Kidneys are a pair of bean-shaped organs that filter waste products, excess water, electrolytes and toxins from the blood. These excess products are then eliminated from the body in urine via the urethral system. Kidneys are also involved in red blood cell production; maintaining the water, electrolyte and acid-base balance; and regulating blood pressure.
Weakening of the kidney function, termed as kidney failure, renal failure or renal insufficiency, results in a condition in which the kidneys fail to adequately filter the metabolic waste from the blood. In addition, the ability of the kidneys to remove toxins and balance fluids is lost.
Renal failure is termed Acute Renal Failure, when the onset is sudden and kidneys shut down in a matter of days rather than weeks or months. The condition is usually a complication of other medical conditions or due to some types of rapidly progressing kidney conditions. Since it is always symptomatic and there is sudden deterioration of health, it needs to be recognized and treated immediately. Most often it is reversed when the primary condition is addressed. In a few cases, where there is a direct injury to the kidney, it may progress to chronic renal failure.
Chronic Renal Failure, on the other hand is a more insidious and gradual deterioration of the kidney function. It results in a gradual decrease in urine production and a build-up of metabolic waste products and toxins in the blood. Many conditions lead to chronic kidney failure, chief of which are uncontrolled diabetes and hypertension (high BP). Other common conditions are immune-related injury to kidneys, drug side effects, exposure to certain industrial toxins and environmental pollutants, and conditions that decrease blood supply to kidneys or obstruct the flow of urine from the kidneys.
Chronic Renal Failure, also termed Chronic Kidney Disease (CKD) is diagnosed by estimating the glomerular filtration rate (GFR). GFR is estimated using a formula which takes into account age, weight and serum level of a substance called creatinine. It is classified into stages 1 to 5 based on the GFR. Stage 4 & 5 are called End-Stage Renal Disease (ESRD). People with ESRD require renal replacement therapy either via dialysis or transplant to survive.
Since the ability to clear metabolic waste is compromised and water and electrolyte balance is impaired, those with CKD should pay attention to their diet to maintain kidney health, prevent bone loss, reduce complications and avoid serious electrolyte disturbances. This special diet is generally known as a Renal Diet.
A renal diet is low in sodium, phosphorous, and protein. It promotes the importance of consuming high-quality protein and limits fluid intake. Potassium and calcium intake must also be limited in certain patients based on a stage of CKD and accompanying conditions.
Protein breakdown creates by-products that are filtered by the kidneys. When there is renal failure, the kidneys fail to remove protein waste which then accumulates in the blood. Thus, patients with CKD are often recommended a low-protein diet based on weight, stage of the disease, muscle tone, etc. However, if the patient is on dialysis, then more protein is required. The recommended sources of high-quality protein for CKD are fish, poultry, and eggs.
Salt or Sodium
Sodium, a naturally occurring mineral is a component of most foods we eat. Common salt is a compound of sodium and chloride. Being one of the body’s major electrolytes, sodium helps in regulating nerve function and muscle contraction, regulating blood pressure, maintaining acid-base balance in the blood, and balancing how much water is kept in the body and how much is eliminated.
The kidneys tightly regulate the amount of sodium in the body along with the water level. In CKD, one cannot eliminate excess sodium and fluids from the body. This can lead to shortness of breath caused by fluid build-up in the lungs, edema: swelling in the hands, legs and face, increased thirst, heart failure, and high blood pressure.
Sodium intake needs to be monitored in CKD. It can be done by taking a few steps like reading the label of foods for the portion of sodium, keeping a watch over the serving size, using spices that do not have “salt” in it, consuming fresh produce and fruits without adding salt, avoiding salt added canned and frozen food, and limiting sodium intake to 400 mg per meal and 150 mg per snack.
Potassium is found in the body and in many foods we consume. The muscles work correctly and heartbeats properly when the right amount of potassium is consumed. The kidneys help to keep the right amount of potassium in the body and eliminate excess potassium during urination. Abnormal increase in potassium levels may lead to irregular heart rhythms, muscle weakness, slow pulse, and heart attack and may also cause death.
When the kidneys fail to eliminate potassium, it should naturally be monitored closely. Foods that are rich in potassium include avocado, banana, potatoes, spinach, citrus juices, fish, etc. Limit milk and dairy products to 8 Oz. per day, and pay attention to serving size and read the labels properly before purchasing.
Calcium and Phosphorus
Formation and maintenance of bones require the minerals calcium and phosphorus. They also aid in muscle movement and development of the connective tissue of the muscles. The small intestines absorb phosphorus when food is consumed, and it is stored in the bones. Excess phosphorus is eliminated by the kidneys. If phosphorus levels increase, as in CKD, it lowers serum calcium levels, which in turn causes the body to pull out calcium from the bones, thereby making them weak. It also leads to dangerous calcium deposits in lungs, heart, eyes and lungs.
It is important to manage phosphorus levels properly in CKD. Foods rich in this mineral include meat, fast food, cheese, seeds, milk, cola, and canned fish. Fruit sources include apples, pineapples, plums, berries, cherries, pears, grapes, peaches. Vegetable sources include cabbage, broccoli, carrots, cauliflowers, celery, cucumber, eggplant, lettuce, onion, pepper, watercress.
In the early stages of CKD, limiting fluid may not be required, but in the later stages, it is vital because normal fluid consumption may cause fluid build-up in the body. This can be quite dangerous as it may lead to fluid accumulation in the lungs and heart failure. To have a control on fluid in-take, patients should not drink more than the recommended amount of fluids, avoid salty foods, count all the foods that will melt at room temperature as fluids (like popsicles and ice creams), reduce intake of fruit and vegetables with high water content like grapes, melons, lettuce, tomatoes and celery.
If you suffering from CKD or on dialysis, it is important for you to be aware of the above and to follow the renal diet guidelines strictly. Please consult your nephrologist or dietician about specific recommendations based on your current condition and metabolic requirements.