Why diet matters in kidney disease
Healthy kidneys filter waste, remove extra fluid and keep levels of sodium, potassium, phosphorus and other minerals in balance. As kidney function falls, these can build up. High sodium raises blood pressure and causes fluid retention; high potassium can affect the heart rhythm; high phosphorus weakens bones and damages blood vessels. Diet also influences how quickly CKD progresses, through blood pressure, blood sugar and weight. Many people with early CKD need only general healthy eating with less salt, while those with advanced CKD or on dialysis need more specific changes.
Sodium (salt)
- Most guidelines suggest less than about 2,300 mg of sodium a day (about 5–6 g of salt) for people with CKD.
- Most salt comes from processed foods: bread, cured meats, cheese, ready meals, soups and sauces.
- Cook from scratch and flavour with herbs, spices, lemon and garlic instead of salt.
- Avoid salt substitutes containing potassium chloride unless your team approves them.
- Our guide to low sodium meals and snacks has ideas.
Potassium
Many people with CKD have normal potassium and do not need to restrict it; indeed, fruit and vegetables have benefits for blood pressure. If your blood potassium is high, your team may suggest limiting high-potassium foods such as bananas, oranges, potatoes, tomatoes, dried fruit and some juices, and using cooking methods such as boiling vegetables and discarding the water. See our guides to high potassium foods to avoid and low potassium foods.
Phosphorus
Phosphorus is found in protein foods, dairy, whole grains and, in highly absorbable form, phosphate additives in processed meats, cola drinks and some baked goods. When phosphorus is high, limiting additives is usually the most effective change, as they are almost completely absorbed. Your team may prescribe phosphate binders, taken with meals. Our guide to foods high in phosphorus explains label reading.
Protein
Protein needs change with the stage of kidney disease. For adults with moderate to advanced CKD who are not on dialysis and are metabolically stable, the KDOQI 2020 guideline suggests a low-protein diet (about 0.55 to 0.6 g per kg per day) or a very low-protein diet with supplements, under close dietitian supervision, to slow progression. People with diabetes may have slightly different targets. On dialysis, protein needs increase to about 1.0 to 1.2 g per kg per day because protein is lost during treatment. Plant proteins may be beneficial.
Kidney-friendly foods
- Fresh vegetables such as cabbage, cauliflower, peppers, green beans and onions.
- Fruits such as apples, berries, grapes and pineapple (lower in potassium).
- White rice, pasta and bread if phosphorus or potassium need limiting; whole grains otherwise.
- Egg whites, fresh fish and poultry in portions agreed with your team.
- Olive oil and other unsaturated fats.
- Herbs and spices for flavour.
- Water as the main drink, within any fluid limit set by your team.
Foods to limit with kidney disease
- Processed and cured meats.
- Salty snacks, ready meals and fast food.
- Dark cola and drinks with phosphate additives.
- Packaged foods with “phos” in the ingredient list.
- High-potassium foods if your potassium is high.
- Large portions of red meat.
- Herbal supplements and high-dose vitamins unless approved.
Fluids
People with early CKD usually do not need to restrict fluids. In advanced CKD and on dialysis, fluid limits may be needed to prevent swelling and breathlessness. Your team will advise on a daily amount. Thirst can be managed by reducing salt, sucking ice cubes or sugar-free sweets and using small cups.
Three common situations
- Stage 3 CKD with high blood pressure: reducing salt and following a Mediterranean-style pattern is often the main change.
- High potassium on blood tests: a renal dietitian can identify the main sources in your diet.
- Starting dialysis: protein needs increase and fluid and phosphorus usually need closer control.
Kidney disease with diabetes or high blood pressure
Diabetes and high blood pressure are the two most common causes of CKD. Good blood sugar control, a lower salt intake, weight management and regular physical activity help protect the kidneys. A dietitian can combine diabetes and kidney advice into one practical plan, as some recommendations, such as choosing whole grains or certain fruits, may need adjusting when potassium or phosphorus are high. Medicines that protect the kidneys are also important and should be discussed with your doctor.
Key points to remember
- There is no single renal diet; advice depends on stage and blood tests.
- Reducing salt helps almost everyone with CKD.
- Limit phosphate additives and adjust potassium only if needed.
- Protein needs differ before and during dialysis.
Questions about the renal diet
These answers are general information and do not replace an examination or individual medical advice.
What foods are good for your kidneys?
Fresh vegetables and fruit, whole grains (unless restricted), legumes, fish, olive oil and water, with less salt and processed food.
Are eggs good for kidney disease?
Eggs are a good protein source. Egg whites are lower in phosphorus. Your dietitian can advise on portions.
Can a renal diet reverse kidney disease?
Diet cannot reverse established damage but can help slow progression and prevent complications.
Is coffee bad for the kidneys?
Moderate coffee is generally fine for most people with CKD, but check with your team, especially if potassium is high.
Should I see a dietitian?
Yes. A renal dietitian provides personalised advice based on your stage, blood tests and treatment.
Sources
- Ikizler TA, et al. KDOQI clinical practice guideline for nutrition in CKD: 2020 update. Am J Kidney Dis. 2020
- NIDDK · Healthy eating for adults with chronic kidney disease
- NHS · Chronic kidney disease
This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.