Renal Diet Principles

Healthy kidneys excrete excess potassium, phosphate, sodium, water, and nitrogenous waste. As filtration declines, these substances may accumulate, but the degree of accumulation varies with kidney function, urine output, medications, dialysis, and the patient’s current laboratory results. That is why a renal diet is not one universal list of forbidden foods. It is a changing prescription based on trends. A patient with CKD may need potassium restriction during hyperkalaemia but not during a period of normal potassium or hypokalaemia. A patient may need fluid restriction with oedema and volume overload, yet require no routine restriction when volume status and urine output are adequate. The purpose is to reduce preventable complications without causing inadequate calories, protein-energy malnutrition, dehydration, or an unnecessarily narrow diet. Severe restriction can be harmful when it causes poor intake or weight loss. Dialysis also changes the plan. Dialysis can remove waste and electrolytes, but it does not make nutrition needs identical to those of a person with comparable CKD who is not receiving dialysis. Protein needs, fluid allowance, and electrolyte targets must be individualized.