Kidney Disease – Busting Food Myths

Diet in Kidney Diseases

A 55-year-old female was brought to the nephrology outpatient clinic in a wheelchair. She was only 35 kg in weight, dehydrated and was only skin and bone. She couldn’t walk without support and looked tired.

She had advanced kidney failure due to long standing diabetes and hypertension. She was 70 kg a few months ago and went on a diet treatment towards reducing her creatinine which pushed her into this situation.

She was given no salt and fluid restricted diet because of her increase in creatinine, no protein diet due to kidney failure, no carbohydrates in view of her diabetes and low-fat diet in view of protecting heart.

Then the question was, WHAT WAS SHE EATING?

There are gross misconceptions about the type of food to be taken in patients and their families with kidney diseases. Let us clarify the common doubts.

Salt and Fluid Allowance in Kidney Diseases:

Kidneys do multiple functions. Removal of extra salt and water, excretion of metabolic wastes like urea and creatinine, maintenance of the electrolyte and acid base balance, production of erythropoietin and active vitamin D hormone and control of blood pressure are some of its main functions. It is not necessary that if one of its functions is not done properly, the other function should be compromised.

This means that if the clearance of urea and creatinine is not proper, then excretion of salt and water could happen normally. There are two broad types of kidney diseases. One is called the ‘glomerular disease’ where the patient filters less amount of salt and water. Patients accumulate extra water as edema (swelling) and these patients need restriction of salt and water. Restriction depends on the severity of the swelling – the more the swelling, the greater the restriction.

The second group of patients have disease in the ‘reabsorbing units’ of the kidneys – Tubulo interstitial diseases. These group of patients pass more urine and have no swelling and there need not be any restriction of salt and water to these group of patients.

Therefore, the salt and fluid allowance depend on the urine output and the swelling status of the patients.

Protein Restriction in Kidney Diseases:

Proteins are needed for the functions of every cell in the body. The daily requirement is 1 mg/kg/day and an average Indian patient doesn’t eat this amount of protein daily. Though every text book talks of protein restriction in patients with kidney diseases, we should remember that these books are written by the Westeners for their patients who consume larger amounts of non-vegetarian proteins.

Indians are predominantly vegetarians and even the non-vegetarians don’t eat too much of animal protein. So, the restriction of proteins is limited to those who consume large amounts of animal proteins. A vegetarian and those who are malnourished need no protein restriction.

Also, creatinine is a waste product generated from muscles. So, if a patient is going to be placed on zero protein diet and loses the muscle mass, then the production of creatinine is less. This does not mean the kidney functions are improving.

Potassium Restriction in Kidney Diseases:

Potassium is an important electrolyte that is present in greater amounts inside each cell and very low levels are present in the blood. Any diet that is rich in potassium could increase the blood potassium to alarming levels that could cause dangerous effects including cardiac arrest.

The more severe the kidney failure, the risk of high blood potassium increases. Potassium restriction includes a hold on fruit juices, tender coconut water, vegetable soups, dried fruits and nuts and fruits. Vegetables, especially when eaten in large quantities like greens, could be leached and the water could be thrown out and then used.

Few fruits contain low potassium and these include apple, guava, pineapple, papaya and consuming them in small quantities is allowed.

Calcium and Phosphorus in Diet:

Kidney failure patients generally have low calcium and high phosphorus levels. It is important to understand that low calcium weakens the bones and high phosphorus causes risk to heart functions.

Milk, soybeans, cooked spinach, broccoli, okra, etc. contain good amount of calcium that could be allowed in moderation for patients to improve calcium levels.

Foods that contain high phosphorus like dairy products, custard, peanut butter, beans, whole grain products, bran cereals, cocoa and chocolate drinks need to be restricted.

Our patient was asked to take normal salt and water, good amount of proteins, carbohydrates and fats and she improved her nutritional status and was back on her feet. Our aim in prescribing diet to patients with kidney diseases needs better understanding and our aim is to maintain a healthy patient than pushing him/her into malnutrition.