The work of the kidneys

The kidneys have several jobs; however, the main one is to clean the blood. The food we eat is digested by the stomach and nutrients are absorbed primarily in the small intestine. Water, glucose, small proteins called amino acids along with micronutrients such as calcium, sodium, potassium and phosphate (grouped together as salts) are all filtered by the kidneys. In well-working kidneys the balance between fluid and these molecules is tightly regulated so any waste is filtered from the blood and excreted out in the urine. Just as important, is the vital role of the kidneys in regulating blood pressure via a hormone system that manages blood volume.

What is chronic kidney disease (CKD)?

Aboriginal and Torres Strait Islander people are twice as likely to have signs of CKD compared with other Australians. One of the most common causes of CKD in Australia is diabetic nephropathy which is damage to the nephrons (site of filtration) caused by constantly high blood glucose levels in people living with diabetes. Click here to access the patient resource ‘How do my kidneys work?’.

Symptoms are often absent for a person with CKD, with up to 90% of kidney function being lost before symptoms are present. However, if detected early, CKD is treatable when managed appropriately.

Kidney function is measured by estimated glomerular filtration rate (eGFR) and early detection tests measuring microalbuminuria (ACR), blood pressure, and eGFR checks are recommended annually.

Preventing kidney disease

It is never too late to prevent kidney disease. Smoking, high blood pressure and high glucose levels all damage the kidneys. Some people think if they already have kidney damage it is too late to take care of them. It is never too late. If a person has early kidney damage it can be slowed down by up to 50%. This can mean it can take twice as long to need dialysis or a transplant for some people. 

Blood glucose levels

Eight out of ten Aboriginal and Torres Strait Islander people get kidney damage from diabetes. The higher the blood glucose levels are, the more damage can be done to the kidneys, so monitoring blood glucose levels and aiming to keep them in the target range is important. 

Blood pressure

Encourage people to have their blood pressure checked regularly and to take their blood pressure medication if needed, is important for good kidney health. 

Smoking

People who smoke are three times more likely to have kidney damage, and have a four to five times greater risk of a heart attack and stroke. 

Kidney health can also rely on maintaining good nutritional health and regular physical activity, which may also affect body weight. 

Nutrition and chronic kidney disease

There are five stages of kidney function in CKD and nutrition advice varies depending upon the progression through the stages. For people living with diabetes, the risk of CKD developing is reduced by managing blood glucose levels well, and in those with existing CKD, good diabetes management significantly reduces the progression. Generally, eating from the five food groups in adequate amounts to maintain good nutritional health, will assist in optimising blood glucose management and provide enough nutrients for an individual’s health assuming it is in line with the Australian Dietary Guidelines for Adults. 

Restriction of fluids and micronutrients such as potassium and phosphate is not necessary in the early stages of CKD; eGFR greater or equal to (≥) 30 ml/min/1.73m².  However, in the later stages of kidney disease, individualised dietary intervention involving an Accredited Practising Dietitian or renal dietitian is recommended. The renal dietitian can provide individualised advice based on the persons stage of CKD, health, lifestyle and preferences. It is important to recognise that the recommendations from the renal dietitian will change based on the person’s kidney function, medications, and blood and urine test results. 

So, what is a healthy way of eating when it comes to early stage kidney disease?

A healthy eating pattern may help to slow the progression of kidney disease, if accessible.

Recommend to people with early stage kidney disease to:

• Reduce or stop adding salt at the table and in cooking
• Limit packaged and very processed food products, and eat more vegetables, fruit, wholegrains and unsalted nuts
• Drink water and limit or avoid sugary drinks (e.g. soft drinks, cordial)
• Encourage people to choose foods from each of the five food groups for meals and snacks, for example:
  • Wholegrains e.g. whole oats, grainy breads, pasta
  • Vegetables
  • Fruit
  • Lean meat (steak or chops), fish, chicken, eggs, legumes, nuts and tofu
  • Low fat dairy milk, yoghurt, cheese or calcium-fortified soy products
  • Include some healthy fats like olive oil, avocado and canola oil and or margarine
  • Go easy on high salt, high fat, and high sugar containing foods such as fried foods, pastries, soft drinks etc.

A collaborative approach is always recommended in the management of CKD and discussing your client’s health with the general practitioner (GP) regularly may be necessary. In order to provide optimal care for the person, a GP may refer to a renal specialist doctor (nephrologist) and a renal dietitian.

For more healthy lifestyle and other helpful information on diabetes and CKD people can access the Diabetes Australia website here OR call the NDSS Helpline on 1800 637 700 to speak with a health professional.