Uncooked meat products enhanced with food additives may contain high levels of phosphorus and potassium that are not discernable from inspection of food labels, according to a study appearing in an upcoming issue of the Clinical Journal of the American Society Nephrology (CJASN). This can make it difficult for people to limit dietary phosphorus and potassium that at high levels are harmful to kidney disease patients.

Kidney disease patients on dialysis must watch their intake of dietary phosphate so that their blood phosphate levels do not rise. This is important because high blood phosphate levels may cause premature death in dialysis patients. Kidney disease patients also must limit their intake of potassium, because high blood potassium levels can cause sudden death.

One growing source of dietary phosphorus and potassium is through "enhanced" fresh meat and poultry products. These foods are injected with a solution of water with sodium and potassium salts (particularly phosphates) as well as antioxidants and flavorings. While ingesting phosphates and potassium can be dangerous for dialysis patients, there is no requirement that these ingredients be included in nutrition labels. There also have been no studies on the levels of phosphates and potassium contained in fresh meat and poultry products that have been "enhanced."

Richard Sherman, MD, and Ojas Mehta, DO (University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School), examined the potassium and phosphate content in a variety of "enhanced" and additive-free meat and poultry products available in local supermarkets. They found that products that were labeled as "enhanced" had an average phosphate concentration that was 28% higher than additive-free products, with some products almost 100% higher. Potassium content was variable. Additive-free products all contained < 387 mg of potassium per 100 gm of protein while 5 of the 25 products with additives that were studied contained at least 692 mg of potassium per 100 gm of protein (maximum 930 mg/100 gm). Most foods with phosphate and potassium additives reported the additives on the labeling; however, 8 of the 25 "enhanced" products included in the study did not list the additives.

"The burden imposed on those seeking to limit dietary phosphorus and potassium could be ameliorated by more complete food labeling by manufacturers," the authors wrote.

The study was funded by grants from Genzyme, Inc. and Dialysis Clinics, Inc.