Diet for Kidney Failure

Diet and kidney health

The kidneys (two) are organs dedicated to the filtration (or purification) of the blood, therefore they are essential for the life of man. In order to guarantee their integrity, it is advisable to recognize and remove the etiological agents that can compromise them; among these: drug abuse, inappropriate dietary behaviors, alcoholism, sports doping, drug addiction, infections, hypertension, diabetes, impairment of other organs, etc.

Diet plays a key role in maintaining kidney health; in fact, the waste of ALL the nutritional molecules previously digested-absorbed-metabolized, are filtered by the bloodstream thanks to the kidney, then collected in the bladder and expelled with the urine through urination. The diet that guarantees good renal functioning must be normocaloric and correctly distributed (see LARN - Recommended Nutrient Intake Levels for the Italian population).

Disorders and renal failure

Kidney disorders are different and require special treatments; following the nephrological medical diagnosis, the nutrition professional intervenes on the subject's nutritional regime based on the metabolic needs that the specific disorder imposes.

1. Nephritic syndrome: nephritic syndrome is defined as an inflammatory process (mostly transient) caused by the toxic action of some bacteria (usually staphylococci). Nephritic syndrome is characterized by the reduction of the glomerular filtrate (the glomerulus is the vascular of the nephron) and for the "progressive renal failure; moreover, they significantly increase water retention and sodium (Na) retention. The diet for renal insufficiency of the nephritic type must absolutely provide a MINIMUM and indispensable supply of proteins; the catabolism of amino acids (especially aromatics) worsens the nitrogen balance by significantly altering the composition of the blood. Furthermore, given the reduced filtration capacity, it is also advisable to reduce the dietary content of electrolytes and water. At the same time, it is necessary to guarantee the right energy intake and constantly monitor the blood parameters; in case of acute renal failure, it is essential to "hemodialysis, a therapy that replaces kidney function.
2. Nephrotic syndrome: nephrotic syndrome can express both a primary glomerular pathology and other systemic disorders; it is characterized by the urinary protein excretion which, in the long term, it causes hypoproteidemia (reduced presence of proteins in the blood) and reduction of tissue protein quantity. Diet in nephrotic syndrome aims at the control of hypertension through the reduction of dietary sodium, and in parallel keeps the protein content constant in order to buffer the hypoproteidemia induced by abundant urinary losses; the reduction of sodium and the maintenance of the right concentration of plasma proteins prevent the onset of hypertension and blood hypo-osmolarity, preventing the formation of interstitial edema (accumulation of liquids) which can also be serious. Put simply, it is NECESSARY to totally abolish added salt and all foods containing sodium; citing a few: preserved in salt, in brine, aged cheeses, sausages, salted, bivalve molluscs, common bread, some baked goods such as crackers and breadsticks, broth cube with glutamate etc.
3. Chronic renal failure (CRI): it is the destruction of a large number of nephrons (functional unit of the kidney) following the work of a morbid process; chronic renal failure is often the consequence of the protraction of some diseases or nephrological disorders. The diet for chronic renal insufficiency is HYPOPROTEIC and if established early it allows a reduction in pathological progress, as well as a significant increase in life expectancy. The metabolic alterations present in chronic renal failure are different:

1. reduction of the expulsion of protein catabolites: urea, uric acid, creatinine, guanidine
2. impaired glucose tolerance and consequent hyperinsulinemia, hyperglucagonemia and increased gluconeogenesis
3. increase of VLDL lipoproteins and reduction of HDL
4. reduction of the excretion of sodium, potassium, magnesium, phosphorus and water
5. reduction of calcium absorption in the intestine due to the hypo-production of vitamin D3 (1-25 OH)
6. multi-vitamin deficiency
7. urinary loss of protein resulting in anemia.

The diet for chronic renal insufficiency should promote weight loss only at an early stage, as it could affect the pH of the blood later on, favoring metabolic acidosis. The "lipid intake" must be moderate and mainly made up of polyunsaturated fatty acids; with regard to proteins, it is better to guarantee a moderate intake of good biological value, and only in the case of urinary protein losses to reach 1.4g / kg of body weight. It is advisable to significantly limit the intake of some trace elements such as sodium, potassium and phosphorus, and at the same time supplement the diet with calcium, iron, folic acid and pyridoxine through the use of food supplements. In case of dialysis, it is advisable to keep in mind considering that this procedure favors the elimination of many water-soluble compounds (such as vitamins), therefore, it would be advisable to periodically provide for the fulfillment of specific needs.

Finally, remember that the diet for renal insufficiency is closely linked to the specific condition and the level of insufficiency; therefore, given and considering that the needs of the patient are constantly modified by the pathological progress, the diet administered must also be modified accordingly. Nevertheless, table salt MUST be totally eliminated regardless of the severity of the insufficiency and with it all the foods that contain it (see above, point 2); on the contrary, the protein intake must be evaluated exclusively on the basis of urinary losses of plasma proteins. In fact, although the catabolic products of amino acids can damage an already compromised system, the significant protein deficiency would have a greater (and decisive) effect on the state health of the patient with the manifestation of: edema, anemia, hypoalbuminemia, tissue deficiency, etc.

It may be necessary to use low-protein pharmaceutical foods (to limit the worsening of the nitrogen balance) and to evaluate the integration with modest quantities of essential amino acids. It is also advisable to drastically limit (and in some cases abolish) the use of foods containing high levels of quantity of potassium (legumes, mushrooms, dried fruit, bananas, preserved fruit juices) and phosphorus (milk, cheese, sausages, preserved meat and fish).
This kind of diet is to be considered a real clinical nutrition therapy, therefore, the weights MUST be respected with extreme precision even in the long term, in order to limit excesses and ensure a sufficient energy intake for the best maintenance of the state of health. .

Bibliography:

• Handbook of food science and dietetics - A. Raimondi, C. Lucas - page 191: 195