Prescribed dietary phosphate restriction, as practiced today, is not associated with improved survival among hemodialysis (HD) patients, according to a new study. In fact, it may even increase the risk of death.

The study, led by Steven Brunelli, MD, of Brigham and Women’s Hospital and Harvard Medical School in Boston, and Katherine Lynch, MD of Beth Israel Deaconess Medical Center in Boston, examined data from the HEMO Study, a large-scale, prospective study among dialysis patients in which dietary prescription was recorded. The researchers analyzed data from 1,751 patients on dialysis who were prescribed daily dietary phosphate that was restricted to levels below 870 mg, 871-999 mg, 1,000 mg, 1,001-2,000 mg, and not restricted in 300, 314, 307, 297 and 533 participants, respectively.

Patients who were prescribed more restrictive dietary phosphate levels had poorer nutritional status and were more likely to require nutritional supplements, the study showed.Patients with more liberal dietary phosphate restrictions were less likely to die during the study. Compared with patients whose dietary phosphate prescription was less than 870 mg/day, those prescribed 1,001-2,000 mg/day and subjects with no specified phosphate restriction were 27% and 29% less likely to die, respectively.

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“Our data suggest that prescription of low phosphate diets did not improve survival among hemodialysis patients and may, in fact, be associated with greater mortality,” Dr. Brunelli said. “In part, this may relate to compromised intake of other essential macronutrients—such as protein—that occur unintendedly when low phosphate diets are prescribed, which may offset or supersede any beneficial effects on phosphate mitigation.” 

He and his colleagues published their findings online ahead of print in the Clinical Journal of the American Society of Nephrology, where the authors noted: “Our results suggest that there is little reason to favor the prescribed withholding of phosphate among hemodialysis patients, particularly in light of recent data suggesting that phosphate binders may improve survival in this population.”