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How plant-based diets can benefit patients with NND-CKD
by Sara Colman Carlson, RD, CDE
Today’s kidney diet is healthier than the refined and restrictive diet patients were instructed to follow 10 years ago. Legumes, whole grains, nuts, seeds, fresh produce and Greek yogurt are among some of the foods dietitians now counsel their patients to include, albeit there’s still caution around the amount and frequency. Dietitians are embracing whole, minimally processed foods and focusing on healthy meals instead of the individual mineral content of foods.
The Dietitian’s Pocket Guide to Nutrition Assessment of the Patient with Kidney Disease notes, “Do not restrict the diet above what is necessary to maintain adequate clinical, nutrition and metabolic status. Dietary recommendations should be presented as goals rather than restrictions and individualized to the patient.”
Yet there is still apprehension around loosening up certain diet restrictions for fear of potassium and phosphorus levels taking a negative turn in response to a plant-based diet. Only after working with patients, monitoring the impact of intake changes and seeing a positive result, do dietitians have the assurance a healthier, liberalized renal diet is possible. We’re hungry for more studies on the effects plant-based diets have on lab results and health of both patients with non-dialysis-dependent CKD (NDD-CKD) and patients on dialysis.
I interviewed Deborah Clegg, PhD, a kidney disease researcher, clinical dietitian and a member of the Distinguished Science in Residence, Health Studies program at American University, Washington, DC. She is the author of the article, “Plant-based diets and CKD,” which was recently published in the Clinical Journal of the American Society of Nephrology. We discussed the risks and benefits of a plant-based diet for patients with NND-CKD.
Sara Colman Carlson, RD, CDE: What are the benefits of a plant-based diet for those diagnosed with NND-CKD?
Deborah Clegg, PhD: Eating diets high in potassium have incredible benefits for people who have normal functioning kidneys. Diets high in potassium decrease blood pressure, decrease the risk of stroke, enhance nerve function and protect your kidneys. However, as kidneys fail you can no longer have normal potassium balance and that can lead to hyperkalemia. Having normal potassium homeostasis is critical, and the kidneys are the critical organ within our body that maintains that homeostasis.
Colman Carlson: There’s a wide range of potassium allowance in NDD-CKD based on how much the kidneys can remove. Who is at the highest risk for having hyperkalemia related to higher potassium intake in their diet?
Clegg: This is an area that is garnering some much-needed research. Those individuals who have a reduction in kidney function might be those same individuals who have high blood pressure or have diabetes or abnormal blood glucose, or cardiovascular disease. If you have hypertension, diabetes or cardiovascular disease and your doctor has told you that your kidneys are having a decrease in overall function, you would be an individual who we would want to most monitor your diet, specifically with respect to how much potassium you are taking in.
Preventing hyperkalemia while liberalizing the renal diet is top of mind for practitioners. Clegg discussed the newer medications that may help balance potassium levels by binding it in the gut.
Colman Carlson: What can we tell patients with NDD-CKD who are trying to increase the amount of plant foods in their diet but are on the borderline of having high or normal potassium levels?
Clegg: There are some newer products available on the market that may allow people with CKD to be able to incorporate fresh fruits and vegetables in their diet or a more plant-based diet to provide them some of the health benefits associated with those foods. We’re encouraging individuals who have been diagnosed with NDD-CKD to talk to their doctor to see if they might be eligible for trying some of these newer products. Every individual is different, but there may be certain individuals who can enjoy the benefits of fresh fruits and vegetables in their diet if they are being monitored carefully with their physicians.
Colman Carlson: It sounds like these medications are similar to a phosphorus binder. Is that the way they work?
Clegg: Your analogy is right. These binders are similar to phosphate binders and in some cases, the binders might be beneficial for phosphorus as well. When you take a diet that’s enriched with potassium, these binders bind to the potassium and allow for excretion. They take over the function of the kidney and help to keep potassium levels low.
Physicians are becoming educated on these newer products and might allow for some diet liberalization that includes fresh fruits and vegetables while taking the binders.
Colman Carlson: Who can take these medications?
Clegg: The research has been done with patients who are on dialysis; smaller studies have been done with people with NND-CKD. The excitement is that it will allow people to have a healthier diet while being on these binders and have the benefits of being able to eat foods that their family members are eating at the same time and enjoy some of those benefits.
Colman Carlson: Many patients in stage 3 and 4 CKD may be more liberal with fruits, vegetables, whole grains, nuts and legumes. Do those foods increase their potassium levels much when their kidneys are still getting rid of some potassium?
Clegg: There has been a large call for additional research trying to understand if there is a sweet spot with respect to kidney function and the ability of the kidney to buffer the potassium levels. We need to go back and peel it like an onion — begin to understand where the potassium is in the diet, what types of foods contain the potassium, how it influences kidney function and then what the role of these binders might be in enabling people to sort of have their cake and eat it, too.
We also are beginning to wonder if all food sources that contain potassium cause the same level of increase in blood potassium.
Our discussion also focused on gastrointestinal health and the interest in additional research in this area.
Colman Carlson: One of the benefits of being able to include more plant-based foods is the fiber. We’re seeing more studies on the benefits of fiber regarding gut health and cardiovascular disease. Patients with NDD-CKD who are restricting plant-based foods have more problems with constipation and bowel issues. From personal observation, it seems that having the increased fiber may help with potassium control. Is this due to removal of potassium through the GI tract?
Clegg: What’s exciting is we are beginning to realize that the gastrointestinal tract can maintain potassium homeostasis. So, as we incorporate fresh fruits and vegetables which are higher in fiber, we then begin to allow the GI tract to help us with potassium homeostasis. These binders also work within the GI tract. More information about the good old gut and how it functions with respect to potassium balance is going to be something important.
References:
McCann L, et al. National Kidney Foundation. 2015; 5th Edition.
Clegg D, et al. Clin J Am Soc Nephrol 2019; doi.org/10.2215/CJN.08960718
Packham D, et al. N Engl J Med 2015;doi:10.1056/NEJMoa1411487.
Rodrigues Neto Angéloco, et al. J Ren Nutr. 2018;28:215-220.
St-Jules DE, et al. J Ren Nutr. 2016;26;282-287.
Weir D, et al. N Engl J Med 2015;doi:10.1056/NEJMoa1410853.
Sara Colman Carlson, RD, CDE, is the DaVita.com nutrition manager. She has worked in nephrology for more than 28 years.
Disclosures: Colman Carlson reports no relevant financial disclosures. Some of Clegg’s research has been supported by Relypsa Inc.
Editor’s note: On May 6, 2019, Dr. Clegg’s affiliation was changed to her current affiliation. Healio/Nephrology regrets the error.