Dietary phosphate assessment in dialysis patients

Malnutrition is known to be highly prevalent in patients with kidney disease. It is associated with poor clinical prognosis and can result from restricted dietary protein-energy intake. The issue is also compounded by protein wasting that occurs in dialysis patients. In countering malnutrition, an adequate protein intake is essential but limited by its phosphate content. Therefore, an accurate assessment of nutritional status and intake is an important part of the therapeutic strategy for patients on dialysis. Assessing dietary phosphate intake is not straight forward, with many confounding factors requiring consideration. Interview and diet diaries are the preferred means by which dietary intake can be estimated. However, it is evident that these estimates can vary considerably and are subject to underreporting. Moreover, the use of phosphates as additives and their omission from available nutrient databases are significant contributors to this variation and underestimation. This review highlights the main limitations in assessing dietary phosphate intake and introduces the concept of monitoring changes in dietary habit (appetite) as a proxy for dietary protein and energy intake. This review discusses the use of monitoring dietary habit in trials, with phosphate binders as a simple tool to address the possibility that changes to dietary habits may influence phosphate binder efficacy.