The kidneys do everything from filtering blood to regulating blood pressure and maintaining healthy levels of potassium and phosphorus. When kidneys become so impaired that they no longer support life, dialysis can do some of these functions. As evidenced by the high mortality rate of patients on dialysis, this solution is imperfect. If you are on dialysis, your quality of life is greatly improved by staying reasonably fit, getting enough calories, and vigilantly following the dietary suggestions of your nephrologist and renal dietitian,
Types of Dialysis
Hemodialysis involves using a dialyzer to clean the blood. Blood is removed from the patient, run through a filter and returned to the patient. Peritoneal dialysis involves using the patient's own peritoneal membrane as a filter. Surgeons implant a permanent catheter in the patient's belly. The patient uses this catheter to fill his peritoneal cavity with a dialysing solution. Several hours later, the patient removes this solution, along with all the impurities that it has drawn from the blood. Regardless what modality of dialysis you choose, diet is important because dialysis also removes nutrients from the blood.
Protein
Getting enough protein is critical for dialysis patients. Muscle wasting often affects these patients, who become cachexic. This is associated with increased mortality in patients on maintenance dialysis therapy, as noted in a study review article in the February 2010 issue of the "American Journal of Kidney Disease." Patients can prevent this by getting enough protein. If you are on dialysis, ask your nephrologist about how much extra protein you need. Low cholesterol sources of protein, such as chicken and fish, are ideal for dialysis patients. Although legumes are a good source of protein, they should be avoided if you have high serum phosphorus or potassium.
Phosphorus and Potassium
Dialysis patients often have high levels of phosphorus and potassium in their blood. Healthy kidneys closely regulate serum levels of these nutrients. Since dialysis cannot replace this function, low-potassium and low-phosphorus diets are often necessary. Controlling phosphorus levels is important because high levels of phosphorus leach calcium from the bones causing them to be permanently weakened. Controlling potassium levels is critical because high levels of potassium cause irregular heartbeats. Since dairy products, as well as bananas, potatoes, avocados, tomatoes and broccoli, are high in potassium, dialysis patients must consume them sparingly. Likewise, organ meats, beer, chocolate and legumes are prohibitively high in phosphorus.
Potassium and Phosphorus
In his textbook "Principles and Practice of Dialysis," William L. Henrich explains that dialysis strips water-soluble vitamins from the blood. For this reason, nephrologists often prescribe renal vitamins for dialysis patients. These vitamins contain vitamin C and all the necessary B vitamins. They intentionally exclude potassium, phosphorus and vitamin A because patients often have excessive levels of those nutrients. If your diet is restricted because you are on dialysis, ask your nephrologist whether renal vitamins are right for you.
References
- "Principles and Practice of Dialysis"; William L. Henrich; 2009
- "American Journal of Kidney Disease"; Association of the Malnutrition-Inflammation Score With Clinical Outcomes in Kidney Transplant Recipients; M.Z. Molnar et al.; Feb. 2011
- National Kidney Foundation: Phosphorus and your CKD Diet
- National Kidney Foundation: Potassium and your CKD Diet
- Davita: ABC's of Vitamins for Kidney Patients
