Nutrition plays a significant role in kidney disease, but there is no single kidney diet. Your specific nutrition therapy will depend on the diagnosis you receive from your nephrologist: nephrotic syndrome, acute kidney injury, chronic kidney disease (stages 1–4) end stage kidney disease, and whether you will be on dialysis or preparing for a kidney transplant. Some dietary guidelines are aimed at managing the underlying cause of kidney disease such as diabetes or hypertension.
Your nephrologist will discuss the role of nutrition in your diagnosis and prescribe a specific diet or refer you to a registered dietitian who will work with you to create specific meal plans and educate about the various food that will be in your new meal plans, and how to shop and dine on your new diet.
The diets may involve controlling the amount of sodium, potassium, phosphorus, protein, and fluid that you ingest. People with kidney disease who have been prescribed dialysis treatment should be in consultation with a renal dietitian at the dialysis unit.
Sodium is a mineral found in many foods and is important to many different bodily functions. One of the most important functions of sodium involves maintaining fluid levels. If too much sodium builds up in the body it causes thirst and fluid buildup. Normally functioning kidneys help to maintain proper levels of sodium in the body. If the kidneys begin to fail however, it becomes more important to maintain appropriate levels of sodium intake.
The easiest way to avoid excess sodium intake is to eliminate putting extra salt on foods. People frequently add salt during cooking and at the table. Even just topping these behaviors will usually cut back significantly on the amount of sodium ingested. It is also important to avoid particularly salty foods such as theater popcorn, potato chips, salted pretzels, bacon and other cured meats, and processed cheese. Checking the ingredients list of processed, frozen, and canned foods is a good way to see how much sodium the product contains. Canned soups are often surprisingly high in salt, but often times there are low-sodium alternatives available.
Potassium is a mineral found in varying amounts in almost all foods, including fruits, vegetables, meat, and dairy products. The body uses potassium for a variety of important functions such as maintaining fluid and electrolyte balance, sending nerve impulse to muscles, and aiding in metabolic processes. When a person’s kidneys are functioning normally they filter out excess potassium, helping to maintain the proper amount in the body. Without properly functioning kidneys, patients need to control their potassium intake.
Avoiding foods with high levels of potassium, while maintaining a healthy diet, can be quite difficult because many fruits and vegetables are high in potassium. Oranges, broccoli, tomatoes, potatoes, and carrots are all high in potassium. Apples, blueberries, grapes, strawberries, lettuce, and onions are all relatively low in potassium. Canned vegetables and the juices they are usually canned are particularly high in potassium. For patients with kidney problems who want to eat certain high potassium vegetables, there is one method for removing some of the potassium, called leaching. This process varies depending on the vegetable, but generally it involves repeatedly rinsing and boiling the vegetable in a large amount of water.
Phosphorus is another mineral found in many foods. The body must maintain a proper balance of phosphorus and calcium in order to build and preserve healthy bones. Normally, the kidneys help to maintain this balance by removing excess phosphorus from the bloodstream. However, patients with kidney disease may need to take steps to maintain this balance by watching what they eat, because their kidneys are no longer able to do this important job. If too much phosphorus builds up in the body it can pull calcium out of the bones, making them weak and easily breakable.
People following a kidney diet may be told to avoid foods that are high in phosphorus, such as beer, soda, cheese, milk, yogurt, oysters, beans, peas, nuts, and many whole grain products. A renal dietician may also prescribe a phosphate binder, which can help control the amount of phosphate that the body absorbs.
Proteins are complex organic molecules made of amino acid chains. The body uses these chains to build and maintain muscles, organs, and glands. When the body breaks down protein it produces a waste product called urea. This waste product is usually filtered out by the kidneys and expelled from the body in urine. Patients experiencing kidney failure must be careful about the amount and type of protein they consume because the kidneys are no longer doing a good job of removing urea. If too much urea builds up in the body it can cause serious illness. Patients must be sure to get enough protein however, because without protein the body is not able to perform proper muscle maintenance.
When patients are experiencing kidney failure, their kidneys are no longer removing water from the body with proper efficiency. The worse that the kidneys are functioning, the more important it is for patients to monitor their fluid intake. Water retention can cause swelling in the feet and ankles, as well as other parts of the body.
The function of the kidney diet is to help patients with kidney disease to feel better, limit their symptoms, and slow the development of kidney failure. For people with kidney disease, it is important to maintain the proper balance of electrolytes, minerals, and fluid in the bloodstream. For patients undergoing dialysis treatments, this becomes even more important. This is because the kidneys work to rid the body of excess electrolytes, minerals, and fluid by filtering the blood. When a person’s kidneys are not functioning properly, these substances can build up in the body and cause symptoms such as nausea, vomiting, tiredness, weakness, sleepiness, and other problems. If patients lower their intake of certain substances they can help to control these problems, but if they limit these same substances too severely, they can suffer from malnutrition. Kidney diets are designed to help patients find the best balance for their body.
A concern for kidney patients is that they maintain proper protein levels. Kidneys, when functioning normally, remove urea, a waste product of protein, from the bloodstream. When kidneys are not functioning properly, urea can build up in the system and make patients ill. Because of this patients with kidney failure need to limit the amount of protein in their diets. However, it is important for patients to not be over-zealous in their limiting of protein, because too getting too little protein can also have serious health consequences.
Patients with kidney disease also run the risk of losing bone calcium due to high phosphorus levels. If patients do not take a phosphate binder, phosphorus in the blood will pull calcium from the bones, making them weak and brittle.
Potassium levels are also important to people with kidney disease. This mineral affects the steadiness of the heartbeat and its level in the bloodstream is normally kept steady by the kidneys. If there is too much potassium in the blood it can be very dangerous for the heart, and possibly even fatal.
Maintaining daily calorie intake is a concern for patients following a kidney diet. With the great number of restrictions placed on the kinds of foods a person can eat it can be difficult for a patient to eat enough calories each day. However if overall caloric intake is not maintained at high enough levels the patient can suffer body tissue breakdown.
If patients with later stages of kidney disease do not pay close attention to their sodium and fluid intake they have a serious risk of retaining water. Fluid can build up and cause painful swelling and weight gain. It also can cause blood pressure to rise which can adversely affect the heart. Kidney disease patients also have a greater risk of heart disease. Following a low-fat diet will usually be necessary.