Kidney and bladder health

15 June 2010

Your guide to renal nutrition

A healthy varied diet and keeping track of fluid and electrolyte intake is very important in chronic renal disease. Follow our list of important guidelines, provided by NICUS.

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The information explosion in the science of nutrition very often creates the impression that available information is contradictory. Consequently, it is no longer easy to distinguish between fact, misinformation and fiction. The Nutrition Information Centre of the University of Stellenbosch (NICUS) was established to act as a reliable and independent source of nutrition information.

A healthy varied diet is very important in chronic renal disease. The diet should provide adequate energy, and controlled amounts of protein, essential vitamins and minerals. An individualised diet plan is necessary to ensure that these goals are met.

It is also very important to keep track of fluid and electrolyte (mineral salts such as sodium chloride (NaCl) dissolved in water) intake. These important nutrients and recommendations will be covered in broad below.

General guidelines are provided for patients with chronic renal failure, excluding patients with end stage renal disease on haemodialysis and peritoneal dialysis. Follow-up publications will cover these nutrient recommendations in more detail.

The role of a healthy body weight in preventing chronic renal disease

It is now generally accepted that obesity (Body Mass Index [BMI] > 30), as well as overweight (BMI > 24.9), increases the risk of a number of chronic diseases including insulin resistance, hyperlipidaemia, hypertension and stroke, type 2 diabetes, and cardiovascular disease, as well as cancers of some sites.

Recent evidence revealed that obesity also plays an important role in the development or initiation of chronic renal disease amongst patients with otherwise normal kidney function. It is very important to attain and maintain a healthy body weight in the protection of renal function, especially for patients with Type 2 diabetes.

Furthermore, obesity can potentiate the progression of underlying renal disease to end stage renal failure.

Globally the following general nutrition guidelines are recommended to prevent obesity:

  • Achieve energy balance and a healthy weight
  • Limit energy intake from total fats and shift fat consumption away from saturated fats (meat and dairy) to unsaturated fats (nuts, olives)  and towards the elimination of trans-fatty acids (fried and baked goods).
  • Increase consumption of vegetables, fruit and legumes, whole grains and nuts
  • Limit the intake of free sugars
  • Limit salt (sodium) consumption from all sources and ensure that salt is iodised

Body Mass Index is an index to determine if your current body weight is healthy or unhealthy.
 

How to calculate your Body mass index (BMI) (kg/m2)

            BMI = weight (kg) ÷ height 2 (m)

 

BMI

Interpretation

< 16

Grade 1, chronic energy deficient

16 – 16.9

Grade 2, chronic energy deficient, moderate underweight

17-18.5

Grade 1, chronic energy deficient, mild underweight

18.5 – 24.9

Healthy

25 – 29.9

Overweight (pre-obesity)

30 – 34.9

Obesity, class 1

35 - 39.9

Obesity, class 2

≥ 40

Morbid obesity, class 3


Alternatively waist circumference (cm) – can also be used to determine the risk of metabolic complications:

Increased risk: Men: ≥94cm; Women: ≥80cm
Greatly increased risk: Men ≥102cm; Women: ≥88cm 

It is also very important to prevent under nutrition and underweight as the disease progress to end stage renal disease, since rapid weight (more than 10% of body weight in 6 months) loss and malnutrition also put a patient at risk.

General nutrition recommendations for patients with chronic renal failure

Protein

Protein is important to the body. It helps the body repair muscles and fight disease. Unhealthy kidneys lose the ability to remove protein waste from the blood which then starts to build up in the blood. As kidney function continues to decline, more waste accumulates. Blood tests that measure protein waste include blood urea nitrogen (BUN) and creatinine.

At first, only small amounts of albumin (a protein) may leak into the urine of some patients, a condition known as microalbuminuria and a sign of deteriorating kidney function. As kidney function worsens, the amount of albumin and other proteins in the urine may increase, and this condition is called proteinuria. A lower protein diet may be prescribed to help reduce waste accumulation and to protect the kidneys from more damage.

Dietary protein comes mostly from meat but can also be found in eggs, milk, nuts, legumes, and in smaller amounts from other foods such as grains. Dietary protein intake for chronic renal failure is based on the stage of kidney disease, nutritional status and body size.

Patients with chronic renal failure/disease should avoid eating too much protein which will increase the protein load on the kidneys. Ideally patients should work with a dietitian to prescribe the correct diet plan. Furthermore high protein foods such as meat, milk and eggs can be high in saturated fat and cholesterol which should be limited, especially for patients with high cholesterol or cardiovascular disease and diabetes.  Good choices include fish, chicken breast, lean red meats, low fat soy products as well as low fat dairy products.

Patients with chronic renal failure may be allowed more total fat than the general population (up to 35% of the total energy), but the type of fat is important. Healthy fats such monounsaturated and polyunsaturated fats found in vegetable oils, soft (tub) margarines, olives, avocados, nuts, and seafood are recommended.

Salt/Sodium Chloride

Modern diets contain too much salt, and patients with chronic renal failure should lower sodium intake to prevent high blood pressure and fluid retention and overload. In patients with chronic renal failure sodium intake should be limited to 1000 – 4000 mg/day depending on their blood pressure and fluid status.

The main source is table salt, or sodium chloride (NaCl). One teaspoon (5 g) of salt contains approximately 2 000 mg of sodium. This allows only small amounts of salt to be used in cooking, but means limiting very salty foods, and not adding salt to food after it has been cooked.

Salt substitutes such as 'Lo-Salt' are not suitable for patients with renal failure, because they contain large amounts of potassium.

Potassium

Potassium is essential for nerve and muscle (including heart) function and for electrolyte balance.   Patients with advanced renal failure cannot excrete an excess of potassium in the urine so that blood levels of potassium rise. This can be dangerous to the heart and may even cause death.  

In patients with advanced chronic renal failure potassium intake should be limited to 2000 – 3000 mg/day or 40mg/kg/day depending on the blood levels of potassium. Potassium is found particularly in leafy vegetables and most fruit and fruit juice, and in potatoes, especially if they are fried or baked. A dietitian will provide a patient with chronic renal failure with lists of low and high potassium foods (starches, vegetables and fruit).

Phosphate

Phosphorus is a mineral that builds up in the blood as kidney failure progresses. Too much phosphate in the blood (hyperphosphataemia) usually becomes a significant problem in the later stages of renal failure (stages 4 and 5, usually less than 20% kidney function). It may damage the kidneys, other organs, and cause the skin to itch.

In patients with chronic renal failure phosphate intake should be limited to 800 – 1000 mg/day. Phosphate is found in association with protein, especially in milk and cheese. Dairy products, dried beans and peas, nuts and seeds, peanut butter, wholegrain cereals, baking powder, shellfish and some soy products are high in both protein and phosphorus.

For further, personalised and more detailed information, please contact NICUS (e-mail: nicus@sun.ac.za or phone 021-933 1408) or contact a dietician registered with the Health Professions Council of South Africa 

(Acknowledgement: RenalSmart Nutritional Information SystemReferences from the scientific literature used to compile this document are available on request.)

- (NICUS, Health24, June 2010)

Read more:

Renal nutrition: phosphate recommedations
Renal nutrition: potassium and sodium
Renal nutrition: fluid intake

 

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