Dialysis Patients Struggle to Restrict Dietary Phosphorus

Soda and fast food intake may add to the difficulty of phosphorus control.
Soda and fast food intake may add to the difficulty of phosphorus control.

ISTANBUL—Despite increased awareness of the phosphorus content of food, many patients on dialysis do a poor job of restricting dietary phosphorus intake, according to the results of a survey described at the 50th Congress of the European Renal Association-European Dialysis and Transplant Association.

Elizabeth Lindley, PhD, at Leeds Teaching Hospitals NHS Trust in Leeds, UK, and co-workers analyzed responses to an online questionnaire that examined dietary trends among dialysis patients and the problems associated with phosphorus control.

Forty-eight dietitians, 35 nurses, and one physician responded to the questionnaires. They represented clinics with more than 15,000 dialysis patients. Respondents were from the Netherlands, Spain, Sweden, and the U.K. The survey was organized by the European Dialysis and Transplant Nurses Association/European Renal Care Association, which is the ERA-EDTA's multidisciplinary sister organization. 

Hyperphosphatemia, a common disorder in dialysis patients, is an established risk factor for cardiovascular mortality, said Dr. Lindley, a clinical scientist in renal care. Achieving recommended levels of protein intake while maintaining guideline-recommended levels of serum phosphorus is associated with better outcomes in dialysis patients. Patients on dialysis typically require a combination of dietary modification and phosphate binder therapy (to reduce intestinal absorption of phosphorus) to manage hyperphosphatemia, she added.

Maintaining optimal serum phosphorus levels may be difficult for patients, however. In fact, in the prospective Dialysis Outcomes and Practice Patterns Study (DOPPS), less than half of hemodialysis (HD) patients maintained their serum phosphorus level below the upper limit of the target range of 5.5 mg/dL over the five-year study period.

Dietary counseling has been shown to help patients with chronic kidney disease (CKD) achieve the required reduction in phosphorus burden, she observed.  At the same time, consumption of beverages and fast foods that have a high amount of phosphorus-containing additives makes it more difficult for patients to reach their target serum phosphorus levels.

Dr. Lindley explained that the increasing popularity of processed convenience food has markedly increased the amount of phosphorus consumed by the general population. Phosphorus-containing additives are often added to processed foods to prolong their shelf life and enhance their color or flavor.

Survey results showed that since entering practice a mean of 15 years ago, 47 (56%) respondents had observed an increase in fast food consumption, and 40 (48%) respondents had noticed an increase in consumption of foods rich in phosphorus-containing additives/preservatives. Fifty survey participants, or 60%, believed that there has been a trend of increasing awareness of the phosphorus content of fresh food in CKD patients.

HD patients were reported as being most likely to have difficulty restricting phosphorus. Thirty two (40%) respondents reported that most of their hemodialysis patients found it difficult to follow advice on phosphorus restriction. When asked about the relative importance of restricting phosphorus and maintaining protein intake in HD, 42 (50%) respondents considered them equally important and 30 (36%) favored maintaining protein intake even if maintaining protein intake worsened phosphorus control.

Dr. Lindley urged the “renal community” to lobby for accurate labeling of food and beverages that cites the use of phosphorus additives and specifies phosphorus content per portion. “Thorough and honest labeling would enable patients to avoid or limit their intake of unnecessary phosphorus from additives and help maintain adequate protein intake within the restriction imposed by dialysis and an acceptable phosphate binder regimen,” she said.

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