April 2025 Issue
Rethinking Polycystic Kidney Disease
By Alexandria Hardy, RDN, LDN
Today’s Dietitian
Vol. 27 No. 4 P. 28
Can Nutrition Be a Game Changer?
Polycystic kidney disease (PKD) is one of the most common genetic disorders in the United States, where it affects over half a million people.1 While age, race, and ethnicity are not predictive factors, men with PKD may be more likely to experience a higher severity of disease; this could be due to hormonal differences.2
There are two main types of PKD. The first type, autosomal dominant PKD (ADPKD), is more common and manifests in adulthood.1 The second type is called autosomal recessive PKD and is typically diagnosed during gestation or in the first few years of life.1,2 The focus of this article will be ADPKD.
PKD is characterized by fluid filled cysts that grow in the kidneys, particularly around the nephrons and ducts.2 These cysts distort and enlarge the natural shape of the kidney as they can grow up to 5 cm in diameter. These cysts may or may not be painful and can cause complications like CVD, hypertension, and kidney failure if left untreated. Both types of PKD can lead to chronic kidney disease (CKD), which is characterized by a progressive loss of kidney function, and end-stage renal disease (ESRD), which requires dialysis or a kidney transplant for the health and survival of the patient.2
The Basics of PKD and Its Genetic Component
As PKD is a hereditary disease, much research has been devoted to understanding the epidemiological effects. Over three-quarters of ADPKD cases can be attributed to mutations in the PKD1 gene, and the remaining 25% are associated with either PKD2 mutations, rare mutations, or unknown genetic factors.2 PKD1 mutations can lead to a decrease in glomerular filtration rate, an increased kidney volume, and premature initiation of ESRD.2
Many patients with ADPKD can develop ESRD in their 50s or 60s, depending upon their functional renal volume. Offering screening for asymptomatic family members may be a helpful metric to provide early diagnosis and lifestyle intervention.3,4 Lifestyle interventions can include adapting specific eating patterns, physical activity, stress management, and sleep hygiene to optimize kidney function.
This article will aim to better understand the impact of lifestyle interventions, particularly nutrition, on PKD and explore the question: are our genetics our destiny, or can diet and lifestyle mitigate the risk?
New Frontiers in Nutrition Therapy
Traditional nutrition therapy approaches to treating kidney disease include managing minerals like sodium, potassium, phosphorous, and others; regulating fluid intake; controlling protein amount and type; and addressing dietary acid load. Current research is focused on exploring the impact that specific dietary approaches like the keto diet and a plant-based dietary pattern may have, as well as investigating the role of timing protein intake.
Time Restricted Feeding and the Ketogenic Diet
A 2024 review published in Nutrients advocates for the elimination of the Standard American Diet (SAD) and encourages implementation of the ketogenic diet for individuals with kidney disease.4 The review scrutinizes foods/food groups that may exacerbate PKD symptoms, like an overconsumption of carbohydrates that may lead to hyperglycemia.4
In animal studies, ketogenic metabolic therapy (defined here as carbohydrate intake of 20 to 50g/day, moderate protein intake, and the remaining calories coming from fat) combined with time restricted feeding has shown a slower disease progression.4
Clinical trials have shown similar positive results, though sample sizes were small (24 to 131 patients) and the trials short (three to six months).4-7 Melanie Betz, MS, RD, CSR, LDN, FNKF, FAND, founder and CEO of The Kidney Dietitian, cites concern over the oversight provided in the trial compared with real world support. “The human trials include a massive amount of dietitian support that is simply not feasible in the current health care system,” says Betz. She also mentions that the standard in these studies is often SAD, stating, “There is no research comparing these highly restrictive strategies (like ketogenic metabolic therapy) to the typical renal nutrition strategies such as reduced sodium, protein, dietary acid load, etc. All research compares them to the Standard American Diet, which is known to be harmful for kidneys.”
Jessianna Saville, MS, RDN, LD, CLT, and RISE Nutrition for PKD founder and program dietitian, concurs, highlighting that “critical research gaps exist in understanding how ketogenic diets affect different patient populations and how individual nutrigenomic profiles influence PKD progression.”
Plant-Based Diets
Candace Mooney, MS, RDN, CSR, owner of Nourished Pear, is “100% behind plant-focused diets for reducing kidney strain for PKD patients. This helps ensure they are eating more negative PRAL [potential renal acid load] foods and also giving them a diet high in vitamins, minerals, and antioxidants.” She typically introduces this concept by recommending recipes that are plant-forward as well as encouraging patients to meet their fruit and vegetable recommendations, which also boosts their fiber intake. Though small studies have shown that a plant-forward diet may improve or protect kidney function, more data is needed to determine causation before establishing vegetarian or vegan diets as a gold standard for renal care.8-10 A review published in Frontiers in Medicine found that there was no clear answer on whether different protein sources affect the risk of CKD progression (regardless of protein quality), which is data that may be extrapolated to PKD as well.8
Impact of Protein Intake and Timing
There is mixed evidence that low-protein diets may be impactful for individuals with PKD.11 There are no current dietary guidelines specific to PKD, and most clinicians use nondialysis CKD or 2020 Kidney Disease Outcomes Quality Initiative (KDOQI) recommendations.8 A review in Clinical Nutrition Open Science affirms that while low-protein diets may slow the progression of disease in animals, more data from human clinical trials is needed, particularly on the impact of plant protein.11 Ideally, protein intake should be spread throughout the day in small, regular portions based on ideal protein intake calculated by a renal dietitian. It’s also important to make sure that individuals who are consuming a protein-restricted diet are taking in adequate calories from nutrient dense sources to promote overall health and well-being.
Both Betz and Amy Harshman, RD, LD, CMBEC, a program dietitian from RISE Nutrition for PKD, calculate protein intake for their patients using rates between 0.55 to 1.3g/kg/day depending on factors like serum creatinine and blood urea nitrogen trends, PRAL of dietary intake, proteinuria, comorbidities, activity level, and overall nutrition status.
Harshman strongly encourages staying within these guidelines from the KDOQI because “going below 0.6g/kg/day risks malnutrition, while exceeding 1.3g/kg/day may accelerate disease progression.” This idea was supported in a systematic review and meta-analysis published in the Journal of Cachexia, Sarcopenia, and Muscle, studying the impact of low-protein diets on CKD. They determined that diets that limited daily protein intake to <0.8 g/kg/day were more likely to yield higher serum bicarbonate levels and lower levels of phosphorus, azotemia, all-cause mortality, and progression to ESRD.12 Further limiting intake to <0.4 g/kg/day improved kidney function and delayed ESRD even more, but such a reduction is difficult to adhere to for many individuals and may have other negative consequences, like malnutrition, if followed for years.12
Lifestyle Interventions Beyond Diet
While nutrition plays a large role in kidney health and function for PKD patients, there are other functional approaches that are important to discuss with patients. These interventions include physical activity, stress management, and sleep hygiene practices and can be implemented by both symptomatic and asymptomatic individuals.
Physical Activity
A review published in Nutrients supports the KDIGO 2021 guidelines for CKD, which encourage at least 150 minutes per week of physical activity.13 The biggest benefits for individuals with PKD are maintenance of their functional movements and activities of daily living, as well as a decrease in mortality risk.13 Regular engagement in physical activity may also improve comorbidities like CVD. More research is needed to determine the most effective types and intensity of exercise, as current recommendations only caution against contact sports (due to potential cyst ruptures) vs providing a gold standard.13
Psychosocial Stress Management
Betz encourages patients to make psychosocial stress management an integral part of their kidney health management, highlighting the link between mental and physical health. “For PKD, blood pressure is key as high blood pressure and vasopressin contribute both to a decline of kidney function and cyst growth. Stress is clearly linked with high blood pressure. So, stress reduction and management is key for PKD and general kidney health! Enlisting the health of a therapist can be life changing to help manage stress for anyone, and especially someone managing a chronic illness,” Betz says. This could be an excellent opportunity for RDs in private practice to forge relationships with local therapists, cultivating potential referral sources and improving overall coordination of care.
Sleep and Circadian Rhythms
Sleep quality, as it supports internal circadian rhythms, can have a significant impact on kidney function. In a paper published in the Journal of Clinical Investigation, researchers found that CKD (and decreasing kidney function in particular) was linked to poor sleep.14 Specifically, the later an individual went to bed, the less they slept, and the more their sleep was disrupted, the worse their renal function was likely to be.14 The researchers
theorized that this may be due to a bidirectional or cyclical relationship. 14
Therapeutic treatments for circadian rhythms that are specific to ESRD include nocturnal dialysis (preferably at home) to help restore circadian rhythms. More research is needed to determine how circadian disruption affects physiological functioning, but dietitians can promote positive sleep hygiene in a variety of ways, such as addressing nutrition factors impacting sleep, encouraging regular sleep and wake times, and helping patients build a wind-down routine and healthy
sleep environment.
Patient Empowerment
For patients newly diagnosed with PKD, it can be a challenge to know where to begin finding information about managing their condition with the aid of diet and lifestyle interventions. Kelly Welsh, RDN, CD, RISE Nutrition for PKD program coordinator, encourages her clients to prioritize nutrition early on by working with a dietitian who is a PKD expert who can personalize a plan that suits their specific needs, labs, and lifestyle. She will often use positive reinforcement to remind her clients that “managing PKD is a journey, not a sprint, and by combining early nutrition, personalized guidance, and education about your labs, you’ll be well-equipped to make meaningful, positive changes that support your kidney health and overall well-being.”
Challenges and Gaps in Research
Betz views one of the biggest challenges historically facing patients with PKD and clinicians is the “sit and wait without much active intervention to help slow the disease process, especially from a diet perspective.” She is beginning to see this change as nutrition research in the field grows. Mooney reports that she is beginning to see a proactive approach emerge with her clients, where many are advocating for themselves and taking a leadership role in their care.
Other clinicians may not know how or when to involve the RD in renal care. Saville notes that “comprehensive research on dietary interventions would help the nephrology community confidently integrate nutrition and lifestyle modifications as core treatments rather than supplementary measures.” She encourages health care providers like RDs to stay up to date with research and to provide specific and meaningful dietary advice to create “momentum for sustained lifestyle improvements.” Betz concurs, advocating for RDs to provide education to other clinicians to promote consistent, science-based messaging about the value they provide to their patients as well as the role nutrition plays in managing PKD.
Conclusion
Though PKD can seem like an overwhelming and discouraging diagnosis, recent research affirms that lifestyle interventions like nutrition may impact the speed of its progression. Updated standardized clinical guidance regarding nutrition is needed as large, well-designed clinical trials yield new data. As one of the first lines of lifestyle intervention, RDs are in a position to help patients form personalized, sustainable, and impactful nutrition, exercise, and sleep habits that can slow PKD progression while allowing them to live a fulfilled life.
— Alexandria Hardy, RDN, LDN, is a writer and the owner of Pennsylvania Nutrition Services, an insurance-based private practice located in Lancaster, Pennsylvania.
References
1. What is polycystic kidney disease? National Institute of Diabetes and Digestive and Kidney Diseases website. https://www.niddk.nih.gov/health-information/kidney-disease/polycystic-kidney-disease/what-is-pkd. Updated January 2017. Accessed January 8, 2025.
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