All You Ever Wanted To Know
Patients with Chronic Kidney disease(CKD) have many misconceptions as far as diet is concerned. Their dietary advice is loaded with don'ts more than the do's.
Dietary protein restriction is often over-emphasized as proteins are considered to be the major factor for aggravating further the failing kidney problem. We will address the common dietary advices to CKD patients and myths surrounding them.
Proteins are not synthesized in the body, hence they have to come from the food we eat. Our body tissues, muscles are made up of proteins. Amino acids are the building blocks of proteins. A certain amount of daily protein intake is needed for these tissues to stay healthy and function normally.
Tissues are normally broken down to certain extent every day, depending on our activity or underlying disease which can cause their excessive breakdown as in fevers, septic conditions or trauma. If protein intake does not match this amount of turn-over, malnutrition will result.
Kidneys excrete the break-down products of the food we consume including products of protein catabolism. This includes urea, creatinine, uric acid, chemicals in their simple form and some heavy metals. Higher the dietary intake of protein, more is the work needed to be done by the kidneys.
Some amino acids help increase the blood flow across the glomerulus increasing the pressures there. Higher the pressure in the glomerulus, more would be the wear and tear of the glomerulus. This is exaggerated in a diseased glomerulus, i.e. patients having chronic kidney disease.
Moreover, when there is protein leaking in the urine, this protein traverses through the tubules of the nephron and can cause damage to these tubules, further aggravating the disease.
Therefore, if someone has been diagnosed with CKD, his protein intake is assessed and if he is taking proteins more than 1 g/kg body weight per day, protein restriction is advised.
Guidelines are provided by International organizations (KDOQI, American Dietetic Association) about the calculation of protein intake by such patients. So, calculated protein restriction is advisable rather than a complete absence of proteins in the diet. A nutritionist can definitely guide in this regard to help delay the progression of kidney disease.
Proteins can be classified as
High Biological Value(HBV) or First Class Proteins(FCP)
Biological Value is an index of protein quality that reflects the percentage of absorbed nitrogen from dietary protein actually retained by the body.
The greater the proportion of Nitrogen retained, the higher is the Biological Value (BV) or quality of the protein being tested.
HBV proteins are present in
Milk & milk products.
Meat and poultry.
Fish and seafoods.
Proteins with a low Biological Value or second class proteins. They are
Proteins in dals, legumes and pulses.
Proteins in nuts and oilseeds.
Proteins in cereal grains.
Proteins in vegetables.
Soy protein is considered the best in vegetarian proteins, but it has some limiting amino acids(those which are in less amounts). It has a BV of 75, while eggs have a BV of 87-97.
Dietary protein intake in chronic kidney disease (CKD) depends on the Glomerular filtration Rate (GFR)
In CKD, the protein intake should be 0.6-0.8 g/kg body weight/day.
For example: A 60 kg man with CKD should take 35-50 gm of proteins per day.
However, most Indian vegetarian diets contain less than 35 gm of proteins.
So, in a given individual with CKD, protein intake should be calculated from the diet history, and only if it crosses 50 g/day or 0.8 g/kg body weight/day, should it be restricted in diet.
Conversely, if it is less than 35 g/day or 0.6 g/kg body weight/day, it should be increased in the diet.