Basic nutritional principles in chronic kidney disease
The kidneys are the body’s natural “filter” seeing as they help remove toxins and excess water from our blood. They filter approximately 200 liters of blood daily and dispose of many substances, such as medications, through the urine. In kidney patients, the kidneys are not able to fully perform this task, which results in an imbalance of elements in the blood.
For this reason, diet constitutes a key part of the treatment of patients with chronic kidney disease, both before reaching the final stage and during renal replacement therapy. Proper nutrition helps reduce uremic toxins and metabolic waste; it delays the progression of the disease and improves quality of life. The nutritional needs of each patient vary; however, the albumin content of the food always plays a dominant role. Moreover, it is considered necessary for their daily diet to maintain a balance in minerals, fluids, and electrolytes. Especially for patients undergoing dialysis, a specific diet should be followed to avoid malnourishment and malnutrition. At the same time, a special diet can also significantly help in cases of chronic kidney disease by focusing on a reduced intake of fluids, proteins, sodium, potassium, and phosphorus.
The general guideline in regard to the fluid intake of kidney patients is that the less urine they excrete the less fluid they need to drink. Large amounts of fluid can be dangerous because any excess could increase blood pressure and potentially lead to pulmonary edema and heart failure.
One of the most important dietary guidelines for patients with chronic kidney disease is proper protein and energy intake. Moderate protein intake is recommended, because kidney patients accumulate significant amounts of urea in their blood as they cannot excrete it through the urine. The main sources of protein are meat, poultry, fish, eggs, dairy products, and legumes. The recommended protein intake for hemodialysis patients is 1.2 g of protein / kg of body weight / day, and 1.2 - 1.3 g of protein / kg of body weight / day for patients undergoing peritoneal dialysis.
Sodium intake should also be restricted. However, this should not only include the reduction the amount of salt used during meal preparation. The reason for this is that approximately 85% of the sodium we consume is hidden in other foods and only 15% is found in salt. Some foods that contain larger amounts of sodium are the following: bread, standardized cheeses, salted nuts, frozen products, breakfast cereals, and canned foods.
Normal kidneys can excrete excess sodium through the urine to maintain the necessary balance, but in the case of kidney patients the total daily salt intake should be limited. They should also pay attention to the natural salt content of certain foods. Foods rich in salt increase thirst and fluid intake is recommended when urine volume is reduced to 500-750 ml.
In addition, another parameter that should be taken into account is the patients’ potassium intake. Potassium is one of the elements that need to be limited in their diet. Normal kidneys can excrete excess potassium, but this function is impeded in kidney patients. Therefore, potassium cannot be easily disposed of, leading to the development of hyperkalemia (increased amount of potassium in the blood), which can in turn cause muscle weakness and severe arrhythmias. Potassium is found in most foods, with fruits and vegetables being the main sources.
Phosphorus intake should also be decreased in the diet of kidney patients, as renal dysfunction leads to defective phosphorus excretion and increased serum levels in the blood. Larger amounts of phosphorus are found in dairy products, eggs, and meat. Lastly, because the intake of certain food groups is usually limited, the attending physician of each patient will usually recommend that they take vitamin D and iron supplements to meet the body’s needs for valuable vitamins and minerals.
Kalliopi Retsa, Scientific Director at the Mesogeios Dialysis Center of Chalkida
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