What should you eat to preserve your kidneys?

Monitoring the function of the kidneys is part of the routine medical checkup to ensure good general health. Since the kidneys have different roles and their functional decline may impact other organs in the body, it is important to identify a decline in status early. Nutrition has a huge impact both on the prevention and treatment of chronic kidney disease. Keep reading to learn more about the crucial role of your kidneys, the chronic kidney disease categories, what a healthy kidney diet looks like and more. 

What are the kidneys and why are they important?  

The kidneys are two organs located on each side of the backbone. They have a bean shape and are approximately the size of your fist.  

The kidneys are important for: 

• The elimination of drugs, poisons and metabolic wastes mainly related to the degradation of protein
• The regulation of the body’s fluid by retaining water into the body or excreting more water into the urine
• The regulation of the metabolic pH and electrolytes
• The regulation of the blood pressure
• The production erythropoietin, a hormone responsible for the stimulation of the bone marrow to produce red blood cells
• The activation of vitamin D

Inside the kidneys, there are nephrons which are responsible for the above roles. Each of the kidney contains approximately 1 million nephrons. As the function declines, the number of nephrons declines, which makes it harder for the kidneys to achieve their roles. In order to estimate the function of the kidneys, creatinine, a protein found in the blood, is being monitored. Based on the creatinine level, the Glomerular Filtration Rate (GFR) is estimated. Below are the chronic kidney disease categories based on the GFR levels: 

• Stage 1 (GFR >90): Minimal kidney damage, no intervention is required 
• Stage 2 (GFR 60-89): Mild kidney damage, nutrition intervention focuses on the prevention of further decline in kidney function 
• Stage 3 (GFR 30-59): Moderate kidney damage, nutrition intervention focuses on the prevention of further decline in kidney function AND the treatment of the comorbidities 
• Stage 4 (15-29): Severe kidney damage, nutrition intervention focuses on the treatment of the comorbidities AND transplant or dialysis is being considered 
• Stage 5 (<15): End-stage renal disease, transplant or dialysis is often initiated or moving towards end of life 

What diet should you follow when you have a low kidney function? 

Let’s be honest, there is lots of information on the web and unfortunately some of the recommendations out there may be more harmful than beneficial. Frankly, the answer to this question is “It depends”. There is no kidney disease diet that is right for everyone with kidney disease. However, there are some guidelines that can help prevent a decline in kidney function.  

Manage your blood sugar

If you have diabetes, make sure your blood sugar stays within the normal range. Hyperglycemia, high blood sugar, is the #1 cause of decline in kidney function.  

Lower your sodium intake

The second cause of chronic kidney disease is hypertension. A high blood pressure can damage or weaken the blood vessels in the kidneys resulting in a decline in function. Did you know that roughly 80% of the excess in sodium we eat is from the food we bring from the grocery and not the salt added while cooking? That means that the most control we have is while making choices at the grocery store; choosing lower or no added salt products and choosing fresh produce and proteins can have a huge impact on your health.  

Increase your fibre

Fibre is important for good digestion but also to lower the blood cholesterol which ultimately has an impact on the heart health and blood pressure. As described earlier, a high blood pressure is one of the main causes of chronic kidney diseases.  

The Mediterranean diet has been shown to have a positive impact on the prevention of the decline in kidney function as shown in this handout recently released by BC Renal, the British Columbia Kidney Agency. This style of eating emphasizes fresh foods, more specifically the daily intake of whole grains, fruits, vegetables and unsaturated fats such as olive oil, regular intake of plant-based protein and fish/seafood and more limited intake of red meats, poultry and dairy.  

To go back to the “It depends” from earlier, here are the tricky things with chronic kidney disease and diets. We are all unique on how our body reacts. Therefore, nutrients such as protein, potassium and phosphorus may not need to be adjusted at all, may need to be limited or may need to be increased… and this depends on your stage of chronic kidney disease, your comorbidities and even your medication or supplements. A registered dietitian can help individualize the diet that YOU need, one that takes into consideration your level of kidney disease, your lifestyle, and any other health conditions (like heart disease or diabetes) that may also need to be considered. 

If you or a loved one have a decline in kidney function, don’t hesitate to contact us for support in maintaining a healthy kidney diet. You will do yourself or your loved one a favor and prevent your health to worsen.  

 This article is based on The Essential Guide for Renal Dietitians, 4th edition, 2020, Canadian Association of Nephrology Dietitians (CAND) 

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