Consultant Dietician, Mumbai*
Chronic renal failure (CRF) is a disease in which the kidneys gradually stop working over a period of few years.
In a healthy body, the kidneys filter waste and other impurities from the blood. In people with CRF, toxins that the kidneys normally eliminate in urine slowly build up in the body. The most commonly measured of these toxins are urea-a nitrogen waste product and creatinine. The amount of toxins in the blood roughly indicates how well the kidneys are working. In CRF the nephrons (functional unit of kidneys) are gradually and progressively destroyed and the remaining nephrons hypertrophy (increase in size) to maintain normal functioning of the kidney..With the destruction of 80% of nephrons, the functions are affected seriously and the patient goes into uremia (presence of large amounts of end products of protein metabolism such as urea, creatinine, uric acid in blood) characterized by nausea, vomiting, headache, diminished vision and at times convulsions.
Signs and symptoms: The symptoms associated with CRF are progressive weakness, shortness of breath, lethargy, fatigue, weight loss, anorexia (loss of appetite), mouth ulceration, metallic taste, frequent hiccups, increased aches and pains in joints due to osteodystrophy(bone disease), increased or decreased urine output depending on the stage of CRF.
Causes and risks: A primary kidney disease may cause CRF. It may also be due to other diseases that affect kidneys such as diabetes, high blood pressure, glomerulonephritis (the swelling of the glomerulus which is the part of the kidneys consisting of blood vessels and nerve fibres), polycystic kidneys (a condition in which the kidneys become enlarged and grow cysts), uropathy (any condition that blocks the flow of urine) or cancer of the bone marrow.
Since many diseases lead to CRF, the diagnoses of diseases causing CRF can vary. There are a few common abnormalities associated with the condition. For instance: Urinalysis may show protein, red blood cells or different types of casts (structures made when minerals collect on the walls of the kidney). A blood sample may show elevated creatinine and urea nitrogen which are both toxins. Levels of erythropoietin- a hormone produced by the kidneys may be low. Levels of serum potassium, phosphorus, Parathyroid hormone, magnesium may be high with/without low levels of calcium. Malnourishment can occur. Treatment involves dialysis at regular intervals with ultimately renal transplant.
PRINCIPLES OF DIETARY MANAGEMENT
Because uremia is seen in advanced renal insufficiency, the diet must take into account not only the protein content but also the acid-base balance and fluid and electrolyte balance too.
However in the world of modern scientific inventions, dialysis has proved to be a boon. In this technique, the toxins from the body are artificially cleared by a semipermeable membrane either from the blood (hemodialysis) or from the abdomen (peritoneal dialysis). The dietary modification must take into account the following considerations.
- To provide adequate calories
- To regulate the protein content of the diet
- To regulate sodium, potassium and fluid intake
- To restrict phosphate and supplement the diet with calcium, iron, trace minerals, ascorbic acid and the B-complex vitamins,
- To aim for palatability (taste).Most diets fail to achieve their aims simply because children are unable or unwilling to tolerate them.
- To avoid starvation and to feed the children frequently. Renal function deteriorates and blood urea levels rise rapidly owing to tissue breakdown under conditions of starvation.
Energy: Energy is derived from foods, which contain carbohydrates, proteins and fats. Sufficient energy should be provided in the diet or else the body tissues will be broken down to provide energy. This should be avoided as all tissues are mainly protein in nature and if broken down they increase the urea and creatinine levels.
Protein: The body reserves proteins for growth, maintenance and repair of body tissues. It is important for every cell in the body. It is present in almost all the foods but the quantity and quality varies. Proteins of high biological value or 'good quality' are found mainly in eggs, milk, meat, fish and poultry. Proteins of lower biological value are found in pulses, cereals, nuts, oilseeds and in some vegetables like green peas and dried beans. Normally 0.8-1.0gm/kg of body weight protein is effective.
Sodium: Sodium restriction is necessary when the body retains sodium and water causing oedema or 'swelling'. Sodium is found in almost all foods but in different amounts. Protein foods are naturally high in sodium. Some vegetables and seafoods are also high in sodium content. Fruits in general have a low content of sodium.
|FOODSTUFFS HIGH IN SODIUM|
|Salted wafers, popcorns, salted biscuits.|
|Papads - all varieties.|
|Salted pickles, chutneys, curry powder - commercial.|
|Commercial salad dressings and sauces.|
|Soft drinks containing sodium benzoate.|
|Bakery products, bread , biscuits.|
|Nuts such as salted cashew nuts, pistachio, walnuts, peanuts.|
|Preservative containing foods.|
|Canned and tinned foods.|
|Sea food, chicken, dry fish, bacon, ham .|
|Meat and yeast extracts like marmite.|
|Proprietary drinks - Bournvita , chocolate drinks , Horlicks.|
|Milk and curds.|
|Pulses and legumes - all varieties.|
Potassium: In patients with CRF, the ability to eliminate excessive amounts of potassium is decreased. If the potassium level in the blood is elevated, it causes complications. Potassium is found naturally in almost all foods of both plant and animal origin. Salt substitutes in the market may contain potassium and labels should be checked. Two methods of reducing potassium (leaching) in the foods are given below:
- Method 1: Wash, peel and cut vegetables into small pieces. Soak in warm water for 2-3 hours. Discard water. Add large volume of fresh water and cook vegetables. Discard water.
- Method 2: Peel vegetables and cut into small pieces. Bring to a boil in a large quantity of water. Discard water and cook in a large volume of fresh water. Discard excess water.
|Foods low in potassium: |
|-Rice, semolina (rawa) |
Vegetables such as cucumber, ridge gourd
(turai), snake gourd (padwal), tinda, broad beans,
beetroot, fenugreek leaves (methi), green mango,
pink radish, bottle gourd (dudhi).
-Fruit such as apple(1/4),pineapple(1/4), guava,papaya, pear.
-Chicken and meat-boiled in excess water twice and drained.
|-Foods moderate in potassium: |
|-Rice flakes, corn flakes, bambino vermicelli. |
-Vegetables such as carrot, cauliflower, lady finger, tomatoes, Bitter gourd, onions, cabbage, white radish, pumpkin, brinjal, French beans.
|-Foods high in potassium: |
-Barley, ragi, wheat flour.
-All leafy vegetables such as amaranth, coriander leaves, drumstick leaves, spinach; potato, colocasia, sweet potato, yam, drumstick, Greenpapaya, sword beans.
-Milk, fish especially sardines
-Nuts such as cashew nuts, almonds, etc; oilseeds such as peanuts.
-Condiments and spices, jaggery.
-Fruits such as sweet lime, mango, banana, chickoo, apricots, dates, figs, Melons, oranges, pears
-Brown sugar, coffee, cocoa powder, chocolate.
Fluids: The amount of fluids allowed usually depends on the urinary output and the body's need. Fluid allowance is different for each individual and has to be decided by the physician depending on the patients condition. Fluid intake and urinary output should be carefully recorded. Fluids include water, milk, curds, tea, coffee, sambhar, rasam and any other liquid food consumed.
Other minerals and vitamins: If a patient has abnormal levels of phosphate and calcium, phosphate intake should be restricted to prevent or slow down the imbalance between calcium and phosphorus in the blood. Since most of the food contain phosphorus, a phosphate binder is used to prevent its absorption. B-complex vitamins are beneficial and are generally supplemented along with vitamin C and iron.
POINTS TO REMEMBER:
- Calorie intake should be adequate in order to prevent tissue loss and also for protein build up. About 40-50cal/kg per day are sufficient.
- At least 50% of prescribed protein should be of high biological value and should be distributed in all the meals for better utilisation.
- Vegetables and pulses should be taken after leaching potassium.
- Low potassium fruits should be eaten once or twice a week.
- Salt should be restricted in case of oedema.
- Fluids should be restricted to the prescribed amounts.
- Spices and condiments should be used in small quantities.
- Foods high in sodium and potassium should be avoided.
- Rice products are much better tolerated than wheat. Therefore give riceflakes, items prepared out of rice flour, rice porridge, sago porridge, sago vada, sago khichdi, maida, arrowroot, sugar, boiled sweets, unsalted butter, unsalted margarine could be used. These foods have a very low content of sodium, potassium and protein but provide energy.
- Fruit juices, preservatives should be avoided.
- Methods that should be adopted for cooking are steaming, roasting, pressure cooking, stir frying, microwaving.
- Fruits recommended for patients are guava, apple, pineapple, papaya, pear.
20gm protein diet for a child weighing 20 kg.
Weight of the child approx 20kg
Protein (1gm/kg) = 20gm