Effect of food additives on hyperphosphatemia among patients with end-stage renal disease: A randomized controlled trial

Context High dietary phosphorus intake has deleterious consequences for renal patients and is possibly harmful for the general public as well. To prevent hyperphosphatemia, patients with end-stage renal disease limit their intake of foods that are naturally high in phosphorus. However, phosphorus-containing additives are increasingly being added to processed and fast foods. The effect of such additives on serum phosphorus levels is unclear. Objective To determine the effect of limiting the intake of phosphorus- containing food additives on serum phosphorus levels among patients with end-stage renal disease. Design, Setting, and Participants Cluster randomized controlled trial at 14 long-term hemodialysis facilities in northeast Ohio. Two hundred seventy-nine patients with elevated baseline serum phosphorus levels (>5.5 mg/dL) were recruited between May and October 2007. Two shifts at each of 12 large facilities and 1 shift at each of 2 small facilities were randomly assigned to an intervention or control group. Intervention Intervention participants (n=145) received education on avoiding foods with phosphorus additives when purchasing groceries or visiting fast food restaurants. Control participants (n=134) continued to receive usual care. Main Outcome Measure Change in serum phosphorus level after 3 months. Results At baseline, there was no significant difference in serum phosphorus levels between the 2 groups. After 3 months, the decline in serum phosphorus levels was 0.6 mg/dL larger among intervention vs control participants (95% confidence interval, -1.0 to -0.1 mg/dL). Intervention participants also had statistically significant increases in reading ingredient lists (P<.001) and nutrition facts labels (P = .04) but no significant increase in food knowledge scores (P = .13). Conclusion Educating end-stage renal disease patients to avoid phosphorus- containing food additives resulted in modest improvements in hyperphosphatemia. © 2009 American Medical Association. All rights reserved.