Renal disease - diet

Alternative names 
Diet for people with chronic kidney disease; Kidney disease - diet

Definition
A low-protein diet is used in people with abnormal kidney function to prevent worsening of their kidney disease. The diet is often low in sodium and potassium as well. For some people on this diet, fluid restriction is also necessary. And if you have diabetes along with kidney disease, a low-carbohydrate diet may be necessary.

Function
This special diet is very helpful because it decreases the stress on the kidney.

     
  • Protein is restricted to decrease the protein load on the kidney and slow down the progression of kidney disease.  
  • Sodium may be restricted to improve blood pressure control and to avoid fluid accumulation.  
  • Potassium is restricted if it is not excreted effectively and levels in the blood are high. When you have too much potassium in your blood, dangerous heart rhythms may result.

The controlled amounts of each of these nutrients are based on the blood levels of potassium, sodium, protein (measured as total protein and albumin), and urea (a waste product normally excreted in the urine).

Fluid is only restricted if you accumulate excessive amounts in your body.

Calcium and phosphorus, two other important minerals in the body, are also followed closely. Phosphorous can become too high if you have kidney disease. Calcium can become too low. If the blood levels of these two minerals indicate that you need to adjust your intake of them, then the amounts allowed in your diet are altered. If that alone is not enough, supplements and medications are used.

Food Sources

If you have kidney disease, you should get most of your calories from complex carbohydrates. In other words, you should tend to consume carbohydrates instead of proteins. Calories from fats should be from monounsaturated and polyunsaturated fats.

If you are diabetic, your dietitian and doctor will help you focus on low to moderate carbohydrates along with an emphasis on healthy fats.

Your kidney specialist should refer you to a registered dietitian for nutrition information specific to kidney disease - some even specialize in kidney diets. The Kidney Foundation has chapters in most states and is an excellent resource for programs and educational materials for people with kidney disease and their families.

Side Effects

A low-protein diet can be deficient in:

     
  • some of the essential amino acids  
  • the vitamins niacin, thiamine, and riboflavin  
  • the minerals calcium and iron

In advanced kidney disease, a low-protein diet can lead to malnutrition and should only be implemented under the guidance of a kidney specialist.

Recommendations

Low-protein diets may prevent or slow the progress of some kinds of kidney disease. The amount of protein you can eat is based on how well your kidneys are functioning and the amount of protein needed to maintain good health.

The amount of protein allowed in your diet is determined by checking the amount of protein (and protein waste byproducts) in your blood as well as some other laboratory tests. The suggested amount of protein in a low-protein diet is 0.6g/kg/day.

If you have a type of kidney disease (such as nephrotic syndrome) that leads to loss of large amounts of protein in your urine, your kidney specialist will recommend a moderate protein restriction of 0.8g/kg/day.

How sodium and potassium are restricted, and by how much, depends on the level of these electrolytes in your blood. Reducing sodium in your diet helps you control high blood pressure and avoid congestive heart failure.

In addition to sodium and potassium, the mineral phosphorus often needs to be controlled. To do this, you may be told to reduce intake of dairy products and other foods high in phosphorus. You may need to take supplements of calcium to prevent bone disease and vitamin D to control the balance of calcium and phosphorous in the body .

If dietary measures to lower phosphorus are not enough, “phosphorus binders” may be recommended by your doctor. These medications bind the phosphorus in your food and make them unavailable to your body.

When you have kidney failure, the amount of urine your body produces may decrease. The amount of fluids you can drink each day is based on the amount of urine you produce in a 24-hour period. Other considerations on whether fluid must be restricted are the amount of fluid you retain, the level of sodium in your diet, whether you use diuretics, and whether you have congestive heart failure.

Your daily calorie intake needs to be enough to keep you healthy and prevent the breakdown of body tissue. Your weight and protein status should be monitored regularly, sometimes even daily.

Vitamin supplementation is very individualized. It depends on your various dietary restrictions and the extent of kidney damage. Your requirements for vitamins A, E, and K are usually met by what you eat. Your intake of the B vitamins and vitamin C is usually adequate unless you begin dialysis.

The recommended supplementation of calcium is 1,000 to 1,500 milligrams per day. Magnesium supplementation is NOT recommended, as it can cause an increase in the magnesium levels in the blood if you have kidney disease. Iron is usually supplemented because most patients with advanced kidney failure also have severe anemia; the amount would be determined by your doctor.

Johns Hopkins patient information

Last revised: December 4, 2012
by Harutyun Medina, M.D.

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