Patients with advanced kidney disease are often given elaborate dietary guidelines. For example, patients are often told to avoid dark sodas, such as colas, and drink clear sodas instead. There are good common sense reasons for this kind of restriction. Avoiding colas and other high phosphorus foods is important for some patients whose kidneys cannot remove phosphorus from the blood.
Phosphorus Regulation
Maintaining healthy levels of phosphorus and calcium is essential to having healthy teeth and bones. Since most foods contains phosphorus, deficiencies are very rare. When blood levels of phosphorus get too high, the kidneys remove the excess phosphorus from the blood. The kidneys of patients with advanced disease often cannot perform this function. When their serum phosphorus levels exceed 5.5 mg/dl, nephrologists often recommend a low-phosphorus diet.
Phosphorus and Labeling
The law does not require food producers to provide information on the phosphorus content of food. Kidney patients often consult a database such as the one provided by the U.S. Department of Agriculture to determine how much phosphorus is in a food. A 12-oz. can of cola has 37 mg of phosphorus. Diet sodas have approximately the same amount of this mineral. By way of comparison, clear sodas, such as Sprite, have no phosphorus at all.
Consequences
High levels of phosphorus in the blood begin to pull calcium from the bones. This permanently weakens them, and makes the patient more vulnerable to broken bones. The high levels of circulating calcium become deposited in blood vessels, eyes and heart tissue where they cause other problems. These problems can be avoiding by avoiding high phosphorus foods such as colas, beer, chocolate and dairy products.
Warning
Never embark on a low-phosphorus diet without consulting your nephrologist first. Restricting phosphorus intake is only meaningful if phosphorus levels are high to begin with. There is no preventative benefit in limiting phosphorus intake if serum levels of phosphorus are normal.
