Evidence Poor for Restricting High-Potassium Foods
A plant-based diet might one day prove to be an option for kidney disease patients.
Weak evidence at best supports the advice to avoid plant foods rich in potassium to prevent hyperkalemia in hemodialysis (HD) patients, according to the authors of a new review in the Journal of Renal Nutrition (published online ahead of print).
David E. St. Jules, RD, PhD, David S. Goldfarb, MD, and Mary Ann Sevick, ScD, RN, suggested that multiple, complex factors can alter the effects of food on serum potassium levels in HD patients.
Potassium distribution and excretion
Experimental studies of potassium kinetics show that serum potassium is affected by nervous and endocrine signals, chemical concentrations in and out of cells, circadian rhythms, and organ system functionality. For example, some evidence links acidosis to hyperkalemia in kidney disease patients. Intracellular and extracellular shifts in potassium occur in response to acid-base changes. Insulin also plays a role.
Furthermore, inadequate potassium excretion may contribute to hyperkalemia. When excess potassium is not removed by kidneys, it may be excreted through the bowel. Constipation, a common problem among patients, would hinder excretion.
Dietary and serum potassium
Healthcare providers commonly advise limiting potassium intake to 2000 to 3000 mg per day, especially from nuts, beans, fruits, and vegetables that supply more than 200 mg per portion. Yet a 2010 study by Nazanin Noori, MD, PhD, and colleagues published in the American Journal of Kidney Diseases (2010;56:338-347) found that dietary potassium explained no more than 2% of the variance in quarterly mean predialysis levels of serum potassium. When Dr St. Jules and colleagues examined data from the BalanceWise study, they also found no correlation.
Nutritional characteristics of plant foods
Plant foods high in potassium have been the target of dietary interventions to prevent hyperkalemia. But muscle-based meat products may contain far greater concentrations of potassium, especially when they contain potassium-containing food additives. In addition, some plant foods high in potassium, such as sesame seeds, have low phosphorus bioavailability. Plant foods also have favorable alkalinizing and insulin-stimulating properties that may work to prevent abnormal increases in serum potassium.
More research needed
Telling patients to restrict high-potassium plant foods, such as bananas, kiwis, baked potatoes, tomatoes, and oranges, from their diet is based more on historical practice than empirical research, the researchers stated. Other important factors unrelated to diet may cause hyperkalemia and should be considered, such as prolonged fasting, hyperosmolality, metabolic acidosis, tissue breakdown, constipation, and medications. Dialysis modality and prescription are yet another influential variable.
“Ultimately, we conclude that this approach is not evidence-based and may actually present harm to patients,” Dr St. Jules and colleagues concluded. “However, given the uncertainty arising from the paucity of conclusive data, we agree that until the appropriate intervention studies are conducted, practitioners should continue to advise restriction of high-potassium foods.”
In an accompanying editorial, Katrina L. Campbell, PhD, RD, and Juan Jesus Carrero, Pharm, PhD, agreed. “Although an exciting working hypothesis,” they wrote, “there is however much to be understood before changing clinical practice. As St-Jules et al. argue, we need to provide real evidence on the risks or benefits of this practice and not only assume old traditions.”
1. St. Jules DE, Goldfarb DS, and Sevick MA. Nutrient Non-equivalence: Does Restricting High-Potassium Plant Foods Help to Prevent Hyperkalemia in Hemodialysis Patients? J Ren Nutr. 2016 Sep;26(5):e31-3. doi: 10.1053/j.jrn.2016.02.005.
2. Campbell KL and Carrero JJ. Diet for the Management of Patients With Chronic Kidney Disease; It Is Not the Quantity, but the Quality That Matters. ? J Ren Nutr. 2016 Sep;26(5):e31-3. doi: 10.1053/j.jrn.2016.07.004.