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Kidney health and nutrition

Functions of the kidney

The kidneys filter blood removing waste products (urea and creatinine) and excess fluid through urine, as well as keeping bodily salts (sodium, potassium and phosphate) and acid in balance. They also release hormones which affect bone structure (vitamin D), the creation of red blood cells (erythropoietin) and the regulation of blood pressure.

Main causes of kidney damage

Risk factors that could damage your kidney function include diabetes, high blood pressure, obesity, chronic overuse of certain medications, infection, and disorders such as polycystic kidney disease.

Measuring kidney function

It is important to know your kidney function. Kidney disease develops over a prolonged period and symptoms are often only noticed when the disease is very advanced. Your kidney function can be tested through a simple and non-expensive blood test, called the eGFR (estimated glomerular filtration rate).
A consistent eGFR of less than 60 ml/min over a period of three months indicates that you have chronic kidney disease (CKD). Your doctor will refer you to a specialist, but it is also important that you consult a dietitian. Ask your doctor for a referral to a dietitian if he/she has not referred you as the progression of CKD may be slowed down through a few easy dietary modifications.

Stages of CKD

CKD is divided into five stages related to eGFR.
Stage 1: eGFR 90 – 130 ml/min: Still normal kidney function.
Stage 2: eGFR 60 – 89: Mild decrease in kidney function.
Stage 3: eGFR 30 – 59: Kidney function is moderately decreased.
Stage 4: eGFR 15 – 29: Severe decrease in kidney function.
Stage 5: eGFR < 15: End-stage kidney disease and treatment is necessary, i.e. dialysis.

Dietary requirements

The waste products and fluids that the kidneys normally remove from the blood come from consumed foods and liquids. To treat and prevent further deterioration of kidney function, a special diet is needed to control the buildup of waste and fluid in the blood and to reduce the workload of the kidneys. This diet limits daily intake of protein, salt, phosphorus, and as necessary, potassium and fluid, according to your stage of CKD.

  • Protein
    Reducing dietary protein intake reduces the urea level (the uremic load on kidneys) and can help preserve kidney if your kidney function is compromised. It is recommended that the intake of red meat is reduced to no more than two portions per week and that it is more often substituted with poultry, fish and plant-based protein sources.
  • Salt (sodium)
    It is recommended that the intake of salt is restricted as it has a direct toxic effect on the kidneys and contributes to high blood pressure and fluid build-up in the body. Sodium is found not only in table salt but also in powdered soups, processed foods, pre-prepared meals, “fast foods”, pickled and tinned foods, as well as in smoked foods such as ham, bacon and processed meats. Rather substitute the use of salt/sodium chloride with herbs and spices.
  • Phosphorus
    When your renal function is impaired, the excretion of phosphate through the kidneys is also impaired. It is recommended to start restricting dietary phosphates when the eGFR drops below 60 ml/min. Even if you are on dialysis, phosphate levels will accumulate in the blood if dietary phosphate is not restricted. Eventually, these high phosphate levels will cause “soft bones” and “hard arteries”. Bones will become brittle as calcium will be taken from bones to bind to the excess phosphate in the blood. These calcium-phosphate crystals will also cause arteries to narrow and harden contributing to increased blood pressure and cardiovascular disease.

    Natural phosphate is found in many foods such as meat, legumes, nuts and dairy products. The phosphate from especially dairy products is very well absorbed and therefore, restricting dairy products from your diet, is essential to restrict your phosphate levels in your blood. A renal dietitian will be able to help you restrict your phosphate intake without unnecessarily omitting important food groups from your diet completely.

    Phosphate is also added as a preservative to packaged and processed food items that come in a box, bag or jar. The body absorbs 100% of this added phosphorus causing a processed diet a major contributor to high phosphate levels.


Below is the Phosphate content / 250ml:

  • Cow’s milk 220 – 230 mg
  • Soya milk 123 mg
  • Oat milk 120 mg
  • Rice milk 58 mg
  • Almond milk 20 mg

How to make your own...

You can make your own kidney-friendly oat milk and almond milk with a handful of ingredients.

Oat milk
• 1 cup rolled oats
• 4 cups water
• 1 whole date (pitted) or 1 tablespoon honey (optional)
• 1/2 teaspoon vanilla essence / extract (optional)

Place these ingredients in a blender at high speed for 1 minute. Use a very thin towel or cheesecloth to drain out oat milk and discard oat remnants. Store in a closed container in the refrigerator for 2 to 3 days.

oat milk recipe

Almond milk
• 1 cup almonds
• 4 cups water
• 1 whole date (pitted) or 1 tablespoon honey (optional)
• 1/2 teaspoon vanilla essence / extract (optional)

Place these ingredients in a blender at high speed for 1 minute. Use a very thin towel or cheesecloth to drain out almond milk and discard almond remnants. Store in a closed container in the refrigerator for 2 to 3 days.

Almond milk recipe
  • Potassium
    Potassium is a mineral and an electrolyte found in most foods especially fruit and vegetables. When your kidneys are damaged, potassium may accumulate in your blood. When potassium levels are very raised, an irregular heartbeat or heart attack like symptoms may occur.
    Potassium intake may require some restriction in the diet but needs to be individualised depending on the reason for the high potassium level. Non-diet related causes of a high potassium level could be high blood sugar levels in diabetics, rapid weight loss accompanied by muscle breakdown, acidosis and constipation. Ask your doctor to refer you to a renal dietitian if you are unable to control your potassium levels.
  • Fibre
    Benefits of adequate dietary fibre intake in CKD, and adding a fibre supplement if needed, include preventing constipation and elevated potassium levels, lowering urea levels (uremic load on kidneys), and lowering cholesterol levels. A high fibre intake in the form of plant foods such as wholegrains, fruit and vegetables, help to lower the acid load in the body and prevent metabolic acidosis, which has been found to prevent ongoing damage to the kidneys.

Tips for improved kidney health

  • Achieve and maintain a healthy body weight
  • Manage all health conditions optimally, such as hypertension and diabetes
  • Drink daily the adequate amount of fluid, preferably water
  • Reduce the intake of red meat to no more than two portions per week and substitute with poultry, fish and plant-based protein sources
  • Limit the intake of salt and salty foods
  • Increase the intake of fresh, whole foods and limit the intake of processed and ready-to-eat foods
  • Increase daily fibre intake
  • Depending on the stage of CKD, restrict protein, sodium, phosphate and potassium intake
  • Do not smoke
  • Use medication as prescribed by your doctor. Do not use over the counter medication without consulting your doctor first.

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