It’s one of the biggest conundrums nephrologists face – how to prevent or treat chronic hyperkalemia by managing diet in patients with chronic kidney disease.
Hyperkalemia is the medical term that describes potassium levels in a patient’s blood that are higher than normal. Hence, the traditional recommendation for managing these with patients is to keep them off foods high in potassium.
The problem, as pointed out by Kamyar Kalantar-Zadeh, MD, MPH, PhD, chief of nephrology, hypertension, and kidney transplantation at the University of California Irvine School of Medicine, is that potassium is critical to the normal functioning of cells, and ensures the proper functioning of nerves and muscles, including the heart. “So potassium is extremely important,” he told MedPage Today, “And it has been shown to lower blood pressure, lower the risk of stroke and heart disease, and increase longevity.”
According to the National Kidney Foundation, a normal amount of potassium in the typical healthy American’s diet is 3,500 to 4,500 mg per day, while a potassium-restricted diet will usually be 2,000 mg per day. Foods that are high in potassium and likely to be targeted for restriction include many fruits and vegetables including such mainstays as bananas, avocados, and oranges.
“Everything that is healthy has potassium in it,” said Kalantar-Zadeh. “It is the quintessential component of fresh fruit and vegetables.”
Heart-healthy diets are therefore loaded with potassium, he continued. “So it is heartbreaking to have to tell a patient, or hear my dietitian tell patients, that they have to eliminate or limit foods like bananas, or avocados, or fruits and nuts – all of those things that are heart healthy.”
So, restricting diet can present patients and caregivers with therapeutic tradeoffs and associated challenges.
For example, a recent article in Kidney Medicine noted that low-potassium diets can adversely affect patients’ acid-base balance and intestinal microbiota, and result in nutritional deficiencies that reduce health-related quality of life.
The authors also wrote that patient adherence to these dietary restrictions can be problematic since it requires individualized dietary regimens and access to skilled dietitians and regular counseling – something that may not be too common in regular clinical practice. Furthermore, the article stated, there are a number of patient-reported barriers to adherence that are associated with diet restriction, including “a lack of appetite, craving salty foods, being too tired to cook, finding the diet bland and tasteless, difficulty tracking nutrient intake, feeling deprived, and lack of motivation to eat the right foods.”
Kalantar-Zadeh emphasized that while kidney disease has a close relationship with hyperkalemia, in many cases a patient’s condition can be managed before he or she develops chronic hyperkalemia. That does entail a close look at diet, but restriction does not have to mean elimination, he said.
In an article in Nutrients that Kalantar-Zadeh co-authored, he and his colleagues emphasized that careful control of the dietary potassium load is an important aspect of the management of chronic kidney disease and heart failure patients with, or at risk of hyperkalemia.
For example, they wrote, management of patients with stage 4/5 non-dialysis-dependent chronic kidney disease and end-stage renal disease needs “synchronized” dietary potassium with other nutritional goals such as optimal protein intake (reduced in the case of non-dialysis-dependent chronic kidney disease, or increased in end-stage renal disease), fixed acid protection and cardiovascular effects, and an overall heart-healthy mix of foods.
Additionally, cutting back on potassium-rich foods must not lead to decreases in alkali or fiber intake. The latter particularly is important in limiting potassium absorption, by promoting intestinal motility and thus flushing out excess potassium via increases in stool bulk.
Therefore, Kalantar-Zadeh and his colleagues suggested that clinicians should implement interventions such as:
- Knowledge and education about the type of foods which contain excess potassium (per serving or per unit of weight), about the foods needed for proper nutrition in CKD and end stage renal disease, and that supply a low potassium load
- Classification of foods based on their potassium content normalized per unit of fiber
- Education about the use of cooking procedures (especially boiling) in order to achieve demineralization and in particular for removing potassium before eating
They also noted that hidden sources of potassium, such as food additives and low-sodium salt substitutes need to be monitored, as well.
In the Journal of Nutrition, Kelly Picard, RD, BSc, wrote last year that use of potassium additives in processed foods is growing, with amounts that far exceed that which naturally occurs in fresh produce and meat. “Clinicians and patients need to be aware of these changes in the food source to ensure potassium diet teaching is effective and safe,” said Picard.
And since hypertension and proteinuria are well-known complications of chronic kidney disease, many patients will use salt substitutes to flavor their food. A recent review published in Hypertension noted that while replacing regular salt with potassium-enriched salt substitutes can successfully lower blood pressure, it does present risks to patients susceptible to hyperkalemia, such as those with chronic kidney disease.
On the other hand, approval of new potassium-binding agents — sodium zirconium cyclosilicate and patiromer — have been shown to effectively and safely reduce serum potassium levels and could eventually provide clinicians and patients with an alternative (or supplement) to dietary alterations.
“So now we have a number of potassium binders that could help to allow our patients to do better with hyperkalemia surges so that they can enjoy more healthy foods,” said Kalantar-Zadeh.
He added, though, that further research is still needed to demonstrate that these agents can genuinely provide patients with more flexibility to eat fruits and vegetables with high potassium. “We just don’t know yet.”
Kalantar-Zadeh has received commercial honoraria and/or support from Abbott, Abbvie, Alexion, Amgen, AstraZeneca, Aveo, Chugai, DaVita, Fresenius, Genentech, Haymarket Media, Hospira, Kabi, Keryx, Novartis, Pfizer, Relypsa, Resverlogix, Sandoz, Sanofi, Shire, Vifor, UpToDate, and ZS-Pharma.