Picture of olive oil and butter with post title: PKD Keto Diet: Is a keto diet a good idea for Polycystic Kidney Disease?

PKD Keto Diet: Is a Keto Diet a Good Idea for Polycystic Kidney Disease?

There is exciting research happening in the Polycystic Kidney Disease and nutrition world right now. Based on what we know know, should people with Polycystic Kidney Disease follow a keto diet? What are the benefits and risks of the PKD keto diet?

Keep reading to learn more!

What Is a Ketogenic Diet?

History of the Ketogenic Diet

A ketogenic (or “keto”) diet was developed to treat epilepsy in 1923 at the Mayo Clinic. The keto diet is still widely used today to effectively treat epilepsy in both children and adults who fail other medical treatments.(1)

Since then, the ketogenic diet has been studied as a treatment for obesity, Alzheimer’, other types of dementia, heart disease, PCOS, acne and many other health conditions with varying success. In addition, a simple Google search reveals that the ketogenic diet is (much of it falsely) touted to benefit nearly every health condition under the sun.

A True Ketogenic Diet

The original ketogenic diet developed in the 1920’s to treat epilepsy consists of 90% calories from fat, 6% from protein and 4% from carbohydrate. Because a diet this low in protein and carbohydrate is so difficult to follow, the classic ketogenic diet has been modified into many different versions. An example is the “modified” keto diet shown below. This version is 12% protein, 6% carbohydrate and 82% fat.(2)

Pie charts showing the percent of calories from protein, carb and fat on different low carb diets.  The classic keto diet is 90% fat, 6% protein and 4% carb.  The modified keto diet is 82% fat, 12% protein and 6% carb.  A "low carb" diet is 40% fat, 40% protein and 20% carb.  The diet recommended for kidney disease is 10% protein, 35% fat and 55% carb.

No matter the version, a hallmark of the ketogenic diet is a low carbohydrate intake. Carbohydrate is broken down to glucose, which is the primary source of fuel for our cells. When we stop eating carbohydrate (via a keto diet or starvation), the body creates ketones to use for energy instead of glucose.(2)

The amount of carbohydrate eaten must be very low to force our body to make ketones. Simply avoiding bread, pasta and sweets will likely not lower carbohydrate enough. To put your body in ketosis (the process of making ketones), you will need to avoid nearly all carbohydrate including all whole grains, fruit, sweets and many vegetables that contain small amounts of carbohydrate.

A true keto diet is also low in protein. Our bodies can make glucose out of protein. To be in true ketosis, a majority of your food must be from fat.

Keto Diet vs. Low Carbohydrate Diet

Due to the increase in popularity of the “keto” diet, the word “keto” is thrown around rather liberally. In diet culture, a “keto diet” has become synonymous with a low carbohydrate diet. There is no formal definition for a “low carbohydrate diet”. So, it has come to mean simply eating fewer high carbohydrate foods such as bread, pasta, fruit and sweets. And, often does not limit protein, which often results in very high protein intake. For the rest of this article, I use the term “low carb” diet to refer to this eating pattern.

Most Americans are eating too much refined carbohydrate.(3) This is primarily due to very large portions of white bread products and sugar. Think: big plates of pasta, large submarine buns, large cookies and desserts, huge piles of rice and 32oz sodas and sugary coffee drinks. However, healthy carbohydrates such as whole grain bread, whole grain pasta, quinoa, barley, oats or fruit are recommended to meet fiber and many vitamin and mineral needs.(4)

pictures of food on a keto diet (oil, butter, coconut oil, avocado, lettuce and salmon), low carb diet (steak, chicken, fish, berries, pepper and ham) and a kidney disease diet (kale, pineapple, beans, whole grain bread and lots of fruits and veggies(

Recent PKD Diet Research

It is fascinating time in PKD nutrition research. Many very interesting studies are happening right now to help us understand how diet can impact kidney cyst growth in PKD.

Calorie Restriction

Results from 2 studies in mice found that limiting total calorie intake by 10-40% slowed cyst growth. (5) (6).

Ketogenic Diet

In 2019, results from a study examining use of the ketogenic diet in rats with PKD was published. This study found that cyst growth was slowed in rats fed a ketogenic diet. The authors concluded that a specific ketone, beta-hydroxybutarate was the likely cause of slowed cyst growth.(7)

This study also found that ketosis induced by time restricted feeding and supplemental beta-hydroxybutarate slowed cyst growth in rats.(7)

Blood Sugar & Diabetes

Many other studies done in humans support the connection between high blood sugar levels and progression of PKD. We know that people with Type 2 Diabetes, who tend to have higher blood sugar levels, have larger cyst volumes. (8) Higher blood sugar levels have also been associated with bigger kidney cysts, but not necessarily with reduced kidney function.(9) We also know that bigger body size, which may be an indication of higher calorie and carbohydrate intake, is associated with faster progression of PKD.(10)

Concerns About a PKD Keto Diet

Cholesterol, Heart Health & Stroke

People who have Polycystic Kidney Disease are at very high risk of heart disease. A study found that nearly 90% of people with PKD had high blood pressure, about half had high cholesterol and a quarter reported some type of heart arrhythmia. Stokes and heart attacks are also more common in people with PKD. (11) In fact, people with PKD are most likely to die from heart disease. (12)

Because of the magnitude of heart disease risk, people with PKD have lower blood cholesterol targets. Goal LDL (low density lipoprotein lipids, or “bad cholesterol”) for people with PKD is less than 100mg/dL. Compared to the LDL goal for the general population of 130mg/dL.(13)

Therefore, a healthy diet for PKD must also be heart healthy. The American Heart Association (AHA) recommends no more than 5-6% of calories from saturated fat, or about 13 grams of saturated fat per day. In addition, AHA recommends including whole grains, and other fiber rich foods such as fruits and vegetables to help lower cholesterol (14). AHA recommendations are based on the best research we have for healthy eating to lower the risk for any type of cardiovascular event.

A ketogenic diet differs dramatically from nutrition recommendations for heart health. A true ketogenic diet is very limited in fruit, and even many vegetables to keep carbohydrate intake down. A keto diet allows no room for whole grain foods such as brown rice, whole grain pasta or bread. In addition, the very high fat content of a keto diet will inevitably provide excess saturated fat, compared to the AHA recommendations. Even heart healthy fats contain small amounts of saturated fat, which add up when consuming very large amounts.

 True Ketogenic DietTypical Low Carbohydrate DietHeart Healthy & PKD Diet Recommendations
VegetablesLimited

There is small amounts of carbohydrate in many vegetables. Vegetables are allowed, but the type and amount is restricted.
Most are includedEncouraged
FruitsEliminatedEliminatedEncouraged
Meat & ProteinLimited

Because your body can make glucose from protein, protein is restricted on a keto diet.
Unrestricted Small portions of lean or plant-based protein
FatUnrestrictedUnrestrictedLimited to 35% or less of calories. Replace saturated fats with heart healthy unsaturated fats.
Whole GrainsEliminatedEliminatedEncouraged
FiberLikely Inadequate

Without supplementation, it is very difficult to eat adequate fiber.
Likely Inadequate

Without supplementation, it is very difficult to eat adequate fiber.
Adequate

Fiber needs are met via whole grains, fruits, vegetables, nuts & seeds
Antioxidants & MicronutrientsLikely Inadequate

By removing fruits, vegetables and whole grains, it is very difficult to meet micronutrient needs and consume antioxidant rich foods without supplementation.
Likely Inadequate

By removing fruits, vegetables and whole grains, it is very difficult to meet micronutrient needs and consume antioxidant rich foods without supplementation.
Adequate

Whole grains, fruits and vegetables provide these compounds.

Kidney Stones

Kidney stones are are known complication of the ketogenic diet. (15) Low carbohydrate diets likely cause kidney stones due to excess protein and low intake of nutrients and compounds that stop kidney stones. In addition, a keto diet will cause urine to be more acidic, which is a risk factor for kidney stones.

A healthy diet for kidney stone prevention is remarkably similar to heart health and PKD diet recommendations. The kidney stone diet primarily focuses on controlled portions of protein, large amounts of fruits and vegetables, low sodium, low sugar and consuming enough dairy.

People with PKD are 10 times more likely to have kidney stones compared to people without PKD.(16) In addition to pain and inconvenience, kidney stones are associated with a higher incidence of kidney disease.(17) Given this very high risk, a healthy diet for PKD must also address kidney stone prevention.

Dietary Acid Production

It may be strange to think of food causing acid in your body, but there is a big connection! One of the kidney’s main functions is to get rid of excess acid. The food you eat is the biggest factor in how much acid your kidneys have to deal with.(18)

Acidosis is a condition where acid builds up in your body and is very common in kidney disease. Among many negative consequences, a primary complication of acidosis is faster progression of kidney disease. (19)

When your food is metabolized, it can produce either acid or base. Base helps neutralizes excess acid. Potential Renal Acid Load (or “PRAL”) is the fancy name for the amount of acid (or base) the food you eat causes during metabolism. (20) Protein (especially from animal protein sources) is the biggest contributor of acid in our diet. Fruits and vegetables produce base, and help reduce the amount of acid the kidneys need to get rid of. Generally grains, dairy and fat are near neutral – they do not produce much acid or base. Read more about PRAL.

Because the ketogenic diet is so restrictive in fruits and vegetables, it removes the opportunity to eat foods that produce base, or help neutralize acid. A true ketogenic diet that is high in fat would likely be neutral in terms of acid/base balance. A low carbohydrate, high protein diet (especially combined with restricted intake of fruits and vegetables) has a very high acid load.

Pictures of food that produces acid (steak, ham, chicken and fish), are neutral (or do not produce much either acid or base: milk, bread and fats) and foods that produce base (broccoli, carrots, berries and plums)

Fatty Liver

Nearly 80% of people with PKD have cysts on their liver. (21) Liver cysts are the most common manifestation of PKD other than kidney cysts and can impact liver function.(22)

Low carbohydrate diets are linked to Non-Alcoholic Fatty Liver Disease (NAFLD), primarily because of their very high fat content. NAFLD is the most common cause of liver transplantation in the Western world and can cause diabetes, heart disease and Chronic Kidney Disease. (23)

There is concern that a ketogenic diet could put people with PKD at greater risk of impaired liver function. This is especially concerning given the fact that NAFLD is connected with kidney disease.

Gut Microbiota

The gut microbiota, or the community of trillions of tiny bacteria that live in our intestines, is closely linked to health. Research has investigated the role these bacteria play in nearly every aspect of health including immunity, cancer, mental health, weight, heart health, vitamin production and even autism. Much more research needs to be done to fully understand the role of the microbiome for health. However, there is promising research in many fields.

The gut microbiota impact kidney disease too! The gut microbiota are linked to blood pressure, inflammation, altered nutrient metabolism and even progression of kidney disease.(24) Much more research needs to be done to determine the exact composition of bacteria that are beneficial for kidney disease. And, if strategies to change the microbiome such as probiotics, fecal transplantation or diet have an impact on disease outcomes. However, we know that a healthy gut microbiome is important for kidney disease.

Many studies have shown that low carbohydrate diets negatively impact the gut microbiota.(25) In general, a more diverse population of bacteria is healthy. One way to improve the diversity and amount of gut bacteria is to eat certain fibers, called “prebiotics”. Humans cannot digest these fibers. Instead, they pass through the gastrointestinal system and actually feed the bacteria in our gut. A keto diet harms the gut microbiome because it is difficult to get enough of these prebiotic fibers to feed gut bacteria.

Longevity

Of course, Polycystic Kidney Disease is a chronic disease. Treatment, especially nutrition, must be feasible to follow long term. A true ketogenic diet is highly restrictive and adherence to such a strict diet is difficult. In order to produce ketones and benefit from the PKD keto diet, people must follow a true ketogenic diet. Simply removing some carbohydrate or following a keto diet some of the time will not induce ketosis, and will likely not produce the proposed benefits.

In addition, following the keto diet for long periods of time heightens concerns about heart health, kidney stones, dietary acid production, fatty liver and changing the gut bacteria. We have no research to show that keto diets are safe for people with any kidney disease, much less for PKD specifically. Clinical trials are in progress to help us answer this question.

Whole Body Health

A healthy diet must address the health of the whole person: mind and body. A keto diet is deficient in many important healthy compounds such as fiber and many vitamins and minerals. These deficiencies increase risk of harm to many organs and body processes. Importantly, these deficiencies cannot be made up with supplements – supplements are never the same as real food.

Following a strict keto diet requires immense amount of time and planning. It makes eating at social gatherings difficult, which can cause a sense of isolation. This is especially a concern in people with PKD, as depression and anxiety are common.(26) The mental health impact of nutrition is a critical, often forgotten, factor in medical nutrition therapy.

Rats ≠ People

picture of a rat

Lastly, I think it is important to consider the differences between animals and humans. The only studies we have showing the possible benefits of a PKD keto diet are in animals. Animal models are not a perfect representation of humans. Many trials done in animals fail to show the same results in humans. It is unknown if the benefits of the PKD keto diet are the same in people. Perhaps more importantly, the side effects of people with PKD following a keto diet are not known.

Jumping to conclusions from animal studies to humans also requires the ability of humans to follow a diet. Before formal nutrition recommendations can be made, we need more research to show the feasibility and safety of following a PKD keto diet long-term.

The PKD Keto Diet: My Recommendation

Although there is very interesting research happening right now on the PKD keto diet, I have many concerns. I do not think that the research is strong enough to routinely recommend a true ketogenic diet for people with PKD right now.

We need research (and a lot of it) in humans before I would feel comfortable recommending a keto diet to treat Polycystic Kidney Disease. Some of the questions about a PKD keto diet are:

  • What level of ketosis needs to be achieved for benefit in PKD? This will help us determine how low in carbohydrate diets must be for benefit.
  • Are there any harmful effects of ketones for people with PKD? Does this differ by level of kidney function?
  • Does a ketogenic diet further increase the risk of cardiovascular disease, kidney stones and impaired liver function in people with PKD?
  • Are people with PKD able to stick with a keto diet long term? If so, are there any unanticipated side effects or risks associated with long-term adherence to a keto diet?
  • Does supplementing beta-hydroxybutarate reduce cyst growth in PKD in humans? If so, what is the dose required to see benefit? Are there side effects of this supplementation.

Because the keto diet is in direct contradiction of the best science we have for treating kidney disease with nutrition, I need answers to these questions before I recommend it for PKD.

That being said, science (and subsequent nutrition recommendations) change over time. Perhaps I will be recommending a keto diet to all people with PKD in a few years. Who knows!? But right now, the risks outweigh the known benefits in my opinion.

What Should People with PKD Eat?

We know that many aspects of nutrition are related to cyst growth in people with PKD. Notably, a high fluid and low sodium diet have been shown to slow cyst growth. For most people, 3 liters of fluid per day will inhibit hormones that are associated with faster cyst growth.(27) (28) (29)  Limiting sodium to about 2,300mg per day may also slow the growth of kidney cysts.(30) (31

Rather than a true keto diet, I do think it makes sense to limit large amounts of refined carbohydrate and keep added sugar to a minimum. These changes will help reduce your risk of high blood sugar, which has been associated with faster progression of PKD.(9) These changes will also help control calorie intake.

In addition, avoiding added sugar and choosing whole grains can help reduce the risk of heart disease. Choose primarily whole grain carbohydrates such as whole grain bread, whole grain pasta, brown rice, quinoa, wheat berries, barley, bulgur or farro. Portion sizes are different for everyone, but a serving of around 1 slice or 1/2 cup is a good starting point. The American Heart Association recommends limiting added sugar to no more than 25g per day for women and 38g per day for men. (14)

Make sure to read my overview of healthy eating for Polycystic Kidney Disease. I also have an example PKD menu, which includes recipes!

Healthy eating for PKD also is highly dependent on your level of kidney function and lab values. A healthy PKD diet for someone who has very low kidney function and high blood potassium is very different than a healthy diet for someone with PKD and good kidney function. Always talk to your doctor and dietitian who know your medical history to figure out what healthy eating looks like for you!

Happy Eating!

Melanie

For more Polycystic Kidney Disease support, check out my Polycystic Kidney Disease Facebook Community!

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