The PKD Diet: Healthy Eating for Polycystic Kidney Disease

The PKD Diet: Healthy Eating for Polycystic Kidney Disease

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A healthy diet can have a huge impact in Polycystic Kidney Disease.  Even if you have normal kidney function, it is never too early to start learning about what you can do to slow the progression of Polycystic Kidney Disease with diet.  In fact, many of the patients I see wish they knew about the PKD diet sooner and that they could do something to stop disease progression. 

The PKD diet is overall a healthy diet that focuses on eating lots of fruits and vegetables, while limiting large amounts of salt, sugar and protein.  Keep reading to learn about the specifics and the science behind the PKD diet.

What is PKD?

PKD stands for “Polycystic Kidney Disease”.  PKD is a hereditary health condition that affects about 12.5 million people worldwide and is the cause of 10% of End-Stage Kidney Disease (ESRD) that requires dialysis. It is the most common hereditary disorder that affects the kidney. (1)

PKD is characterized by large cysts on the kidney.  These cysts generally start small and continue to grow over many years.  Eventually, these cysts impact kidney function and people with PKD will need to start dialysis or get a kidney transplant.  How quickly the cysts grow and how fast kidney function declines is very different between people.  Some people will need dialysis or a transplant early in life, and others will never need these treatments.  Your nephrologist (or kidney doctor) is the best person to help you understand the severity of your PKD diagnosis.

PKD can be inherited with dominant or recessive genes.  If it is inherited dominantly, PKD is called “Autosomal Dominant Polycystic Kidney Disease”, or “ADPKD”.  If PKD is inherited via recessive genes, it is called “Autosomal Recessive Polycystic Kidney Disease”, or “ARPKD”.  Generally, ARPKD is much more severe than ADPKD and is much less common.  Nutrition and healthy eating are the same for both ARPKD and ADPKD. (2)

The cysts on kidneys can get very large.  The cysts are filled with fluid, making them very heavy, up to 30 pounds.  It is common for cysts to develop on other organs.  Most commonly, cysts can develop on the liver and pancreas. (3)

Why Is Nutrition Important for People with PKD?

Nutrition is important for people with PKD for many reasons.  A healthy diet may help slow the growth of cysts, ultimately slowing decline of kidney function.  In addition, healthy eating can help control side effects and common conditions related to PKD such as high blood pressure, edema, acidosis, heart health, stroke and kidney stones. A healthy PKD diet can help with all of these factors. (3)

Sodium in the PKD Diet

As with all people, eating too much salt (or sodium) can raise blood pressure.  This is especially important for people with PKD as high blood pressure can damage kidneys.  In fact, high blood pressure is the second cause of Chronic Kidney Disease (CKD) in the United States. (4)  Also, as kidney function declines, your body has a harder time controlling blood pressure.  High blood pressure (aka “hypertension”) is both a cause and symptom of kidney disease, so is an important consideration for everyone with PKD.

A lower sodium intake has been associated with slower kidney cyst growth in people with PKD. (5) (6) Slower cyst growth is likely due to lower amounts of a hormone called vasopressin (aka “anti-diuretic hormone” or “ADH”).  When you eat too much salt, the amount of salt in your blood goes up a small amount.  To correct the higher blood sodium, your body needs to keep extra water on the body to dilute that sodium.  This is where vasopressin comes in.  Vasopressin causes your body to retain water and bring the sodium level in your blood back to normal.  In animals with PKD, higher vasopressin is associated with faster cyst growth. (7) (8) Bottom line, eating too much salt increases the hormone vasopressin, which is tied with faster growth of kidney cysts in PKD.

Sodium is a key piece of the PKD diet. But, how much sodium is safe to eat?  It is both impossible and unhealthy to cut sodium completely out of your diet.  Some sodium is necessary for your body to function properly!  The problem is that most of us are eating way more than we need.  The National Kidney Foundation recommends limiting sodium to no more than 2300mg per day. (9) This is about the amount of salt in 1 teaspoon. 

It is important to remember that most (around 80%!) of the salt in our diet comes from processed foods – where the salt is already added to the food.  Just people you do not add salt to your food does not mean your diet isn’t high in sodium.  Pay close attention to the sodium in the foods you eat from restaurants, frozen foods, canned, bottled and convenience foods to limit how much salt you eat.  The salt in processed foods adds up quickly! Because the average diet in the United States is so high in processed foods, the average sodium intake is more than double what we should be eating: closer to 6,000-7,000mg per day!

Fluid in the PKD Diet

A common recommendation for people with PKD is to drink water.  A lot of water.  Most healthcare professionals recommend a goal of 3 liters of fluid per day.

The science behind a high fluid intake is similar to the recommendation to limit salt.  Consistently drinking a lot of fluid will reduce how much vasopressin your body needs to retain water.  We know that vasopressin is linked to slower kidney cyst growth in animal research. (7) (8)  Both animal and human research has shown that drinking lots of fluid can reduce vasopressin in animals with PKD. (10) (11) (12)  Research is ongoing to figure out if reduced vasopressin from high fluid intake translates to slowed decline in kidney function and cyst growth.

Most of your fluid intake should be from good ol’ water.  However, drinking 3 liters of plain water everyday can get boring!  Many of my patients find it helpful to experiment with infused water.  Cut up your favorite fruit and let it sit in a pitcher of water in your refrigerator overnight.  Unsweetened flavored waters like LaCroix*, Spindrift* or Bubly* are also wonderful option to mix it up from time to time.

Some people find that using a “smart” water bottle helps them meet their daily fluid goal. The HidrateSpark* water bottle connects to a phone app and actually tracks how much water you drink and reminds you to drink more when you fall behind.

Be careful to avoid drinks large amounts of sugar like regular soda, lemonade, juice, punch or sweet tea.  This sugar (and calories!) can add up quickly! 

What about coffee and tea?  There hasn’t been any research showing that drinking a reasonable amount of caffeine is harmful in PKD.  I recommend no more than 1-2 cups of coffee or tea per day.  Again, just be careful with how much sugar you add with flavored coffee creamers and “fancy” coffee drinks!

Protein in the PKD Diet

The type and amount of protein that is right for people with kidney disease is a hot topic!  Unfortunately, there hasn’t been a lot of research in protein and PKD specifically.  One study showed that restricting protein in people with very low kidney function (GFR less than 13 ml/min) was beneficial, but not for people with higher levels of kidney function. (13)  However, another study didn’t find any benefit in patients with PKD. (14)  We need much more research to know what is best for the PKD diet.

Amount of Protein

Given the lack of research in PKD patients, I default to the protein recommendations from the National Kidney Foundation.  For most people I see with PKD, I recommend a total protein intake of 0.8 grams of protein per kilogram body weight.(9)  This translates to about 0.36 grams of protein per pound of body weight.  This might be different depending on your kidney function or medical history.  Always ask your dietitian what is best for you specifically.  

Type of Protein

Over recent years, there has been a lot of research investigating the type of protein that is best for kidney disease.  We now know that plant proteins are less harmful to our kidneys compared to animal proteins.(15)  This likely largely due to the lower acid LINK plant proteins produce compared to animal proteins.

Again, little research has been done looking at this topic in PKD patients specifically, so we must go with the recommendations for general kidney disease.  Limiting meat, poultry, fish and seafood and replacing these foods with plant proteins like beans, nuts, lentils and whole grains may slow the progression of kidney disease.  Some patients choose to follow an entirely vegan or vegetarian diet, while others choose to cut back animal protein to once per day.  Talk with your dietitian to learn what is best and realistic for you!

Potassium is a common concern about plant proteins in a kidney healthy diet.  However, not all patients with kidney disease need to limit potassium.  In fact, a high potassium diet is beneficial kidney patients with normal kidney function. Traditional kidney diets do not allow many healthy plant based protein foods like beans and seeds due to their phosphorus content.  We now know that only about 50% of the phosphorus in these foods is absorbed, whereas much more is absorbed from meat and other animal sources of phosphorus.(16) Plant based proteins can be safely incorporated into kidney friendly diets.

Heart Health and Polycystic Kidney Disease

Patients with PKD are at high risk of heart diseases such as hypertension, high cholesterol, peripheral vascular disease and stroke.(17) In fact, the most likely cause of death for people with PKD is heart disease.(18)  Given the higher risk of heart disease, general heart healthy diet recommendations are very important for the PKD diet.

The American Heart Association recommends a diet that includes: (19)

  • A variety of fruits and vegetables (aim for at least 5 servings per day)
  • Whole grains (healthy examples are whole grain pasta, whole grain bread, brown rice, quinoa, barley, farro, oatmeal and bran)
  • Low-fat dairy products (skim milk, low fat or fat free plain yogurt, fresh low sodium cheeses such as mozzarella)
  • Nuts and legumes (beans, lentils and seeds)
  • If you eat animal protein, choose fatty fish twice per week (salmon and tuna are great picks!) and lean chicken or turkey without the skin
  • Non-tropical oils (olive, canola, avocado or sesame oil are tasty choices!)
  • Limited amounts of saturated fat (butter, baked goods, fried foods), sugar and salt
  • Alcohol only in moderation if you choose to drink.  No more than 1 drink per day for women and 2 drinks per day for men.

The “Dietary Approaches to Stop Hypertension” (DASH) diet is recommended by the American Heart Association and is in line with PKD diet recommendations as well. The DASH diet is very high in fruits and vegetables (8-10 servings per day!), focuses on plant proteins, low-fat dairy and limiting sugar and saturated fat.

Ketogenic Diet and Polycystic Kidney Disease

Ketogenic diets in PKD has become a very popular topic.  In 2019, a fascinating study was published that showed slowed cyst growth in rats with PKD with a ketogenic diet.(20)  In this study, cyst growth was also slower in the rats who practiced intermittent fasting.  Your body makes ketones for fuel when you follow a strict ketogenic diet, or go a long time without eating.  Beta-hydroxybutyrate is a specific ketone that is suspected to be beneficial in this study.

We need much more research on this topic before recommendations can be made for people with PKD.  Diet recommendations should not be made on one study, nor without research in humans.  A true ketogenic diet that causes ketone production must be very high in fat.  We know very high fat diets are harmful to the heart.  This is very concerning for people with PKD because they are at much greater risk of heart disease and stroke.(18

In addition, keto diets are often much higher in protein than the recommendation of 0.8 grams per kilogram body weight.  We know thigh protein diets can quicken kidney disease progression to dialysis and exacerbate acidosis, a side effect of kidney disease.(21)  Because of these known risks, I do not recommend ketogenic diets to people with PKD. 

This is a fascinating area of research and hopefully I will be able to give more recommendations in this area soon. Right now, the risks of a ketogenic diet do not outweigh the possible benefit.

Summary of the PKD Diet

Whew!  You made it.  There is a lot to know about healthy eating for PKD – and a lot more scientists need to learn.  It can be overwhelming trying to pull all this information together into a healthy eating plan. 

I’ll try to simplify this article as much as possible.  Here is a summary of all my recommendations for people with PKD:

  • Sodium. Limit to 2,300mg per day.
  • Protein. Limit to 0.8grams per kilogram body weight. Try to choose more plant proteins like beans, lentils, nuts and legumes.  Limit animal proteins.
  • Fluid. Drink 3 liters per day.
  • Fruits & Vegetables. Really work on increasing how many fruits and vegetables you eat.  Aim for at least 5 servings per day.  More is better!
  • Whole Grains. Choose mostly whole grains rather than refined grains like sugar and white bread.
  • Fat. Choose healthy fats like olive or canola oil.  Limit saturated and trans fat.
  • Sugar.  Limit added sugar from foods like cakes, cookies and sweetened drinks.
  • Live a Healthy & Happy Life!  Do not smoke.  If you choose to drink alcohol, drink in moderation. Be physically active; find ways to move your body regularly that feels good!  Work on controlling stress and be mindful of your mental health; this is something we could all do better!

Happy Eating!

Melanie

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

References

1. Spithoven EM, Kramer A, Meijer E, et al. Renal replacement therapy for autosomal dominant polycystic kidney disease (ADPKD) in Europe: prevalence and survival–an analysis of data from the ERA-EDTA Registry. Nephrol Dial Transplant Off Publ Eur Dial Transpl Assoc – Eur Ren Assoc. 2014;29 Suppl 4:iv15-25. doi:10.1093/ndt/gfu017

2. Chapman AB, Devuyst O, Eckardt K-U, et al. Autosomal-dominant polycystic kidney disease (ADPKD): executive summary from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference. Kidney Int. 2015;88(1):17-27. doi:10.1038/ki.2015.59

3. Di Iorio BR, Cupisti A, D’Alessandro C, Bellasi A, Barbera V, Di Lullo L. Nutritional therapy in autosomal dominant polycystic kidney disease. J Nephrol. 2018;31(5):635-643. doi:10.1007/s40620-018-0470-x

4. Kidney Disease: Causes. National Kidney Foundation. Published December 24, 2015. Accessed June 25, 2020. https://www.kidney.org/atoz/content/kidneydiscauses

5. Torres VE, Grantham JJ, Chapman AB, et al. Potentially modifiable factors affecting the progression of autosomal dominant polycystic kidney disease. Clin J Am Soc Nephrol CJASN. 2011;6(3):640-647. doi:10.2215/CJN.03250410

6. Torres VE, Abebe KZ, Schrier RW, et al. Dietary salt restriction is beneficial to the management of autosomal dominant polycystic kidney disease. Kidney Int. 2017;91(2):493-500. doi:10.1016/j.kint.2016.10.018

7. Wang X, Wu Y, Ward CJ, Harris PC, Torres VE. Vasopressin directly regulates cyst growth in polycystic kidney disease. J Am Soc Nephrol JASN. 2008;19(1):102-108. doi:10.1681/ASN.2007060688

8. Gattone VH, Wang X, Harris PC, Torres VE. Inhibition of renal cystic disease development and progression by a vasopressin V2 receptor antagonist. Nat Med. 2003;9(10):1323-1326. doi:10.1038/nm935

9. National Kidney Foundation. KDOQI Clinical Practice Guideline for Diabetes and CKD: 2012 Update. Am J Kidney Dis. 2012;60(5):850-886. doi:10.1053/j.ajkd.2012.07.005

10. Hopp K, Wang X, Ye H, Irazabal MV, Harris PC, Torres VE. Effects of hydration in rats and mice with polycystic kidney disease. Am J Physiol Renal Physiol. 2015;308(3):F261-266. doi:10.1152/ajprenal.00345.2014

11. Barash I, Ponda MP, Goldfarb DS, Skolnik EY. A pilot clinical study to evaluate changes in urine osmolality and urine cAMP in response to acute and chronic water loading in autosomal dominant polycystic kidney disease. Clin J Am Soc Nephrol CJASN. 2010;5(4):693-697. doi:10.2215/CJN.04180609

12. Higashihara E, Nutahara K, Tanbo M, et al. Does increased water intake prevent disease progression in autosomal dominant polycystic kidney disease? Nephrol Dial Transplant Off Publ Eur Dial Transpl Assoc – Eur Ren Assoc. 2014;29(9):1710-1719. doi:10.1093/ndt/gfu093

13. Klahr S, Breyer JA, Beck GJ, et al. Dietary protein restriction, blood pressure control, and the progression of polycystic kidney disease. Modification of Diet in Renal Disease Study Group. J Am Soc Nephrol. 1995;5(12):2037-2047.

14. Choukroun G, Itakura Y, Albouze G, et al. Factors influencing progression of renal failure in autosomal dominant polycystic kidney disease. J Am Soc Nephrol. 1995;6(6):1634-1642.

15. Banerjee T, Liu Y, Crews DC. Dietary Patterns and CKD Progression. Blood Purif. 2016;41(1-3):117-122. doi:10.1159/000441072

16. Noori N, Sims JJ, Kopple JD, et al. Organic and inorganic dietary phosphorus and its management in chronic kidney disease. Iran J Kidney Dis. 2010;4(2):89-100.

17. Helal I, Reed B, Mettler P, et al. Prevalence of Cardiovascular Events in Patients with Autosomal Dominant Polycystic Kidney Disease. Am J Nephrol. 2012;36(4):362-370. doi:10.1159/000343281

18. Rahman E, Niaz FA, Al-Suwaida A, et al. Analysis of causes of mortality in patients with autosomal dominant polycystic kidney disease: a single center study. Saudi J Kidney Dis Transplant Off Publ Saudi Cent Organ Transplant Saudi Arab. 2009;20(5):806-810.

19. The American Heart Association Diet and Lifestyle Recommendations. www.heart.org. Accessed November 25, 2019. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/nutrition-basics/aha-diet-and-lifestyle-recommendations

20. Torres JA, Kruger SL, Broderick C, et al. Ketosis Ameliorates Renal Cyst Growth in Polycystic Kidney Disease. Cell Metab. 2019;30(6):1007-1023. doi:10.1016/j.cmet.2019.09.012

21. Banerjee T, Crews DC, Wesson DE, et al. High Dietary Acid Load Predicts ESRD among Adults with CKD. J Am Soc Nephrol. 2015;26(7):1693. doi:10.1681/ASN.2014040332

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