From bland to beneficial, Purdue nutrition science researcher explores diet as a tool for kidney disease prevention

Written By: Rebecca Hoffa, rhoffa@purdue.edu

Pasta without sauce. Unsalted crackers. Plain white rice. What is traditionally known to be the renal diet — a complicated diet with a wide range of restrictions, including limited protein, potassium, phosphorus and sodium — often lacks flavor and color, leaving individuals with chronic kidney disease (CKD) who have been prescribed the diet dissatisfied with their meal options. Some patients go as far as ignoring aspects of the diet altogether.

Brandon Kistler, assistant professor in Purdue University’s Department of Nutrition Science, and his lab group are interested in delving deeper into the evidence behind the traditional renal diet, seeking to uncover how individuals can better manage CKD and even prevent kidney failure before it occurs.

Brandon Kistler

“(The renal diet) is this complex diet with unique advice that is really difficult to follow, and so I started to get into, ‘Why do we tell people to do this?’” Kistler said. “We were telling people with CKD the opposite of what we were telling the general population, and I was curious as to what the evidence was for that, and I found out that there really wasn’t as much evidence as we would like to support what we were doing.”

Kistler was recently awarded a K12 career development award from the Indiana Clinical and Translational Sciences Institute expand on his work that aims to improve the lives of those with CKD. His research, which will involve a controlled feeding trial, will focus on the connection between the gut microbiome, the kidneys and their role in cardiovascular and muscle health.

“A lot of people with CKD don’t actually die from kidney disease — they die from cardiovascular disease,” Kistler said. “Particularly in younger adults, cardiovascular disease is 20 times more prevalent in people with CKD than in the general population. In the CKD population as a whole, it’s a little more moderated, but it’s still much higher risk.”

Kistler noted the kidneys serve to remove unused substances created during metabolism. When the kidneys aren’t functioning, they don’t remove those byproducts — also known as uremic toxins — that can be harmful to the body. Because some of these toxins are generated in the gut microbiome, Kistler and his research team are interested in understanding the connection between the gut, the kidneys, and how that goes on to affect the heart and other muscles. Through this work, he hopes to gain insights into the most effective dietary recommendations for this population.

“Essentially we’re looking at: If we manipulate aspects of the diet, can we alter the production of these gut-derived toxins so that we lower them and — to a certain extent — offset the fact that there’s less removal of these toxins by the kidney?” Kistler said.

Beyond the complexities of the renal diet, patients with CKD also often face challenges in getting the support and care they need due to limited access to dietitians as a source for prevention before they experience kidney failure. Kistler, who serves as associate councilor of the International Society of Renal Nutrition and Metabolism (ISRNM), recently published an editorial alongside fellow ISRNM collaborators addressing this issue and discussing the need for greater clinical support, particularly in developing nations.

“One of the major points that we tried to make in that editorial is the importance of expanding access to dietitians,” Kistler said.

As Kistler’s research has evolved over the course of his career, ultimately leading him to the College of Health and Human Sciences, he commented that his focus on CKD has continued to move in the same direction as the nutrition field as a whole, working toward personalized nutrition rather than sweeping recommendations.

“We’ve moved to trying to be more individualized rather than coming up with interventions that would work across everyone,” Kistler said. “We’ve become much more detailed, looking in-depth at trying to understand the microbiome, the metabolome and how all of these metabolic intermediates might help play into an optimal path for an individual person.”

However, CKD has historically been under-researched, so Kistler is also looking ahead to all the unknowns left to explore. Ultimately, Kistler’s goal is to simplify renal nutrition for individuals with CKD and help them have the resources they need to make healthy decisions.

“The difference between kidney disease and some other conditions, such as diabetes, is that there’s been much less research in CKD, so there’s a lot of big questions that remain unanswered,” Kistler said.