Article written by :
Sudeshna Maitra Nag
MSc. in Food & Nutrition (C.U.)
Certificate in Applied Human Nutrition ( Cambridge University)
PGDM in Public Relation, Certified Diabetic Educator
Kidney is one of the major organs of our system. The main functions of kidney is to remove the toxic and waste products of our body through urine and to maintain the fluid and electrolyte balance. In kidney damage the toxins, excess protein and other electrolytes (potassium, phosphorus) get deposited in our body. This may lead to various ailments and death may also occur in the severe stage of kidney disease.
Different stages of Kidney/ Renal disease
Acute kidney disease (AKD)- Rapid deterioration of kidney function caused by injury or illness, which is often reversible.
Chronic kidney disease (CKD) – Abnormality of the structure or function of both kidneys lasting> 3 months, which is often progressive.
End stage renal disease (ESRD)- Chronic kidney disease that has progressed so far that the patients kidneys no longer function sufficiently to maintain life.
Malnutrition of multifactorial origin often develops in patients with advanced renal insufficiency. Dietary management takes very important role in management of kidney disease. Once symptomatic renal insufficiency has developed the patient should be guided by a Nephrologists and a Dietitian. Such patients are obviously at risk of azotemia (the accumulation of nitrogenous waste) as well as specific micronutrient abnormalities, including phosphorus/ potassium retention, impaired absorption of calcium/ iron and deficiencies of vitamin B6, folate, vitamin C and active vitamin D.
Adequate intake of water is important in the preservation of renal function over time. An intake of water equal to urine output plus 500ml is an appropriate guideline.
Studies indicate that protein restriction slows the progression of renal failure. It reduces glomerular flow and pressure and the accumulation of urea and creatinine. The benefit of protein restriction have been convincingly demonstrated for patients with a GFR (Glomerular filtration rate) below 70ml/1.73 m²/min.
Atherosclerosis affects renal arteries and is associated with renal insufficiency. Dietary intervention may be valuable in preventing renovascular disease. A high intake of fat and cholesterol may contribute to high glomerular pressure. There is evidence that while total saturated (butter, ghee) fat intake should be restricted, intake of polyunsaturated fat( cooking oil) should be liberalized.
Phosphorus restriction retards the progression of renal insufficiency. Low phosphorus diet tends to low in protein and vice versa. The deposition of calcium in renal tissue is reduced by low phosphorus intake. Serum creatinine rises as the content of calcium in renal tissue rises.
Tubular secretion of potassium tends to rise as GFR falls. When urine output falls below 1000ml per day potassium accumulation becomes a threat. In such patients potassium restrictions is required.
The restriction of protein and phosphorus often requires avoidance of dairy product. Calcium absorption is also impaired due to low level of active vitamin D. So patient of kidney disease are at risk of osteopathy. Supplementation of calcium is needed along with vitamin D. But in case of renal calculi restriction of calcium intake is needed.
Patients with a tendency to produce calcium oxalate stones may benefit from restriction of dietary oxalate. Food sources are chocolate, peanuts, spinach, fruits of berry group, soy products.
The metabolic conversion of ascorbate to oxalate suggests that high level of vitamin C intake increases the risk of stone formation. Urinary oxalate increases with high ascorbate intake. Thus vitamin C containing food should be restricted.
Magnesium tends to accumulate in renal failure. The restriction of protein and phosphorus generally serves to restrict magnesium as well.
Sodium filtration and reabsorption are reduced in kidney disease. In the severe stage sodium restriction is needed. Dietary sodium is related to urinary sodium levels and calcium excretion in urine. High salt intake is associated with calciuria and an increased risk of calcium oxalate stone formation.
Iron deficiency is relatively common in chronic kidney disease. But dietary sources of iron are restricted as most of the iron rich foods are rich in phosphorus, potassium, oxalate or magnesium. So supplementation is appropriate.
Kidney patients tend to have zinc deficiency. So supplementation will be appropriate.
Dietary restrictions place patients at high risk for deficiencies of vitamin B complex and folate. Supplementation is needed in case of dietary restrictions.
High fiber foods often contain protein of low biological value, potassium and phosphorus which may be poorly tolerated by patients in advanced stage.
OTHER ASPECTS OF KIDNEY DISEASE
Nephrotic syndrome: A condition with increased albumin catabolism and albumin losses in urine. In general restrictions of protein intake is recommended. But the protein intake must be of high biological value.
When kidneys are damaged and are no longer able to remove wastes from bloodstream, dialysis is needed. It is a treatment that filters and purifies the blood using a machine and maintains the fluids and electrolyte balance. Patients on dialysis tend to loss protein and would benefit from protein intake in the range of 1.0 to 1.2 gm /kg/ day. In dialysis patients 50% of ingested protein should be of high biological value.
Patients with kidney disease must maintain a lean body mass, whether or not on dialysis. Approximately 35kcal/kg energy is recommended on a daily basis.