions:


  • The keto diet seems to be an effective way to prevent seizures in epileptic children (2, 3,)

  • It appears to have a positive effect on other diseases affecting the brain, such as Alzheimer's, Parkinson's and amyotrophic lateral sclerosis (4, 5, 6)

  • It may be a novel approach to treating cancer (6, 7)

  • It can lead to weight loss (8, 9)

  • It may improve insulin sensitivity and glucose control in some diabetics (8) (it’s important to mention here that diabetics are at high risk of diabetic ketoacidosis, so diabetics should absolutely not go keto unless advised to do so by their doctor and under strict medical supervision)

Note that all of the studies above were done on non-lactating, non-pregnant patients.







2. Ketosis is not the same as Ketoacidosis, but....


As discussed before, "keto" is called "keto" because you have ketones in your blood. This state is called "Ketosis". KetoACIDosis is another metabolic state where your blood's pH level decreases to dangerous levels, from the build up of ketones. This can quickly lead to coma and death.


The biggest argument I always see on pro-keto websites defending the safety of the keto diet is that Ketosis is not the same as Ketoacidosis.


That is true, but consider that the difference between ketosis and ketoacidosis is merely the amount of ketones in the blood.


Ketosis: Your ketone levels are between 0.5 to 3.0 mmol per liter. Your blood's pH level is not affected by it (yet).


Ketoacidosis: Your ketone levels are above 3.0 mmol per liter, which lowers your blood’s pH level. Your blood is becoming acidic, which is life threatening and must be treated immediately because even small shifts in the blood's pH level can lead to vomiting, coma and/or death very quickly (10).

“So, if the difference between ketosis and ketoacidosis is merely the amount of ketones in the blood, wouldn’t everybody end up in ketoacidosis following a keto diet? How come some people can live on keto for months or even years”– smart question!


The answer is that most of us have enzymes in place which break down ketones, and this is often enough to keep us out of ketoacidosis (38).


However, there are a few different ways you can still end up in ketoacidosis:


1. If you have a genetic mutation which makes your body produce none or less of the enzymes that break down ketones, you are at high risk for ketoacidosis (11).


2. If you have uncontrolled diabetes. The lack of insulin means the body’s cells can’t use glucose and so the body resorts the producing ketone bodies in order to continue fueling the brain and other tissues. This is called ‘diabetic ketoacidosis’ (DKA) and is probably the most common form of ketoacidosis.


3. If you have been binge-drinking for longer periods of time with little intake of carbohydrates, you may go into ‘alcoholic ketoacidosis’ because your body produces excessive ketones and lactic acid as a result of the excessive alcohol intake. 12, 13,


4. If your body is in metabolic stress from starvation, illness, excessive exercise (14, 15, 16,)


5. If you are pregnant or breastfeeding, your body is at increased risk for ketoacidosis (17, 18, 19, 20, 21, 22, 23 ,24,25), possibly due to hormonal changes and/or increased metabolic demand of pregnancy and lactation





3. Pregnancy and Lactation puts you at Risk for Ketoacidosis (the Science)


We just learned that the difference between ketosis and ketoacidosis is essentially the amount of ketones in the blood. Generally, if the amounts are higher than 3-5 mmol/L, the blood's pH level will lower (acidify), which is life threatening. Frankly, research has shown that this is rare in healthy, non-pregnant and non-lactating adults. That is because most people have enzymes in place which oxidize ketone bodies fast enough so they don't increase to dangerous levels (11).

However, the chances of ketoacidosis seems to increase if the body is also dealing with certain physiologic stressors. This can be in the for of an illness, excessive exercise, uncontrolled diabetes, alcoholism, but it can also be pregnancy or lactation!


Lactation and pregnancy can be "stressors" on the body which can quickly turn ketosis into ketoacidosis.

Several cases have been reported in the literature:

  • A 35 year old breastfeeding mom (5 months postpartum) was diagnosed with lactation ketoacidosis following a sugar, gluten and dairy free diet (15).

  • A 22 year old tandem breastfeeding mom (4 months old and 30 months old) was on a restricted calorie diet (it is not reported if it was low carb). She was diagnosed with breastfeeding ketoacidosis (16).

  • A 24 year old breastfeeding mom (18 weeks postpartum) was diagnosed with lactation ketoacidosis. She had been following a strict ketogenic diet (17)

  • A 27 year old breastfeeding mom (8 weeks postpartum) was diagnosed with lactation ketoacidosis. She had been following a low carbohydrate diet (18).

  • A 32 year old breastfeeding mom (8 weeks postpartum) developed pneumonia while following a ketogenic diet. She developed life threatening lactation ketoacidosis. (19).

There are several more reported cases, see a selection of them in this systematic review here (10).

Sidenote: I find it ironic that many of the above mentioned studies are titled 'a rare case of lactational ketoacidosis', or 'an unusual occurrence of lactational ketoacidosis', when apparently, it isn't so rare at all. Consider that these are just the cases that were correctly diagnosed and they decided to write case studies about, when there are likely many more being treated at emergency rooms around the world which are either not correctly diagnosed or do NOT end up in a medical journal. Also, since the keto diet has just recently become trendy, we may start to see more of this.



4. “But Jenna Jameson is doing it!”



You may be thinking to yourself: “I’ve heard of plenty of moms doing the keto diet while breastfeeding, and they are doing just fine”.


First of all: You are not Jenna Jameson, nor any other mom on Instagram, for that matter. You have your own body, your own hormones, your own set of stressors, your own physiology. Just because it works for them, doesn’t mean it’ll work for you. It may, but it may also not and get you hospitalized or worse. Is it worth the risk?


Secondly: Those moms telling you they are doing keto while breastfeeding, how can you be sure they are truly on a keto diet, and not just on a ‘low carb’ diet? Low carb is completely different from keto much less dangerous. I often plan low carb diets for my lactating weight loss clients, but I make sure to include enough carbs to prevent excessive ketone production.


Thirdly: What stage of lactation are those moms in that tell you they are doing keto while breastfeeding? Are they feeding a toddler once in a blue moon, or do they have a 3-month-old they are feeding round-the-clock? The metabolic demand of lactation can be very different, depending on the stage of lactation you are in, and the risk of ketoacidosis while breastfeeding is likely higher, the more you breastfeed.




5. The Keto Diet Can Put You At Risk For Nutrient Deficiencies



The keto diet (if done right!) can be a very nutrient dense diet! Grass-fed beef, pastured eggs, salmon, nuts, seeds, kale & broccoli….oh, a Dietitian’s dream! You’ll get tons of important nutrients on such a diet, including omega-3's, zinc, Vitamin D, choline, iron and more.

However, fruits, grains, starchy vegetables and beans also have a specific set of nutrients which are not quite as abundant in meats, eggs and non-starchy vegetables. Couple that with the fact that most of your nutrient requirements are increased during pregnancy and lactation, and you may end up with a nutrient deficiency (or decreased levels of these nutrients in your milk) despite your nutrient-dense diet.

Critical nutrients on a keto diet:


  1. Fiber: Fiber is important for a healthy gut and bowel movements, primarily for mom. However, since more and more studies are coming out suggesting mom is sharing her gut microbiome with baby while pregnant and breastfeeding (26), you may affect not just your own, but also your baby's microbiome if you are eating a low-fiber diet.

  2. Vitamin C: Fruits, which are limited on a keto diet, are an important source of Vitamin C. Yes, you could get your Vitamin C from bell peppers and broccoli instead, but it is just so much more difficult to meet your daily needs (which are increased while pregnant or breastfeeding!) if you are restricting entire food groups. Vitamin C is one of those nutrients that does decrease in your breast milk if your intake is deficient (27), and signs and symptoms of a Vitamin C deficiency can range from a simple rash to a medical condition called scurvy (28). Most concerning to me these days is that a Vitamin C deficiency can also decrease your and baby's immunity (29).

  3. Thiamine (Vitamin B1) is another Vitamin which is more difficult to get enough of on a keto diet. I'm not going to say you WILL be thiamine deficient on a keto diet, because beef and salmon also contain some Vitamin B1. However, it's just easier to meet your daily (increased) thiamine requirements if you also eat whole grains, and levels in breast milk decrease if you are eating a Vitamin B1 deficient diet (27).

  4. Potassium: Good sources of potassium are beans, potatoes, sweet potatoes, bananas, oranges and fruit in general, all off limits on a keto diet. Your intake requirements are higher while pregnant/breastfeeding, so it's hard to get the necessary amount of this important mineral on a keto diet.

  5. Electrolytes & Fluids: Last but not least, the keto diet has a diuretic effect when first started, which means your body will 'flush out' fluids and electrolytes when switching to this type of eating. Especially while breastfeeding, this can easily lead to dehydration and electrolyte imbalances. While the mineral content of breast milk isn't as affected by mom's diet, eventually, dehydration and electrolyte imbalances can decrease your milk supply.



5. The Keto Diet Can Change Your Microbiome






This is where it gets really interesting! I haven’t really seen anybody talk about the changes to the gut microbiome following a keto diet. This, however, may just be the most significant piece to the puzzle, since our gut microbiome affects so many aspects of our health, including weight gain/loss and risk for disease.


Plus: Did you know that you are likely sharing your gut microbiota with your baby while breastfeeding through the so called entero-mammary pathway? ( )


Contrary to popular belief, the gut microbiota is less affected by the probiotic pills we pop and more influenced by the foods we eat on a daily basis. That is because the good and bad bacteria in our gut need food to thrive. Some do better with sugar, while others thrive on a high fat diet. In any case, the foods we eat affects our gut flora. (30, 31, 32)!


It makes sense then to investigate whether the keto diet, which obviously is a very extreme diet with a lack of carbohydrates, fiber and sugar and high amounts of fat, changes one’s gut microbiota.


Research is right in the middle of it, so I can't give you a definite answer yet on whether the keto diet has a positive or a negative effect on the gut flora.


Some studies show it may decrease overall diversity of the gut microbiome, other studies show it decreases certain bad bacteria and increases certain good bacteria, while again other studies show the opposite. Again others show that it may only change in those patients who actually have an imbalance. A good review article can be found here (33).


Confused yet?


It's possible the effects of the ketogenic diet on the gut microbiome depend on the overall picture: What is your individual microbiome blueprint? Are you taking probiotics, and which type? What 'type' of keto diet are you eating? The type that comes with lots of processed foods and trans fats (likely bad for the microbiome) or are you eating a keto diet rich in omega-3 fats, plant based proteins and phytonutrient (likely good for the microbiome)?


Overall, it's too early to say whether the changes to the gut microbiome on a keto diet are good or bad.



6. Your Mental Health is Important, Too!


Something I probably don't talk about often enough is mental health. I do feel it's important to mention here, because it's an important part of the equation.


Breastfeeding is tough. Motherhood is tough. Eating healthy is tough. Losing weight is tough, Heck, this stage of life is tough in general.


The last thing you need right now is a stressful diet. The keto diet can be very stressful. It can be frustrating. It can be isolating. You may not enjoy it as much as others (who are making a profit from it) seem to be.


You may be craving some ice cream, some potato chips, or a hearty noodle dish.


Eat it! You deserve it. If it benefits your mental health, I'd consider it 'healthy', too!



7. My Verdict


In summary: No, I would not recommend the keto diet while breastfeeding.


I am aware there may be some health benefits to the keto diet and it's a trendy way to lose weight; however, there are also some serious risks, the extent of which we do not 100% understand yet.


Despite what you've been told, the risk of ketoacidosis is increased on a keto diet if you are breastfeeding or pregnant. It's 'metabolic stress' on the body, which can lead to ketone bodies increasing to dangerous levels. Several case studies of this happening are listed in section 3, and just because 'others have done keto while breastfeeding and were fine', doesn't make it safe for you.


There is also the risk of nutrient deficiencies (which may also decrease levels in breast milk), and the risk of dehydration/electrolyte imbalances.


Your microbiome (and your baby's!) may also change on a keto diet, which can be either good or bad. We just don't know enough about the effects of keto on the microbiome yet (hopefully, more research will come out soon).


It's also a tough diet, and the last thing you need in the postpartum stage is more stress!


If you really want to try the keto diet, try it later.


Try it when you're done breastfeeding. When there's more research on it. When we know more about its effects on the microbiome. Right now? I wouldn't put that extra stress on me and I wouldn't risk it. It's not worth it, since there are other 'safe' ways to lose weight while breastfeeding.


Contact me if you want me to plan out such a diet for you, that will help you lose weight safely while breastfeeding!



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