Is serum phosphate a useful target in patients with chronic kidney disease and what is the role for dietary phosphate restriction?

Abstract

A complex system of endocrine and paracrine signals exists to control phosphate balance. Dysregulation of these systems in patients with chronic kidney disease has serious clinical consequences. Whilst observational studies have shown associations between higher serum phosphate levels and poor clinical outcomes, the direction of causality has not been demonstrated. Whether there is a target level of serum phosphate remains controversial and no randomized trials to date have proved that strategies to lower extracellular phosphate actually improve clinical outcomes. Serum phosphate provides only a partial measure of overall phosphate balance and, importantly, calcification risk. Changes in dietary phosphate may be a modifiable source of phosphate in humans, although better methods for assessment of dietary phosphate intake are required. Individuals consume large amounts of phosphate in processed foods, rich in phosphate additives, and there is interest in restricting dietary phosphate as a matter of public health, although the association between dietary phosphate and serum phosphate is modest at best. Interventional studies are needed to provide supportive evidence of any potential advantages of dietary phosphate restriction before such measures can be recommended.