Dietary Aid Helps Kidney Patients Stay Safe

Too much phosphorus in food can cause harm, but new tool helps spot the danger

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TUESDAY, Feb. 10, 2009 (HealthDay News) -- Too much dietary intake of phosphorus can be dangerous for people with kidney disease, but a new educational aid helps patients reduce the risk, a U.S. study finds.

Patients with moderate to severe kidney disease have difficulty excreting phosphorus, which can lead to a buildup of the chemical. Elevated blood levels of phosphorus (hyperphosphatemia) increase the risk of illness and death. Patients with kidney disease are advised to limit their intake of foods that are naturally high in phosphorus, such as meats, dairy products, whole grains and nuts. But phosphorus-containing additives are increasingly being added to processed and fast foods, according to background information in the study.

It included 279 end-stage renal disease (ESRD) patients with elevated serum (blood) levels of phosphorus (greater than 5.5 milligrams per deciliter (mg/dL). Some of the patients (145) received education on avoiding foods with phosphorus additives when purchasing groceries or going to fast-food restaurants, while the remainder (134) continued to receive usual care.

At the start of the study, the average serum phosphorus level was 7.2 mg/dL in the intervention group and 7.1 mg/dL in the control group. After three months, those levels declined by 1.0 mg/dL in the intervention group and by 0.4 mg/dL in the control group. Patients in the intervention group were also much more likely to read ingredient lists and nutrition facts labels on food products.

The study was published in the Feb. 11 issue of the Journal of the American Medical Association.

"The 0.6 mg/dL larger decline in average phosphorus level among intervention participants compared with control participants corresponds to a 5 percent to 15 percent reduction in relative mortality risk in observational studies," wrote a team led by Catherine Sullivan, of MetroHealth Medical Center and Case Western Reserve University in Cleveland.

"Our findings raise the possibility that typical intakes of processed and fast foods contribute to the persistent hyperphosphatemia, cardiovascular events, and bone disease observed among patients with ESRD. Our results have important implications for patients, clinicians, researchers, and policy makers," the study authors wrote. "Patients with ESRD and clinicians should learn about both naturally occurring phosphorus and phosphorus-containing additives, and patients should limit their total phosphorus intake to 800 to 1,000 milligrams per day as recommended by practice guidelines."

They added that researchers should focus on developing improved methods of preventing and treating hyperphosphatemia, and policy makers should consider ways to tackle the problem, such as mandatory listing of phosphorus content on nutrition labels.

More information

The U.S. National Kidney Disease Education Program has more about kidney disease.

SOURCE: Journal of the American Medical Association, news release, Feb. 10, 2009


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