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What is the role of diet in kidney disease?

The kidneys are often referred to as the body's "master chemists" because they constantly adjust the body's chemical balance of fluids, electrolytes, and acids. The kidneys filter waste products and extra fluid from the blood for disposal in the urine, while returning protein, glucose and other essential nutrients to the bloodstream. They also help control blood pressure and are instrumental in making red blood cells and maintaining strong bones.

A carefully planned diet for people with kidney disease can slow the progression of the kidney disorder and delay the need for dialysis. Diet is especially critical for patients who require regular kidney dialysis, in which wastes are removed from the bloodstream by mechanical devices. Patients who undergo a kidney transplant may also need to follow a special diet because of the medications needed to prevent the body from rejecting the new kidney.

When should I use a diet for kidney disease?

When a person develops chronic kidney disease, the kidneys slow down and perform their many functions less efficiently. In such circumstances, diet is especially important in easing the workload of the kidneys and controlling metabolic problems that may contribute to the kidney disease. For example, by controlling the types and quantities of the food and fluids in the diet, a person can reduce the accumulation of waste and fluids in the blood.

Who provides diets for kidney disease?
In general, the diet must be individualized to meet the specific needs of the patient. This is usually done by a registered dietitian working directly with the doctor.

What should I expect of a diet for kidney disease?

The specific diet depends upon the type of kidney disease. For example, a person who has kidney stones may need to increase fluid intake and restrict the intake of calcium to prevent new stones from forming.

A diet for patients suffering from chronic or progressive kidney failure is more difficult to formulate because it must minimize the workload of the kidneys and still provide adequate nutrition to maintain a desirable body weight and enough fluid to prevent dehydration. In addition to fluid, the most important nutrients to

control are protein, potassium, sodium, and phosphorus, each of which are restricted to varying degrees. In general, patients whose kidneys are failing, but do not yet require dialysis, should reduce their intake of protein, sodium, and phosphorus. Fluid intake may also be reduced, depending upon the degree of kidney function.

Levels of potassium and calcium should be carefully monitored with periodic blood tests, and the diet adjusted or supplements added as needed.

Cutting back on protein is important to reduce production of urea, a waste product of protein metabolism, in the blood. The task is to provide enough high-quality {complete) protein to meet the body's needs and still minimize the production of urea. In general, small quantities of low-fat animal products such as low-fat milk, egg whites, fish, trimmed meat, and skinless poultry are preferred because they provide all the essential amino acids needed to maintain body tissue. In contrast, plant protein from legumes, grains, and vegetables is incomplete, and must be consumed in combination and in larger quantities to meet nutritional needs. Thus, only limited amounts of these foods may be allowed.

Dietary restrictions may make it difficult to obtain adequate amounts of certain vitamins and minerals. Thus, supplements of vitamins B and C, folic acid, and calcium may be needed.

If the kidney disease progresses to the point where dialysis becomes necessary, a different diet is needed. In general:

• The intake of protein is increased.
• Sodium is restricted.
• The intake of fluids is limited.

• Foods that are high in potassium and phosphorus are restricted.
• Supplements of calcium and vitamins B 6 C, and folic acid are added.
• Iron supplements may be prescribed if the patient develops anemia.

What should be expected of me?

Each patient is in charge of applying the dietary guidelines provided by a doctor and dietitian to his or her daily life. In the beginning, it may be necessary to keep a careful diary to record the intake of all food and fluids and to check this diary against the prescribed diet. In addition, most patients with kidney disease are instructed to measure and record fluid intake and urine production.

Certain vitamin and mineral supplements may be needed, but should be taken only on the specific recommendations of the doctor or dietitian. Excessive amounts of vitamin C and certain other nutrients can exacerbate the kidney problems and result in metabolic imbalances.

Frequent physician visits are necessary for blood tests to measure levels of potassium, calcium, and certain other nutrients.

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