The major role of the kidneys is to remove waste products and purify blood. Besides this, the kidney plays an important role in removing extra water, minerals and chemicals; it also regulates water and minerals like sodium, potassium, calcium, phosphorus and bicarbonate in the body.
In patients suffering from chronic kidney disease (CKD), regulation of fluids and electrolytes may be deranged. Because of this reason even normal intake of water, common salt or potassium can cause serious disturbances in fluid and electrolyte balance.
To reduce the burden on the kidney with impaired function and to avoid disturbances in fluid and electrolyte balance, patients with chronic kidney disease should modify their diet as per the guidance of the doctor and the dietitian. There is no fixed diet for CKD patients. Each patient is given a different dietary advice depending on clinical status, the stage of kidney failure and other medical problems. Dietary advice needs to be altered for the same patient at different times.
Goals of dietary therapy in CKD patients
- Slow down the progression of chronic kidney disease and to postpone the need for dialysis.
- Reduce the toxic effects of excess urea in the blood.
- Maintain optimal nutritional status and prevent the loss of lean body mass.
- Reduce the risk of fluid and electrolyte disturbances.
- Reduce the risk of cardiovascular disease.
General principles of dietary therapy in CKD patients
- Restrict protein intake to <0.8 gm/kg of body weight/day for patients not on dialysis. Patients already on dialysis require an increased amount of protein (1.0 -1.2 gm/kg body weight/day) to replace protein that may be lost during the procedure.
- Supply adequate carbohydrates to provide energy.
- Supply a moderate amount of fats. Cut down the intake of butter, ghee and oil.
- Limit the intake of fluid and water in case of swelling (edema).
- Restrict the amount of sodium, potassium and phosphorus in the diet.
- Supply vitamins and trace elements in adequate amounts. A high fiber diet is recommended.
Details of selection and modification in diet of patients with CKD
High Calorie Intake
The body needs calories for daily activities and to maintain temperature, growth and adequate body weight. Calories are supplied chiefly by carbohydrates and fats. The usual caloric requirement of CKD patients is 35 - 40 kcal/kg body weight per day. If caloric intake is inadequate, the body utilizes protein to provide calories. This breakdown of protein can lead to harmful effects such as malnutrition and a greater production of waste products. It is thus essential to provide an adequate amount of calories to CKD patients. It is important to calculate the caloric requirement according to a patient’s ideal body weight, and not current weight.
Carbohydrates are the primary source of calories for the body. Carbohydrates are found in wheat, cereals, rice, potatoes, fruits and vegetables, sugar, honey, cookies, cakes, sweets and drinks. Diabetics and obese patients need to limit the amount of carbohydrates. It is best to use complex carbohydrates from cereals like whole wheat and unpolished rice which would also provide fiber. These should form a large portion of the carbohydrates in the diet. All other simple sugar containing substances should form not more than 20% of the total carbohydrate intake, especially in diabetic patients. Non-diabetic patients may replace calories from protein with carbohydrates in the form of fruits, pies, cakes, cookies, jelly or honey as long as desserts with chocolate, nuts, or bananas are limited.
Fats are an important source of calories for the body and provide two times more calories than carbohydrates or proteins. Unsaturated or “good” fats like olive oil, peanut oil, canola oil, safflower oil, sunflower oil, fish and nuts are better than saturated or “bad” fats such as red meat, poultry, whole milk, butter, ghee, cheese, coconut and lard. Patients with CKD should reduce their intake of saturated fats and cholesterol, as these can cause heart disease.
Among the unsaturated fats it is important to pay attention to the proportion of monounsaturated and polyunsaturated fats. Excessive amounts of omega-6 polyunsaturated fatty acids (PUFA) and a very high omega-6/omega-3 ratio is harmful while low omega-6/omega-3 ratio exerts beneficial effects. Mixtures of vegetable oil rather than single oil usage will achieve this purpose. Trans fat containing substances like potato chips, doughnuts, commercially prepared cookies and cakes are potentially harmful and should be avoided.
Restrict Protein Intake
Protein is essential for the repair and maintenance of body tissues. It also helps in healing of wounds and fighting against infection. Protein restriction (< 0.8 gm/kg body weight/day) is recommended for CKD patients not on dialysis to reduce the rate of decline in kidney function and delay the need for dialysis and kidney transplantation. Severe protein restriction should be avoided however because of the risk of malnutrition. Poor appetite is common in CKD patients. Poor appetite and strict protein restriction together can lead to poor nutrition, weight loss, lack of energy and reduction in body resistance, which increase the risk of death. Proteins with high biologic value such as animal protein (meat, poultry and fish), eggs and tofu are preferred. High-protein diets (e.g. Atkins diet) should be avoided in CKD patients. Likewise, the use of protein supplements and drugs such as creatine used for muscle development are best avoided unless approved by a physician or dietitian. However, once a patient is on dialysis, protein intake should be increased to 1.0 – 1.2 gm/kg body weight/day to replace the proteins lost during the procedure.
Why must patients with CKD take precautions regarding fluid intake?
The kidneys play a major role in maintaining the proper amount of water in the body by removing excess fluid as urine. In patients with CKD, as the kidney function worsens, the volume of urine usually decreases. Reduced urine output leads to fluid retention in the body causing puffiness of the face, swelling of the legs and hands and high blood pressure. Accumulation of fluid in the lungs (a condition called pulmonary congestion or edema) causes shortness of breath and difficulty in breathing. If this is not controlled, it can be life threatening.
What are the clues that suggest excess water in the body?
Excess water in the body is called fluid overload. Leg swelling (edema), ascites (accumulation of fluid in the abdominal cavity), shortness of breath, and weight gain in a short period are the clues that suggest fluid overload.
What precautions must CKD patients take to control fluid intake?
To avoid fluid overload or deficit, the volume of fluid should be recorded and followed as per the recommendation of the doctor. The volume o fluid permitted may vary for each CKD patient and is calculated on the basis of urine output and fluid status of each patient.
How much fluid is a chronic kidney disease patient advised to take?
- In patients without edema and with adequate urine output unrestricted water and fluid intake is permitted. It is a common misconception that patients with kidney disease should take large amounts of fluid to protect the kidney. The amount of fluid allowed is dependent on the clinical status and kidney function of the patient
- Patients with edema and reduced urine output are instructed to restrict fluid intake. To reduce swelling, fluid intake in 24hours should be less than the volume of urine produced per day.
- In order to avoid fluid overload or deficit in patients without edema the allowable volume of fluid per day = urine volume of previous day plus 500 ml. The additional 500 ml of fluid approximately make up for the fluids lost through perspiration and breathing.
Why must CKD patients maintain a record of their daily weights?
Patients should keep a record of their daily weight to monitor fluid volume in the body and to detect fluid gain or loss. The body weigh remains constant when the instructions regarding fluid intake are followed strictly. Sudden weight gain indicates fluid overload due to increase in fluid intake. Weight gain warns the patients about the need for more meticulous fluid restriction. Weight loss usually occurs as a combined effect of restriction of fluid and a response to diuretics.
Useful Tips to Reduce Fluid Intake
It is difficult to restrict fluid intake, but these tips will help you:
- Weigh yourself at the same time every day and adjust fluid intake accordingly.
- The doctor advises you on how much fluid consumption is permitted in a day. Calculate accordingly and take the measured volume of fluid everyday. Remember that fluid intake includes not only water but also tea, coffee, milk, juice, ice cream, cold drinks, soup, and other foods with a high water content such as watermelon, grapes, lettuce, tomatoes, celery, gravy, gelatin, and frozen treats like popsicles.
- Reduce salty, spicy and fried food in your diet as they increase thirst, leading to a greater consumption of fluids.
- Drink only when you are thirsty. Do not drink as a habit or because everyone is drinking.
- When you are thirsty, take only a small amount of water or try ice. Take a small ice cube and suck it. Ice stays longer in the mouth than liquid, so it is more satisfying than the same amount of water. Do not forget to account for ice as consumed fluid. For easy calculation, freeze the allotted amount of water into an ice tray.
- To take care of dryness of the mouth, one can gargle with water without drinking it. Dryness of mouth can be reduced by chewing gums, sucking hard candy, lemon wedge or mints and the use of mouthwash to moisten the mouth.
- Always use a small sized cup and glass for your beverages to limit fluid intake.
- Take medicines after meals when you are taking water to avoid extra water consumption for medicine.
- A patient must keep himself busy with work. A patient who has little to occupy himself feels the desire to drink water more often.
- High blood sugar in diabetic patients can increase thirst. A stringent control of blood sugar is essential to reduce thirst.
- Since hot weather increases one’s thirst, any measure taken to live in cooler comfort is desirable and recommended.
How does one measure and consume the prescribed amount of fluid per day?
- Fill a container with water, equal to the exact amount of fluid prescribed by the doctor for daily intake.
- The patient must bear in mind that no more than that amount of fluid intake is permitted for the day.
- Each time the patient consumes a certain amount of fluid, the same amount of water should be removed from the water container and discarded.
- When the container has no more water, the patient will have consumed his quota of fluid for the day and should not drink anymore.
- It is advisable to distribute total fluid intake evenly throughout the day to avoid the need for additional fluid.
- Repeated daily, this method, if followed, effectively delivers the prescribed amount of fluid per day and prevents excessive fluid intake.
Salt (Sodium) Restriction in Diet
Why is a low sodium diet advised for patients with CKD?
Sodium in our diet is important for the body to maintain blood volume and to control blood pressure. Our kidneys play an important role in the regulation of sodium. In patients with CKD, the kidneys cannot remove excess sodium and fluid from the body so sodium and water build up in the body. An increased amount of sodium in the body leads to increased thirst, swelling, shortness of breath and increase in blood pressure. To prevent or reduce these problems, patients with CKD must restrict sodium intake in their diet.
What is the difference between sodium and salt?
The words sodium and salt are commonly used as synonyms. Common salt (table salt) is sodium chloride and contains 40% sodium. Salt is the principle source of sodium in our diet. But salt is not the only source of sodium. There are quite a few other sodium compounds in our food, such as:
- Sodium alginate: Used in ice-cream and chocolate milk
- Sodium bicarbonate: Used as baking powder and soda
- Sodium benzoate: Used as a preservative in sauce
- Sodium citrate: Used to enhance flavor of gelatin, desserts and beverages
- Sodium nitrate: Used in preserving and coloring processed meat
- Sodium saccharide: Used as artificial sweetener
- Sodium sulfite: Used to prevent discoloration of dried fruits The above mentioned compounds contain sodium but are not salty in taste. Sodium is hidden in these compounds.
How much salt should one take?
A typical daily intake of salt is about 10 to 15 grams (4-6 grams of sodium) per day. Patients with CKD should take salt according to the recommendation of the doctor. CKD patients with edema (swelling) and high blood pressure are usually advised to take less than 2 grams of sodium per day.
Which foods contain high amounts of sodium?
Foods high in sodium include:
- Table salt (common salt), baking powder
- Processed foods like canned foods, fast foods and “deli” meats3. Readymade sauces
- Seasonings and condiments such as fish sauce and soy sauce
- Baked food items like biscuits, cakes, pizza and breads
- Wafers, chips, popcorn, salted groundnuts, salted dry fruits like cashew nuts and pistachios
- Commercial salted butter and cheese
- Instant foods like noodles, spaghetti, macaroni, and cornflakes
- Vegetables like cabbage, cauliflower, spinach, radish, beetroot, and coriander leaves
- Coconut water
- Drugs like sodium bicarbonate tablets, antacids, laxatives
- Non-vegetarian foods like meat, chicken, and animal innards like kidneys, liver and brain
- Seafoods like crab, lobster, oyster , shrimp, oily fish and dried fish
Practical Tips to Reduce Sodium in Food
- Restrict salt intake and avoid extra salt and baking soda in diet. Cook food without salt and add permitted amounts of salt separately. This is the best option to reduce salt intake and ensure consumption of the prescribed amount of salt in everyday diet.
- Avoid foods with high sodium content (as listed above).
- Do not serve salt and salty seasonings at the table or altogether remove the salt shaker from the dining table.
- Carefully read labels of commercially available packaged and processed foods. Look not only for salt but also for other sodium containing compounds. Carefully check the labels and choose “sodium-free” or “low-sodium” food products. Make sure however that potassium is not used to substitute sodium in these foods.
- Check sodium content of medications.
- Boil vegetables with high sodium content. Throw away the water. This can reduce sodium content in vegetables.
- To make a low salt diet tasty, one can add other spices and condiments such as garlic, onion, lemon juice, bay leaf, tamarind pulp, vinegar, cinnamon, cloves, nutmeg, black pepper, and cumin.
- Caution! Avoid the use of salt substitutes as they contain high amounts of potassium. High potassium content of salt substitutes can raise the potassium levels in blood to dangerous levels in CKD patients.
- Do not drink softened water. In the process of water softening, calcium is replaced by sodium. Water purified by reverse osmosis process is low in all minerals including sodium.
- While eating at restaurants, select foods that contain less sodium.
Potassium Restriction in Diet
Why are CKD patients advised to restrict potassium in diet?
Potassium is an important mineral in the body that is needed for the proper functioning of muscles and nerves and to keep the heart beat regular. Normally, the level of potassium in body is balanced by eating potassium containing foods and removal of excess potassium in the urine. Removal of excess potassium in the urine may be inadequate in a patient with chronic kidney disease and can lead to the accumulation of a high level of potassium in the blood (a condition known as hyperkalemia). The risk of hyperkalemia is less in patients undergoing peritoneal dialysis compared to those on hemodialysis. The risk differs in both groups because the process of dialysis is continuous in peritoneal dialysis while it is intermittent in hemodialysis.
High potassium levels can cause severe muscle weakness or an irregular heart rhythm that can be dangerous. When potassium is very high, the heart can stop beating unexpectedly and cause sudden death. High potassium levels can be life threatening without noticeable manifestations or symptoms (and therefore it is known as a silent killer).
To avoid serious consequences of high potassium, CKD patients are advised to restrict potassium in diet.
What is normal potassium level in blood? When is it considered high?
The normal serum potassium (level of potassium in blood) is 3.5 mEq/L to 5.0 mEq/L.
When the serum potassium is 5.0 to 6.0 mEq/L, dietary potassium needs to be limited.
When the serum potassium is greater than 6.0 mEq/L, active medical intervention is needed to reduce it.
A serum potassium greater than 7.0 mEq/L is life threatening and needs urgent treatment such as emergency dialysis.
Classification of food according to potassium content:
To maintain proper control of potassium in blood, food intake must be modified as per the doctor’s advice. On the basis of potassium contents, foods are classified into three different groups (high, medium, and low potassium containing foods).
High potassium = More than 200 mg/ 100 gms of food
Medium potassium = 100 to 200 mg/ 100 gms of food
Low potassium = Less than 100 mg/ 100 gms of food
Foods with high potassium content
- Fruits: Fresh apricot, ripe banana, chico, fresh coconut, custard apple, gooseberry, guava, kiwi fruit, ripe mango, oranges, papaya, peach, pomegranate and plum
- Vegetables: Broccoli, cluster beans, coriander, drumstick, mushroom, raw papaya, potato, pumpkin, spinach, sweet potato, tomatoes and yam
- Dry fruits: Almond, cashew nut, dates, dry figs, raisins and walnut
- Cereals: wheat flour
- Legumes: Red and black beans and mung (monggo) beans
- Non-vegetarian food: Fish like anchovy and mackerel; shell fish like prawns, lobster and crabs; and beef
- Drinks: Coconut water, condensed milk, buffalo milk, cow milk, chocolate drinks, fresh fruit juices, soup, beer, wine and many aerated drinks
- Miscellaneous: Chocolate, chocolate cake, chocolate ice cream, Lona salt (salt substitute), potato chips and tomato sauce
Foods with Medium Potassium Content
- Fruits : ripe cherries, grapes, lychees, pear, sweet lime and watermelon
- Vegetables: Beet root, raw banana, bitter gourd, cabbage, carrot, celery, cauliflower, French beans, okra (ladies finger), raw mango, onion, radish, green peas, sweet corn and safflower leaves
- Cereals: Barley, general purpose flour, noodles made from wheat flour, rice flakes (pressed rice) and wheat vermicelli
- Legumes: red and black beans and mung (monggo) beans
- Non-vegetarian food: Liver
- Drinks: curd
Foods with Low Potassium Content
- Fruits : Apple, blackberries, lemon, pineapple and strawberries
- Vegetables : Bottle gourd, broad beans, capsicum, cucumber, garlic, lettuce, green peas, raw mango and pointed gourd
- Cereals : Rice, rava and wheat semolina
- Legumes : Green peas
- Non-vegetarian food : Beef, lamb, pork, chicken and egg
- Drinks : Coca-cola, coffee, lemonade, lime juice in water, and soda
- Miscellaneous : Cloves, dried ginger, honey, mint leaves, mustard, nutmeg, black pepper and vinegar
Practical Tips to Reduce Potassium in Food
- Take one fruit per day, preferably with low potassium.
- Take one cup of tea or coffee per day.
- Vegetables with potassium should be taken after reducing the amount of potassium (as mentioned below).
- Avoid coconut water, fruit juices and foods with high potassium contents (as listed above).
- Almost all food contains some potassium, so the key is to choose foods with a low potassium content when possible.
- Restriction of potassium is necessary not only for predialysis CKD patients, but is also necessary even after initiating dialysis.
How does one reduce potassium content in vegetables?
- Peel and cut vegetables into small pieces.
- Wash vegetables with lukewarm water and put them in a large pot.
- Fill the pot with hot water (the quantity of water must be four to five times the volume of vegetables) and soak the vegetables for at least one hour.
- After soaking the vegetables for 2 - 3 hours, rinse them three times with warm water.
- Subsequently boil the vegetables with extra water. Discard the water.
- Cook the boiled vegetables as desired.
- Although you can reduce the amount of potassium in vegetables, it is still preferable to avoid high potassium containing vegetables or take them in small quantities.
- As vitamins are lost in cooked vegetables, vitamin supplements should be taken as per the doctor’s advice.
Special tips for leaching potassium from potatoes
- Dicing, slicing or grating potatoes into smaller pieces is important. Maximizing the surface of the potatoes exposed to water by this method helps increase potassium loss from the potatoes.
- The temperature of the water used to either soak or boil the potatoes makes the difference.
- Using large amounts of water to soak or boil potatoes is helpful.
Phosphorus Restriction in Diet
Why must CKD patients take a low phosphorus diet?
- Phosphorus is a mineral essential to keep bones strong and healthy. Excess phosphorus present in food is removed from the body by urine excretion. This maintains blood phosphorus levels.
- The normal value of phosphorus in blood is 4.0 to 5.5 mg/dl.
- Patients with CKD cannot eliminate the extra phosphorus taken in food so the blood level rises. This increased phosphorus drains out calcium from the bones making them weak.
- Increase in phosphorus level can lead to many problems like itching, weakness of muscles and bones, bone pains, bone stiffness and joint pains. The stiffness of bone results in increased susceptibility to fracture.
What foods containing high phosphorus should be reduced or avoided?
Foods containing high phosphorous include:
- Milk and dairy products: cheese, chocolate, condensed milk, ice cream, milk shake.
- Dry fruits: cashew nuts, almonds, pistachios, dry coconut, walnuts.
- Cold drinks: dark colas, beer.
- Carrot, corn, groundnut, fresh peas, sweet potato.
- Animal protein: meats, chicken, fish and egg.
High Vitamin and Fiber Intake
CKD patients generally suffer from an inadequate supply of vitamins during the predialysis period due to poor appetite, and an overly restricted diet in the attempt to delay progression of renal disease. Certain vitamins – especially water soluble vitamins B, vitamin C and folic acid – are lost during dialysis.
To compensate for inadequate intake or loss of these vitamins, CKD patients usually need supplementation of water-soluble vitamins and trace elements. High fiber intake is beneficial in CKD. Patients are therefore advised to take more fresh vegetables and fruits rich in vitamin and fibers while avoiding those with high potassium content.
Designing the Daily Food
For CKD patients daily food intake and water intake are planned and charted out by the dietitian in accordance with the advice of the nephrologist.
Common principles for the diet plan
- Water and liquid food intake:Fluid intake should be restricted according to the doctor’s advice. Daily weight chart must be maintained. Any inappropriate gain in weight may indicate increased fluid intake.
- Carbohydrate: To ensure that the body gets adequate calories, the CKD patient can take sugar or glucose containing food along with cereals provided he/she is not diabetic.
- Protein: Lean meat, milk, cereals, legumes, eggs and chicken are the main sources of protein. CKD patients who are not on dialysis are advised to limit dietary protein to < 0.8 grams/kg body weight/day. Once dialysis is started, dietary intake can be increased to 1-1.2 grams/kg body weight/day. Patients undergoing peritoneal dialysis may need dietary proteins as high as 1.5 grams/kg body weight per day. While animal proteins contain all essential amino acids (hence are called complete proteins or proteins with high biologic value) and would be ideal, they should be limited especially in patients not yet on dialysis because they may accelerate the progression of CKD.
- Fat: Fats may be taken in as an energy source since they are a good source of calories. Monounsaturated and polyunsaturated fats in the form of olive oil, safflower oil, canola oil or soybean oil may be taken in limited quantities. Avoid saturated fats such as those found in animal lards.
- Salt: Most patients are advised to take a low salt diet. It is good to observe a “no added salt” diet. Look at food labels and go for low sodium foods but make sure that salt substitutes containing high amounts of potassium are also avoided. Check food labels for other foods containing sodium such as sodium bicarbonate (baking powder) and avoid them.
- Cereals: Rice or rice products like flattened rice can be taken. To avoid monotony of taste one can rotate intake of various cereals like wheat, rice, sago, semolina, all purpose flour, and cornflakes. Small quantities of corn and barley can be taken.
- Vegetables: Vegetables with low potassium can be liberally taken. But vegetables with high potassium must be processed to remove potassium before consumption. To improve taste, lemon juice can be added.
- Fruits: Fruits with low potassium content like apple, grapes and berry can be taken but only once a day. On the day of dialysis , patients can take any one fruit. Fruit juice and coconut water must be avoided.
- Milk and milk products: Milk and milk products such as milk, yogurt and cheese contain large amounts of phosphorus and need to be limited. Other dairy foods that have lower amounts of phosphorus include butter, cream cheese, ricotta cheese, sherbets and nondairy whipped toppings may be taken instead.
- Cold drinks: Avoid dark colored sodas as they have a high phosphorus content. Do not take fruit juice or coconut water because of the potentially high potassium content.
- Dry fruits: Dry fruits, groundnut, sesame seeds, fresh or dry coconut must be avoided.
Source: Kidney Education Foundation