Diet in chronic kidney disease

It's important for everyone to have a healthy balanced diet, and this includes people with CKD. See the separate Healthy Eating leaflet for more information.

If your kidney function is becoming worse (stage 4 to 5), you will probably be referred to a specialist in renal (kidney) medicine. Some people with advanced kidney disease need to follow a special diet. If this is the case, you should be seen by a specialist dietician who can give you advice about what you should eat.

Salts (electrolytes)

Some of the chemicals or salts that healthy kidneys balance are sodium, potassium and phosphate. If they are not removed by the kidneys, their levels can build up in the body.

Sodium

Sodium in the diet primarily comes from eating salt. Too much sodium can cause high blood pressure, and high blood pressure can cause further damage to the kidneys. People who have CKD should aim to eat no more than 2-3 g of sodium daily. Avoid adding salt to your food when cooking or at the table. Also, try to avoid buying foods which are high in salt, such as:

• Bacon and other cured meats.

• Hard cheese.

• Yeast extract.

• Stock cubes.

• Salted nuts and crisps.

However, there is also quite a bit of salt in bread, breakfast cereals, biscuits and sauces. Checking the labelling on the packet will help you to look for brands which are lower in sodium.

Many 'low sodium' salt substitutes (like LoSalt® and So-Low®) contain potassium instead of sodium. If you've been advised to eat a low-potassium diet (see below), you should avoid these.

Potassium

Normal blood levels of potassium help keep your heart beating steadily. The kidneys are usually good at controlling the amount of potassium in the blood, and can still do this well in early CKD. However, when the kidneys are not working well (like in advanced CKD), potassium levels can become dangerously high. Dangerous heart rhythms may result, which can lead to death.

You only need to follow a low potassium diet if you've been advised to by your healthcare team. Most people with early-moderate CKD (stages 1 to 3) don't need to limit their potassium intake, unless told otherwise. Low potassium diets are generally only recommended in people who've had a blood test showing high potassium levels, which can occur with later-stage CKD (stages 4 to 5). This is particularly likely with stage 5 CKD.

If you have CKD and are not sure if you should be following a low-potassium diet, speak to your healthcare team.

Potassium is found in many food groups, including fruits and vegetables. Choosing items from the lower potassium groups can help to control your potassium levels.

When eating fruits

Choose peaches, grapes, pears, cherries, apples, berries, pineapple, plums, tangerines, watermelon, cranberries and strawberries.

Limit or avoid oranges and orange juice, nectarines, kiwis, raisins (or other dried fruit), bananas, cantaloupe melon, honeydew melon, prunes and nectarines.

When eating vegetables

Choose broccoli, cabbage, carrots, cauliflower, celery, cucumber, aubergine, green and wax beans, lettuce, onion, peppers, watercress, courgette, bean sprouts, sweetcorn and mushrooms.

Limit or avoid asparagus, avocado, potatoes, tomatoes or tomato sauce, butternut squash, pumpkin, artichoke, sweet potato, beetroot, Brussels sprouts and cooked spinach.

When eating other foods

Choose pitta, tortillas and white breads, white rice, beef and chicken.

Limit or avoid higher-fibre whole grains (such as brown rice or bran) and beans (for example, baked beans).

Avoid 'low sodium' salt substitutes like LoSalt® and So-Low®. These have high levels of potassium. Check the labels of processed and packaged foods as well, particularly if they're labelled as 'low sodium' - these often contain potassium salt substitutes.

Phosphate

Phosphate and calcium are important for bone strength. If the phosphate level becomes too high it will reduce the calcium level and that can weaken the bones. High phosphate can also cause itching. Healthy kidneys are good at controlling phosphorus levels by getting rid of any excess. In early-to-moderate CKD (stages 1 to 3) the kidneys are usually still able to do this, and so you probably don't need to worry about phosphate levels if you are at this stage. In CKD stage 4 and 5, blood phosphate levels can start to rise, and you might be advised to make dietary changes to reduce them. You might also be advised to take phosphate binder medicines.

Foods lower in phosphorus

• White bread, pasta and rice.

• Most fruits and vegetables.

• Corn or rice cereals, popcorn.

• Some light-colored sodas and lemonade.

Foods higher in phosphorus

• Processed meat (including poultry) and fish.

• Wholegrain bread.

• Dairy products.

• Bran cereals and oatmeal.

• Nuts and sunflower seeds.

• Dark-colored colas.

• Vegetables such as sweet potatoes, peas and mushrooms.

• Pulses such as lentils.

Protein

The kidneys remove waste products of protein from the body as a chemical called urea. In the past, diet advice for people with kidney disease has included advice about restricting protein. However, current advice looks at getting a good balance: not too much and not too little.

Foods which contain protein include meat, fish, eggs, cheese, pulses and nuts.

A diet which is too low in protein can lead to muscle wasting and fatigue. Such a diet can also lead to problems with insulin and blood sugar levels.

There is some evidence that plant-based diets are good for people with CKD, and might slow down the rate at which CKD gets worse. A plant-based diet is one that is mostly based on eating foods that come from plants, such as fluids and vegetables, pulses, whole grains, nuts, seeds and oils. Some plant-based diets still include meat and fish, but are mostly based around plant-based foods. Examples include the Mediterranean diet, the DASH diet, and the UK's Eatwell Guide. Other plant-based diets exclude meat and fish, such as vegetarian and vegan diets. It's a good idea to move to a more plant-based diet, if you feel you are able to. Read our feature on 5 easy vegan swaps to make within your diet.

Fluid intake

The kidneys balance the overall water level in the body (hydration). It's a good idea to maintain a good fluid intake, because dehydration can have bad effects on kidney function. The national recommendations in the UK are to drink about 6 to 8 glasses of water and other liquids a day - lower-fat milk and sugar free drinks like tea and coffee also count.

In early-to-moderate CKD (stages 1 to 3), the kidneys are usually still able to control water levels in the body. In more advanced CKD (stages 4 and 5), the kidneys can struggle to control fluid levels, and people may develop fluid retention, or fluid overload. If this is the case, you might be advised to reduce the amount of fluid you are drinking. Your renal doctor or your dietician will be able to advise you about this.

Alcohol

There are no special guidelines about alcohol intake for people with kidney disease. However, it is sensible to stick to the usual alcohol guidelines of no more than 14 units of alcohol per week, spread across several days.

Vitamins

Healthy kidneys make vitamin D, so even people with early CKD should be taking vitamin D supplements. Vitamin D is important for bone strength. You may need to take additional calcium with the vitamin D.

Other vitamin supplements may be helpful if you have had a poor diet for a while. CKD can cause a reduction in appetite and feelings of nausea.

Vitamin supplements containing vitamin A should be avoided. Multivitamins are not recommended unless you have had weight loss surgery or if you have malabsorption.

Iron

The kidneys have a role in making red blood cells, so CKD can lead to anaemia. Iron levels can also be low if your diet is not very good. Your doctor may prescribe you some iron tablets to take if your iron levels are low.

Maintaining a healthy weight

It is important to maintain a healthy weight if possible, to reduce the risk of other conditions developing.

CKD can cause a reduction in appetite as the condition progresses. A dietician can advise you which foods will help you to avoid losing weight. If you find it difficult to eat enough in regular meals, your doctor may recommend some food supplements to help you maintain your food intake.

Obesity can cause problems if your CKD has progressed far enough to require dialysis or a kidney transplant. If you are trying to lose weight, ask your doctor's advice. A steady weight loss with a low-fat plan including lots of fruits and vegetables will be a better option for your kidneys than a diet of low carbohydrates and high protein.

Herbal supplements and traditional medicines

Some people are interested in taking herbal remedies, supplements, and traditional medicines, such as traditional Chinese medicine. People with CKD should be cautious about taking these. Some herbal medicines can cause damage to the kidneys and make CKD worse. Herbal medicines and supplements can also affect how prescription medicines work, which can cause serious problems. There's also little evidence to suggest that they work.

It's generally best to avoid herbal remedies, supplements and traditional medicine remedies if you have CKD. If you do want to take them, speak with your healthcare team first.

Dialysis

If your kidney function worsens, your specialist may decide that you need to start dialysis. Haemodialysis is a procedure where your blood is passed through a machine to remove the waste products (as your kidneys would do if they were working). In peritoneal dialysis, fluid is pumped into your abdominal cavity to remove the waste products.

The advice about eating and drinking is slightly different for people who are on dialysis.

Phosphate

Phosphate is not removed very well by dialysis. Therefore, you may need to take medication called phosphate binders to reduce the level of phosphate in the blood.

Protein

If your kidney function is worsening so much that you will need to start dialysis soon, your doctor will probably ask you to reduce your protein intake. This aims to reduce the build-up of urea in the blood (uraemia). Uraemia can make you feel quite unwell.

Once you start on dialysis you may need to increase your protein intake a bit, as some protein is lost in the dialysis fluid. This happens more if you have peritoneal dialysis rather than haemodialysis.

Fluid

If you are on haemodialysis, your daily fluid intake should be what you pass in urine (generally very little) plus 500 ml.

Peritoneal dialysis is a bit more flexible. However, you should usually have about 750 ml per day on top of the volume of urine you produce.

Your doctor or dietician should tell you how much your fluid intake should be.

Vitamins

Soluble vitamins (B and C) are lost in dialysis fluid, so should be replaced with vitamin tablets.

Maintaining a healthy weight

You may need to increase your food intake when you are on dialysis, as it causes an increase in your body's energy needs. If you are having peritoneal dialysis, some sugar (glucose) is lost in the dialysis fluid. Specialist dieticians can help you to plan your diet whilst you are on dialysis.