Dietary adjustments for kidney patients are always made in response to lab values, blood pressure and physical examination. Nephrologists often have no particular advice for patients in the early stages of disease, other than to "eat sensibly." This is not bad advice because as kidney disease advances, dietary restrictions become more onerous.
Potassium Function
Healthy kidneys keep serum potassium levels within a very narrow range. The concentration of potassium on either side of a neuron's membrane makes it possible for the nerve to fire. If potassium levels are too high -- as they often are in patients with advanced kidney disease -- the nerve misfires, causing irregular heartbeats. This can have fatal consequences.
Potassium Restriction
Since high levels of serum potassium are so problematic, your nephrologist may recommend potassium restriction if your potassium levels exceed 5.0 mg/dl. Many healthy foods, such as berries, melons, oranges, bananas, squash and spinach, are high in potassium, so you must eat them sparingly. To find what foods are high in potassium and how much of a food is safe to eat, kidney patients often refer to the U.S. Department of Agriculture potassium counter.
Sodium
Hypertension and kidney disease go hand-in-hand. When the kidneys filter less blood, they secrete a hormone that causes constriction of the blood vessels, which raises blood pressure. This creates a vicious cycle, because high blood pressure destroys kidney tissue, which lowers the filtration rate still further. Management of hypertension is a key element of treatment. In addition to medication, nephrologists recommend that patients follow a low-sodium diet. Your nephrologist will tell you how much sodium is safe for you to eat.
Protein
In the early stages of kidney disease, nephrologists may advise that patients with high urine protein eat less protein.The rationale for this advice is that urine protein can be somewhat controlled by dietary intake. This is a fairly extreme step, however, and should never be taken without your doctor's advice.
In the late stages of disease, hemodialysis patients are urged to eat more protein. Eating low-cholesterol protein like fish and chicken helps replace some of the amino acids that are removed from the blood by dialysis.
Phosphorus
Patients with advanced kidney disease often have elevated levels of serum phosphorus. This can cause problems, because the phosphorus starts pulling calcium from the bones. If your serum phosphorus levels get higher than 5.5 mg/dl, your nephrologist may recommend phosphorus restriction. Dairy products, bran, chocolate and beer are high-phosphorus foods and should be avoided.
