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Diet in CKD ( Chronic Kidney Disease)

Changing patterns of diet in patients with kidney disease

Traditionally diet plays an important role in any disease. The first doubt the patient has is what to eat when he has any medical problem. To understand the concept of diet in patients with kidney disease, we should know briefly the functions of the kidneys.

  • Basically the kidneys excrete products of metabolism. The food we eat is broken down into simpler components obsorbed to produce energy in the body.The main component of the food for example protein is broken down into amino acids which then release ammonia as an end product. Ammonia is converted to Urea in the liver and Urea is removed by the kidneys. Similarly, proteins, especially animal proteins, produce acids which are excreted by the kidneys. Hence when kidneys are diseased the blood urea levels go up and acid accumulation takes place in the body.

  • The second function of the kidney is to maintain the internal environment of the body (i.e) the acid-base electrolytes and water balance. It is the responsibility of the kidneys to correctly remove the exact quantity of water so that we are neither dehydrated nor bloated. Similarly we add a lot of salt in our diet (sodium chloride) to improve the taste of food and it becomes the duty of the kidneys to remove this extra salt so that we do not develop high blood pressure. Various minerals including potassium are found in natural foods which again are excreted by the kidneys.

Protein intake

Historically the first diet that was recommended for patients with kidney failure was the rice-potato diet which was based on the concept that proteins should be avoided to the maximum and the patients should get energy from carbohydrates. This would then result in decreased production of urea

Similarly, barley was promoted as an important food group since it is purely a carbohydrate. Subsequently patients were allowed the 20gm protein including vegetable and animal proteins. The biggest drawback of the above diets was that the Urea levels came down but patients became under nourished and the quality of life suffered. Hence the present concept where the protein restrictions mainly holds for the western diet to 40-50 gms per day. The vegetarian diet does not contain enough protein for restrictions. So the average Indian vegetarian diet is more or less tailor made with regards to the protein intake in patients with kidney failure. It is also important to differentiate whether patients suffer from acute or chronic kidney failure. In acute kidney failure where there is temporary cessation of kidney function , nutrition is very important for the recovery of the patient. Hence protein restriction is not advocated. Whereas, in chronic renal failure where the kidneys are irreversibly damaged, protein reduction to 40gms per day, especially animal protein, is advocated early in the disease to prevent progression. When the disease is advanced , protein restriction is not recommended since patients will become undernourished.It has been scientifically shown that vegetarian diet reduces the progression of CKD.

Salt intake

Salt refers to sodium chloride and not Urea as confused by lay people. Not all patients with kidney disease require salt restriction. Only those who have swollen legs require salt restriction. Salt substitutes are dangerous since they contain potassium.

Water intake

There is a misconception that large quantities of water will improve kidney function in all patients. On the contrary, in some patients with kidney failure, water accumulates in the body resulting in low sodium levels (hyponatremia). Hence water or fluid restriction (which will vary from patient to patient) is important.

Potassium intake

Almost all patients with kidney failure require potassium restriction in the diet. High potassium is found in fruit juices, coconut water, dried fruits, red meat and others.

Stone disease

Patients with kidney stones once again require a change in diet. Originally since majority of the stones are calcium oxalate stones, low calcium and oxalate diet were recommended. However it has been shown that restriction of calcium on the contrary leads to loss of calcium in bones and continuation of stone formation. Hence low calcium diet is not advised. Similarly tomatoes have become notoriously responsible for stone formation - which is not correct. It has been found that high protein in the diet leads accumulation of uric acid and highly acidic urine. This inturn precipitates stone formation. Also high salt in the diet drags the calcium along with sodium in the urine resulting in stone formation. Hence the present recommendation is a low protein and low salt diet for patients with kidney stones. An acidic urine results in burning especially when there is urinary tract infection. A diet with large quantities of vegetables makes the urine alkaline and relieves the symptoms.

Further reading

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