The kidneys contain filtration units that remove wastes from the blood and ensure normal levels of fluid and electrolytes remain in the circulatory system. In people with normal kidney function, these organs maintain normal levels of sodium, potassium and phosphorus. In those who have impaired kidney function, the kidneys do not control the amounts of these substances as well as they should. Some people with impaired kidney function follow a special diet to control the condition.
Significance
The kidneys work with the nervous and endocrine systems to determine which substances to excrete in the urine and which to keep in the body. When a kidney disorder interrupts this tightly controlled system, the kidneys do not filter enough waste. They also allow minerals and fluid to accumulate in the bloodstream. Following a diet for healthy kidney function helps reduce levels of these substances in the body.
Features
When the body breaks down protein from the muscle cells, a byproduct called creatinine forms. The kidneys filter creatinine from the blood and eliminate it from the body in the urine. Eating high-protein foods increases creatinine production and makes the kidneys work harder to filter this waste product from the circulatory system. A kidney diet limits the intake of high-protein foods to reduce the workload of the kidneys and prevent additional damage.
Because people with kidney dysfunction have difficulty maintaining normal mineral levels, the diet also restricts the intake of foods high in potassium, sodium and phosphorus. Patients can avoid increased sodium levels by avoiding fast food, luncheon meats, canned soups and vegetables, frozen dinners, salted snack foods and cheese. The Davita website recommends that patients following this diet limit or avoid chocolate, nuts and seeds, ice cream, milk, salt substitute and high-potassium fruits and vegetables to reduce potassium levels in the blood. Reducing phosphorus levels involves limiting chocolate, potatoes, corn, dairy products, beer and colas.
Effects
Reduced levels of sodium, potassium and phosphorus have positive effects on people who have kidney disorders. Lower sodium levels prevent water retention and elevated blood pressure. Reduced potassium levels prevent a condition called hyperkalemia, the medical term for high levels of potassium in the blood. The Merck Manual for Healthcare Professionals explains that high levels of phosphorus--a condition known as hyperphosphatemia--can lead to low calcium levels and overactive parathyroid glands. Limiting the amount of phosphorus consumed reduces the risk for these complications.
Fluid Restriction
In the early stages of kidney disease, patients do not usually need to restrict the amount of fluid they consume. The American Association of Kidney Patients reports that people who develop kidney failure usually need to limit their fluid intake before they begin hemodialysis, a process that filters the blood when the kidneys fail. Fluid restriction involves limiting the beverages consumed each day, as well as limiting the consumption of soups, ice pops, ice cream, gravy, gelatin and other foods that turn into liquid.
Misconceptions
Some people think that the renal diet is the same for everyone who has kidney disease. Instead, dietitians customize this eating plan for each patient. The Edinburgh Renal Unit website explains that dietary restrictions depend on the patient's general health, kidney disease stage and other factors.
References
- Davita: Kidney Disease and Potassium
- The Merck Manual for Healthcare Professionals: Disorders of Phosphate Concentration
- American Association of Kidney Patients: What to Eat if You Have Chronic Kidney Disease
- Edinburgh Renal Unit: Diet in Renal Disease
- USC Keck School of Medicine: Foods High in Sodium (NA+) Content
