Diet for chronic kidney disease: what to eat at each stage

What role does diet play in chronic kidney disease?

Diet can help slow the progression of chronic kidney disease and delay dialysis. As the glomerular filtration rate falls—the volume of blood the kidneys filter each minute—waste products from protein build up. The body also finds it harder to regulate potassium, phosphorus and sodium.

There are two aims: protect the nephrons, the small filters in the kidneys that are still working, while eating enough to avoid losing muscle. Each stage and each set of blood test results calls for individual decisions agreed between your dietitian and nephrologist.

How does your diet change at each stage of kidney disease?

Stages are defined by the glomerular filtration rate, in ml/min/1.73 m² [1]. They range from G1, at 90 or above, to G5, below 15; G2 (60–89), G3a (45–59), G3b (30–44) and G4 (15–29) fall in between [1]. Broadly speaking, this is what changes on your plate.

• In stages 1 and 2, a healthy diet with little salt, few ultra-processed foods and no excess protein is usually enough.
• In stages 3 to 5 without dialysis, protein is adjusted and, depending on your blood test results, so are potassium and phosphorus.
• On dialysis, protein intake increases again because some is lost during treatment.

How much protein can you eat with kidney disease?

Digesting protein produces urea, a waste product that damaged kidneys have difficulty removing. Cutting protein too much, however, leads to muscle loss and weakens your defences.

International kidney disease guidance recommends adjusting protein according to the stage and risk of progression [1]. Your nephrologist or dietitian will tell you how much protein, potassium, phosphorus and other ions and minerals are right for you at your stage [1].

Another guideline, focused on nutrition, also suggests reducing protein further for people who are not on dialysis, always with close supervision [2]. Your specific plan depends on your filtration rate and nutritional status.

If you are already on dialysis

With haemodialysis or peritoneal dialysis, the opposite applies because some protein is lost during treatment. Your team will adjust your intake to make up for that loss [2]. If you are admitted to hospital while receiving haemodialysis, your plan will be reviewed again [3].

How to lower potassium without cutting out fruit and vegetables

Your muscles and heart need potassium. When the kidneys filter less, potassium can build up in the blood and disturb the heart rhythm; this is called hyperkalaemia. Cutting out all fruit and vegetables, however, makes your diet less balanced and can contribute to constipation.

That is why potassium is adjusted to your blood test results and the medicines you take [1] [2]. It is restricted only when your results call for it. If your nephrologist asks you to moderate it, change how you cook.

Cut vegetables and potatoes into thin pieces and soak them for several hours, changing the water. Then boil them in two changes of water. Bring them to the boil, discard the first water and finish cooking in fresh water. A good deal of the potassium stays in the water you discard.

Which phosphorus should you watch most closely with kidney disease?

High blood phosphorus weakens bones and encourages calcification of the arteries and heart valves. Legumes and nuts used to be heavily restricted. We now know that not all phosphorus is absorbed in the same way [2].

Almost all the phosphorus in additives is absorbed, between 90 and 100% [2]. Phosphorus in plant foods is bound to phytates and is absorbed much less, between 20 and 50% [2].

So the first step is to avoid ultra-processed foods with added phosphates. On labels, look for phosphoric acid, phosphates or additives E-338 to E-341, E-343 and E-450 to E-452. Your nephrologist will decide on any further restrictions based on your phosphorus and parathyroid hormone levels.

How much salt and fluid can you have?

When the kidneys fail, they retain sodium and water. This raises blood pressure and causes swelling in the ankles, legs and eyelids, a common form of fluid retention.

To help control blood pressure, international guidance suggests less than 2 g of sodium a day, or less than 5 g of salt [1]. That is just under a level teaspoon, including the salt already in food. Salt-wasting kidney conditions are an exception; your nephrologist will manage these. Remove the salt shaker from the table and cook without salt.

There is no fixed rule for fluids. In the early stages, if you have no swelling, drink according to thirst. If you are urinating much less or have heart problems, your nephrologist will set a limit. This limit includes water, stock and milk.

Common mistakes we see in consultations

Three mistakes come up repeatedly in consultations, and all three can be addressed.

Eating less and less out of fear. Faced with so many lists of foods to avoid, many people cut back until they do not get enough energy. When energy intake is too low, the body breaks down its own muscle and urea rises—the very thing you were trying to prevent [2]. As a general guide, energy needs are 25 to 35 kcal per kilogram of body weight per day, depending on your age and activity [2].

Malnutrition is also common in people admitted to hospital with kidney disease and worsens their outcomes [3]. Olive oil and planned portions of rice, pasta or potatoes help you get enough energy without adding minerals. If you have lost weight without trying, tell your team; we also support weight gain.

Following someone else’s list. Forums and groups share lists of foods you cannot eat with kidney disease. Many are meant for people on dialysis or with high potassium. If your potassium and phosphorus levels are fine, those restrictions only reduce variety and energy.

Looking for something to “cleanse” your kidneys. Many stocks and herbal teas claim to do this, but none can. The kidneys do not collect dirt that can be washed away. Some plants can also provide a lot of potassium, while others are toxic to the kidneys. Check any herbal remedy with your doctor [1]. Protecting your kidneys means controlling blood pressure and blood glucose, taking prescribed medicines and following your eating plan [1].