NEW YORK (Reuters Health) - People with advanced kidney disease are taught to avoid certain foods that are naturally high in the mineral phosphorus, which is difficult for their compromised kidneys to get rid of. But in a report published Wednesday, researchers warn that a fair amount of processed and fast food actually contains phosphorus additives, which can be just as harmful for people with advanced kidney disease.

Because high blood levels of phosphorus can lead to heart disease, bone disease, and even death among patients with advanced kidney disease, these patients must avoid certain meats, dairy products, whole grains, and nuts that are naturally high in phosphorus, the researchers note in the Journal of the American Medical Association.

The problem, according to Dr. Ashwini R. Sehgal and colleagues at Case Western Reserve University in Cleveland, Ohio, is that it has become an increasingly common practice by food manufacturers to include phosphate salts to processed foods.

These additives are used to enhance flavor and shelf life -- particularly in meats, cheeses, baked goods, and beverages -- and it is very hard for consumers to know whether or not these additives are present in products.

In a study of 279 kidney disease patients who had elevated blood phosphorus levels, Sehgal and colleagues were able to significantly lower phosphorus levels by teaching patients to avoid foods containing phosphorus additives.

In the randomized study, 145 "intervention" patients were given lists of common phosphorus-containing additives to check against food items at grocery stores and fast food menu items with high phosphorus content and healthy alternatives. The remaining 134 "control" patients received standard care.

After three months, phosphorus levels declined two and a half times more in patients who were taught how to avoid phosphorus additives than in the control group.

The investigators recommend mandating phosphorus content on food labels, and creating incentives for marketing low-phosphorus products to improve the health of patients with kidney disease, and the general public as well.

SOURCE: Journal of the American Medical Association, February 11, 2009.

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