Researchers at New York University School of Medicine question the practice of advising hemodialysis (HD) patients to restrict intake of high-potassium plant foods to prevent hyperkalemia, according to a recent review.

In a paper published online ahead of print in the Journal of Renal Nutrition, David E. St-Jules, RD, PhD, and colleagues concluded that evidence linking high dietary potassium intake to hyperkalemia in HD patients is “virtually non-existent.”

“In the absence of empirical evidence, it is of course prudent to continue to recommend low-potassium diets to HD patients with hyperkalemia; however, the practice of advising patients to eliminate so many plant foods from the diet may be harmful, and must be evaluated.”

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The authors noted that patients with end-stage renal disease (ESRD) treated with intermittent HD are advised to follow a low-potassium diet (2,000–3,000 mg/day), which involves avoiding high-potassium, plant-based foods, such as seeds, nuts, beans, and peas, as well as many commonly consumed fruits and vegetables.

Targeting of high-potassium foods is based on the assumption that all dietary potassium is therapeutically equivalent, the team noted. “Dietary potassium is not alone in being regarded this way,” the authors wrote. “HD patients with hyperphosphatemia are advised to avoid many high-phosphorus foods that may contribute minimally to hyperphosphatemia due to their relatively low phosphorus bioavailability.”

Dr. St-Jules’ group cited prior research demonstrating that potassium excretion in stool was 3 times higher in HD patients compared with normal controls. “Fecal potassium content was directly proportional to dietary potassium intake and stool weight.” The increase in bowel potassium excretion in patients with chronic kidney disease was later shown to be primarily the result of potassium secretion into the bowel rather than reduction of small intestine absorption of dietary potassium. “Given the relatively high prevalence of constipation in HD patients, infrequent bowel movements may be an important determinant of hyperkalemia in HD patients.”

“In addition to impairing nutrition status and quality of life,” they wrote, “advising HD patients to limit or avoid many plant-based  foods, especially fruits and vegetables, may contribute to adverse metabolic status, such as oxidative stress, inflammation, metabolic acidosis, dyslipidemias, and conditions that negatively impact HD patient health, such as constipation and hypertension.”

The authors pointed out that other nutrients in food influence potassium distribution and excretion. Unlike meat, which when metabolized leads to net acid production and which are low in carbohydrates and contain no fiber, plant foods, especially fruits and vegetables, tend to yield net base production and are high in both carbohydrates and fiber. They researchers noted, for example, that although the pH of oranges is acidic, the net result of orange juice ingestion is urinary alkalinization. “Therefore, compared with high-potassium meat, potassium-rich plant foods may promote distribution of a greater proportion of dietary potassium intracellularly (alkaline and insulin-stimulating) and excretion of potassium in stool by increasing fecal bulk (dietary fiber).”