Unlike people in the early stages of kidney disease, those in the latter stages often need a highly restricted diet. As renal function gets progressively worse, the kidneys no longer regulate levels of phosphorus in the blood. Accordingly, patients must compensate for their lack of renal function by limiting their dietary intake of this mineral.
Phosphorus
Phosphorus is so ubiquitous that deficiencies are almost unknown outside of complete starvation. Nearly 1 percent of your body is made up of phosphorus. It combines with hydrogen and oxygen to form the hydroxyapatite that is found in your bones and teeth. Moreover, many biologically active molecules such as adenosine triphosphate, or ATP, contain phosphorus.
Kidneys and Phosphorus
Your kidneys filter over 200 gallons of blood every day. As they filter your blood, they remove excess phosphorus, which ends up in your urine. Normally, serum phosphorus levels are between 3.3 and 5.5 mEq/L. Your nephrologist will regularly monitor phosphorus levels in your blood and tell you if your levels are too high. If necessary, he will tell you how much phosphorus you can safely eat.
Tips
A phosphorus-restricted diet is difficult to follow because it is nearly impossible to know what foods have high levels of phosphorus. Since the law does not require food producers to report the phosphorus content of food, most patients consult a nutritional database, such as the one provided by the United States Department of Agriculture. Dairy foods, legumes, colas, chocolate and beer are high-phosphorus foods.
Your nephrologist may also suggest that you take phosphorus binders with meals to prevent high levels. Phosphorus binders are often calcium-carbonate preparations, such as TUMS. They bind to the free phosphorus in food.
Warning
Newly-diagnosed patients are understandably the most eager to do everything they can to preserve what renal function they have and often limit phosphorus intake unnecessarily. There is no benefit, however, in embarking on a phosphorus-restricted diet prematurely. Lowering your intake of dietary phosphorus does not have a preventative benefit.
