Nutrition for kidney diseases

Synonyms in a broader sense

renal insufficiency, renal failure

Chronic renal insufficiency

Chronic renal insufficiency (functional impairment) is characterized by the fact that, as a result, urinary substances, in particular urea, uric acid and creatinine, increase in blood serum and at the same time the amount of filtrate in the kidney decreases. The disease process more or less progresses and a cure is no longer possible. The most important therapeutic goal is therefore to delay or stop the progression of the disease.

Within 24 hours, the healthy kidney produces approximately 1 – 1.5 l of urine with which the waste products are excreted and whose blood concentrations remain within the norm. If a healthy person drinks large amounts of fluids, the amount of urine increases, but if he or she is thirsty, the kidney only excretes a small but highly concentrated amount of urine. The sick kidney is no longer capable of this concentration work.

The kidney has an enormously high performance reserve and this fact is also evident in the fact that humans can normally survive with only one kidney. If the kidney becomes diseased, the remaining healthy tissue can take over the necessary tasks for a long time.

  • Excretion of end products of the metabolism, in particular of the protein metabolism such as urea, creatinine and uric acid, which accumulate in the body when the kidney is malfunctioning, which can lead to uremia (self-poisoning).
  • Regulation of the water and salt balance such as sodium, potassium, calcium, phosphorus and the acid-base balance
  • Build up and breakdown of hormones.

In chronic kidney disease, the kidney initially only loses the ability to produce concentrated urine.

For the waste products to be excreted, sufficient water must therefore be available and 2-3l must be drunk daily. With this ample drinking quantity, the kidney can continue to excrete the urinary waste products in sufficient quantities. One speaks of stage I, the so-called “full compensation” of kidney disease, in which a special diet is not yet necessary.

As the disease progresses, the urea and creatinine levels in the serum are considered to be the main indicators for the start of a protein-restricted diet. In cases of moderate restriction of kidney function (compensated retention), a serum creatinine level of 3 – 6 mg/dl and a urea level below 150 mgdl, a protein intake of 0.5 – 0.6 g per kg body weight is recommended. A lactovegetable diet consisting of vegetable foods, milk and dairy products is recommended.

As soon as serum creatinine exceeds 6 mg/dl, a strictly low-protein diet with 0.35 g to 0.45 g protein per kg body weight becomes necessary to reduce symptoms such as nausea, vomiting or loss of appetite and to increase the patient’s quality of life. At this stage, the kidney’s reduced ability to excrete can be positively influenced by an appropriate diet adapted to creatinine levels and a balanced water balance. Based on the creatine and urea levels in the blood, the doctor can determine the progression of the disease and prescribe the necessary diet.

This primarily results in a restriction of the protein intake with food. Essential amino acids are given in tablet form if required. The water and salt intake must be individually adapted to the loss of kidney function.

There are several of these low-protein diets, all of which include an energy-rich basic diet combined with a diet that must be rich in essential amino acids. The best known diets are the “Potato-Egg Diet” according to Kluthe and Quirin and the “Swedish Diet” according to Bergström. Both diets are described in detail in the chapter “Practical Nutritional Therapy for Chronic Kidney Failure”.

Chronic end-stage renal failure (terminal renal insufficiency with a creatinine level of more than 10mg/dl in serum) can only be controlled by dialysis (blood washing) or transplantation. Special diets are indicated for hemo- or peritonal dialysis. More information about these diets can be found under our topics:

  • Potato-Egg-Diet
  • Swedish Diet

Protein is an important building material in our body and essential for life.

We absorb protein from protein-containing foods such as meat, eggs, milk and dairy products and vegetable foods every day. The smallest building blocks of protein are the amino acids.There are some of these amino acids that the body itself cannot produce and that we need to take in with our food to stay healthy. Their supply is absolutely necessary for the build-up of the body’s own protein such as muscles, skin, all internal organs, hormones and digestive enzymes.

The dietary protein, of which we take in an average of 70 to 100 g daily, is broken down into amino acids in the intestines and released into the blood. In this way the amino acids are transported to where they are needed. Amino acids are also broken down in the body from surplus food protein on the one hand and from the body protein which is constantly renewed on the other.

In the process, urea is created as a metabolic end product. This is excreted through the kidneys. From a certain degree of damage to the organ, urea can no longer be excreted sufficiently and its concentration in blood serum increases.

This leads to further disturbances in protein metabolism and patients complain of fatigue, nausea, vomiting and loss of appetite. At the same time, the concentration of other toxic substances (e.g. creatinine) in the blood serum increases, which also originate from protein metabolism. Keeping the blood urea level as low as possible is an important goal in the dietary management of chronic renal insufficiency.

This is achieved by limiting the protein intake. However, there is always the risk of an undersupply of essential amino acids. One is therefore faced with the problem of taking in just enough protein to prevent the blood urea level from rising and yet still supplying sufficient amino acids.

This problem can only be solved by using only foods with very high quality protein as protein suppliers. Only foods whose protein content of essential amino acids is sufficient to cover the demand (full value) are allowed. In addition, there is the possibility of combining certain foods, as is the case, for example, with the potato and egg diet.

With this form of diet, the difficulty of only a very limited choice of food arises. Other protein-rich foods such as meat, fish and poultry have to be practically completely banned and thus this form of diet can become too monotonous and stressful for the patient in the long run. Following this problem, Bergström developed the so-called “Swedish diet”.

In this “protein-balanced diet”, the protein intake is of course also to be limited according to the severity of the renal insufficiency. However, within the permitted protein quantity, all foods may be eaten without having to pay attention to their value (content of essential amino acids). The supply of the essential amino acids takes place here in the form of drugs, for example EAS oral tablets to be taken with meals.

However, the high number of tablets sometimes causes problems. Granules with the same ingredients often cause an unpleasant aftertaste. The supply of amino acids can also be done with the help of their precursors, the so-called keto acids, which are available in the form of tablets, beads or granules.

These are mainly used in cases of advanced renal insufficiency because they put less strain on the kidneys and produce less urea. In addition to a controlled protein intake, sufficient energy supply is of particular importance for a successful dietary therapy of renal insufficiency. If the calorie intake is insufficient, the body’s own protein and the small amount of dietary protein supplied is used to supply energy.

This leads to an undesirable increase in urea. To cover the energy supply requirements, at least 35 kilocalories per kg body weight should therefore be consumed every day. Carbohydrates and fat serve as energy sources.

Vegetable fats should be given preference in the selection of fat. For example, rapeseed oil, sunflower oil, corn oil and olive oil are recommended. A loss of body weight must be prevented and regular weight control is recommended.

A restriction of sodium (common salt) is not necessary in chronic kidney diseases. However, kidney patients often have water and sodium retention in the body. As a result, edema (accumulation of water) occurs under the skin and (or) in the blood vessels and high blood pressure develops.

In this case a sodium restriction becomes necessary. The salt intake should not exceed 3 – 5 g per day.One reaches this already by very economical handling with common salt with the food preparation, the recommendation with table in no case “zusalzen”. Highly salty foods must be removed from the menu.

Sodium depletion rarely occurs due to salt loss via the kidneys or diarrhea and vomiting. In these cases, more salt and liquid must be taken in with the food. In cases of higher salt losses, sodium can also be given by means of an infusion.

Salt intake in chronic renal insufficiency can vary greatly from person to person. The permitted intake of the mineral potassium also varies from case to case. In the case of advanced renal insufficiency, life-threatening hyperkalemia (potassium values in blood serum above 6 mmoll) can develop.

To avoid this, foods rich in potassium must be removed from the diet. Foods with very high potassium content and unsuitable:

  • Bouillon cubes, meat extract, salt-reduced sausage, meat and fish preserves, stockfish.
  • Broccoli, spinach, fennel, mushrooms, kale, peas, corn, chard, tomatoes, legumes, sprouts and germs, tomato ketchup, tomato paste and vegetable juices
  • Potato products of all kinds.
  • Apricots, banana, kiwi, avocado, honeydew melon, fruit juices, dried fruits of all kinds, nuts and seeds.
  • Whole grain products (crispbread, whole grain bread in larger quantities, pumpernickel, bran, grains, cereal flakes, muesli, muesli mixes), whole grain rice, whole grain noodles.
  • Chocolate and all sweets made with chocolate.
  • Cocoa and cocoa-containing drinks
  • Potassium-based table salt substitute.

All spices (in case of sodium restriction, please observe the intake of table salt and do not use table salt substitutes with a high potassium content! ), fresh herbs only in very small quantities.

For potatoes, vegetables and frozen vegetables, which are allowed and suitable within the framework of the diet plan, the potassium content can be reduced by 2/3 by cutting them into small pieces, watering them afterwards (24 hours) and draining the cooking water several times. The vitamin losses with this kind of preparation are to be compensated by the intake of water-soluble vitamins (vitamin C and B vitamins) in tablet form A hypokalemia (potassium values in the blood serum too low) occurs with chronic renal insufficiency (chronic kidney failure) only in exceptional cases It often manifests itself in muscle cramps and can be positively influenced by a potassium-rich diet. Effervescent tablets can also be used.

  • Fresh meat, fresh fish and fish products of all kinds up to 120 g daily
  • Sausages of all kinds preferably liver sausage, mortadella, mettwurst
  • Milk and dairy products all sorts
  • Fats preferably vegetable oils for cooking and salads, butter
  • 1-2 eggs per week
  • 1no portion of lettuce daily (30g) and up to 200 g of vegetables (not potassium-rich! ), 150 g of potatoes
  • 150 g of cooked fruit (not potassium-rich!) without liquid.
  • 100 g fresh apple, pear, watermelon or 200 g fresh blueberries or cranberries.
  • White bread, brown bread, toast, rusk, wholemeal bread in small quantities
  • (30 g daily), rice, noodles, semolina, cornflakes
  • Sugar and sweets without chocolate in any quantity.
  • Malt coffee, tea, lemonade.

    Coffee, wine and beer in small quantities.

  • Water, mineral water (with sodium restriction sodium content less than 20 mg per liter)

In chronic renal insufficiency, changes in the mineral balance of calcium and phosphorus occur. If the creatinine level in the serum rises above 3 – 5 mgdl, phosphorus is excreted via the kidneys in a reduced form and the blood level rises. As a result, the calcium level in the serum can drop (hypocalcaemia).

This leads to disorders of bone metabolism and in the long term to bone diseases. Therefore, the daily phosphate intake with food should be limited to 1g. All phosphate-rich foods must be removed from the diet.

In case of moderate renal insufficiency, this measure is already sufficient to keep the phosphate level within the norm. In addition to these nutritional recommendations, a drug-based reduction of the phosphate level may be necessary. The mineral calcium may be insufficiently absorbed even in the early stages of renal insufficiency.

The protein-reduced form of nutrition that is necessary in renal insufficiency excludes an increased intake of calcium.The most important calcium-rich foods are milk and dairy products, which must be severely restricted due to their high protein content. Calcium must therefore be supplied in the form of medication. In the context of a protein-reduced diet, the vitamin supply is often insufficient.

The supply of B vitamins and vitamin D is often insufficient. The B vitamins are primarily lacking in vitamin B6 and folic acid. The administration of all water-soluble vitamins in tablet form has proven to be effective.

The administration of vitamin D becomes necessary when renal osteopathy (increased bone resorption) continues to progress despite a low phosphate diet and the administration of calcium-containing phosphate binders in tablet form. In a low potassium diet, where watering of certain foods is necessary, the water-soluble vitamins C and B are missing in any case. On the other hand, the vitamin A level is often elevated in chronic renal insufficiency and intake is not appropriate.

  • Processed cheese, Camembert, Emmental, Edam, Chester, milk powder.
  • Oil sardines, smoked halibut
  • Wheat bran, wheat germ, oat flakes, wheat germ, brown rice, crispbread, wholemeal wheat bread
  • Porcini (dried), legumes.
  • Peanuts, Brazil nuts, walnuts, almonds
  • Cola drinks
  • Foods with added phosphate such as sausages.

An intake of iron can also be necessary in a low-protein diet. In case of existing complaints (for example impotence), the trace element zinc must also be given in tablet form. While with moderate restriction of the kidney function 2 – 3 liters per day should be drunk to remove the urinary substances, with progressive illness the ability of the organ from liquid sufficiently to excrete decreases.

This process varies greatly from patient to patient. The aim is to avoid overhydration at this stage because it could lead to life-threatening pulmonary edema. The amount of fluid allowed depends on the doctor’s prescription. The basic rule for the permitted amount of fluid is: amount of urine excreted the day before plus 500 ml.