Intensive dietary interventions may further decrease serum phosphate concentrations in peritoneal dialysis (PD) patients compared with phosphate binder therapy alone, a small study suggests.
For the trial, Jiaqi Qian, MD, of Ren Ji Hospital, in Shanghai, China, and colleagues tracked serum phosphate levels in 97 PD patients over the course of a year. All patients took a calcium carbonate phosphate binder; half also reduced their dietary intake of phosphate under the guidance of a dietitian and PD nurse.
According to results published online ahead of print in Nutrition, Metabolism and Cardiovascular Diseases, serum phosphate concentration declined significantly in the dietary intervention group from 1.98 to 1.65 mmol/L, as intake of dietary phosphate also declined. Furthermore, fewer patients on a low phosphorus diet needed to use a phosphate binder while others reduced their dose. By comparison, serum phosphate concentration remained stable in the control group who took phosphate binders alone.
The researchers, who observed that limiting dietary phosphate is notably challenging for patients, analyzed subgroups based on patient compliance to the interventions: 1 group limited phosphorus-rich foods, another changed to phosphorus-reducing cooking methods (e.g., boiling, stewing, and pre-soaking meat for an hour), and yet another group did both. Family members were asked to support the changes. Dietary phosphate decreased significantly in all 3 groups, but especially in the group that altered both their diet and cooking.
“The two dietary intervention components in our study, lowering phosphate rich food or changing cooking method, showed independent effect on reducing phosphate intake in PD patients,” the investigators wrote. Modifying cooking methods did not decrease serum phosphate concentration significantly, however. The researchers suggest reducing phosphate-rich foods may be more important.
To lower their dietary phosphate, patients were asked to reduce phosphate-rich foods, such as meat and dairy items and foods with a high phosphate-to-protein ratio, such as soft drinks, fast food, processed foods, and condiments and other products containing phosphate-salt additives. Patients completed a 3-day diet diary twice a month and provided it to the dietitian and PD nurse during their monthly sessions. Patients recorded the weight of raw foods and how food was cooked. For processed foods, they also provided the nutrition label. The researchers used a software program to estimate dietary phosphate and other nutrients based on the diaries, which they noted may underestimate phosphate intake by 250 mg/day (compared with chemical analysis).