Modified low-phosphorous diet may safely broaden food options for patients on dialysis
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Study results showed patients on hemodialysis who received a modified low-phosphorous diet had similar phosphate levels as those receiving the standard diet, with the modified diet widening patients’ food choice and increasing fiber intake.
According to Fiona Byrne, PhD, of the department of nutrition and dietetics at Cork University Hospital in Ireland, and colleagues, the traditional attempt to control hyperphosphatemia in this patient population is to limit total dietary phosphorous intake; this is often done by moderating protein intake, restricting foods with high phosphorous content (eg, dairy, whole grains, pulses and nuts) and avoiding foods with phosphate additives.
However, the researchers wrote, “[e]merging opinion supports the introduction of more plant protein in the form of whole grains, pulses and nuts where the phosphorus is largely bound by phytate and therefore not as available for absorption ... As there is a strong linear relationship between dietary protein and phosphorus intakes, prescription of protein is essential. This is both to ensure increased protein needs are met, but also to avoid over-consumption of protein which carries an obligatory phosphorus load. It should be possible to ensure adequate protein intake whilst restricting phosphorus.”
To test this “emerging evidence,” the researchers randomized 74 patients to either the standard low-phosphorus diet or a modified one. Key changes in the modified diet included replacing animal proteins with plant proteins (eg, replacing meat with pulses), adding whole grains and cereals, encouraging consumption of more fish and restricting dairy consumption. In addition, while guidelines recommend avoidance of all additives, the modified diet suggested only checking for foods with phosphate E numbers.
“This modified diet introduced pulses, peas and nuts and relaxed restrictions on whole grains,” the researchers elaborated, stressing the health benefits of pulses, the kidney-protective effect of plant-based diets and the notion that liberalizing diets may improve the lives of patients with kidney disease.
For 12 months, the researchers observed no significant difference in the change of serum phosphate between the two groups.
Further findings indicated that while total dietary phosphorus intake was similar between groups, phytate bound phosphorus — commonly found in pulses, nuts and whole grains — was significantly higher in the modified diet group.
Other benefits of the modified diet included higher dietary fiber intake and an increase in bowel movements.
The researchers noted no significant differences in the change in serum potassium or in reported protein intake between the two diets, and both were similarly well tolerated.
Based on the findings, Byrne and colleagues contended the standard renal diet should more closely align with the Mediterranean diet, though nutrient recommendations should always be tailored to the individual patient. They also emphasized the results be interpreted “cautiously” for patients with hyperkalemia.
“While this advice may need to be used more cautiously in hyperkalemic patients, our study in a dialysis population, provides an important first step toward safely reducing restrictions and exploring the effect of a specific dietary pattern on biochemical parameters and tolerance,” the researchers concluded. “The current study shows the feasibility of conducting a large scale, longer duration trial to demonstrate the efficacy of dietary intervention.”
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