Kidney function is essential in dealing with the waste material from digested food and the working body. As kidney function worsens, it may be necessary to alter diet to reduce the problems caused by these substances accumulating. Control of diet is also necessary in patients on dialysis (see other sections linked from the Diet Home page), as dialysis only partly replaces kidney function. Finally, many patients with advanced kidney disease lose their appetite and risk becoming undernourished.
In the past a low protein diet was often recommended to slow down the steady deterioration of kidney function that occurs in some patients. We don't advise this any more, instead recommending a controlled protein diet (not low, not high; 0.8-1g protein per kg of ideal body weight, if you like measuring).
Why not low protein?
- Modern treatments, especially improved blood pressure treatments, have made any extra benefit from low protein diets much smaller.
- Low protein diets don't taste good, and are very difficult to follow.
- There is a significant risk of long-term malnutrition in those on low-protein diets.
- People are often started on dialysis sooner as they tend to do better therefore low protein diets are not as beneficial.
Why not high protein?
- High protein intake in CKD makes the blood more acid, and this can lead to increased muscle breakdown.
- High protein intake means high phosphate intake too (see below.
- In animals and probably humans, large amounts of protein may damage kidneys.
- High protein intake may increase feelings of nausea.
Protein supplements and high protein diets may be harmful if you have CKD
- Don't follow the Atkins diet or other high-protein diets for weight loss if you have CKD.
- Don't take protein supplements unless a renal dietitian agrees you need them
- Don't take creatine or similar supplements for muscle development.
Sometimes low protein diets are useful
In patients who do not want dialysis, or cannot have it for some reason, low protein diets may cut down symptoms, but advice and monitoring by a renal dietitian is essential to do this safely.
Common salt is sodium chloride. Keeping the amount you eat down is important for almost all patients with kidney disease, even at early stages. Too much salt causes high blood pressure and fluid retention (more info). Many blood pressure tablets only work properly if combined with a reduced salt intake.
In a very few people it is necessary to encourage a high salt intake - "salt wasters" are patients who pass large amounts of sodium in the urine. This happens in some kinds of kidney disease, and can cause serious salt and water depletion.
Potassium should not be restricted routinely, as it is present in many very healthy foods, however this is sometimes necessary when kidney function has become very poor. High potassium levels are very dangerous but usually only a problem in advanced kidney disease. Depending on medication some unlucky people need to restrict potassium at milder levels of kidney failure.
More info on potassium
Hyperkalaemia (too much potassium in the blood) can have other causes apart from eating too much potassium. For example some medicines, such as ACE inhibitors (drugs with a name ending -ipril) and ARBs (ending -sartan) raise blood potassium levels, and there can be other reasons. In some patients it may be better to continue the drug and watch your potassium intake, as these drugs can protect the kidneys particularly well.
Until end-stage is reached most patients benefit from maintaining a normal fluid intake (e.g. 1.5-2 litres daily). You should drink when you are thirsty, and avoid dehydration, which is bad for kidney function. However some patients have to limit their drinking when kidney function becomes poor (fluid restriction). NOTE: it is impossible to stop yourself from drinking if there is too much salt (sodium) in your diet - see above.
Hyperphosphataemia, too much phosphate in the blood tends to become a significant problem in the later stages of renal failure, although phosphate retention occurs long before it shows up in raised blood levels.
Avoiding excess protein limits the amount of phosphate in the diet too, and there are some foods that can be limited if the level of phosphate in blood rises. However in advanced kidney failure most people require phosphate binding medication before meals. This works by binding phosphate in the gut and preventing it from being absorbed into the body. It is therefore important that it is taken with or just before food. These are medicines such as calcium acetate or carbonate sevelamer, Lanthanum carbonate. (Trade names include Renagel, Fosrenol, Phosex, Phoslo, Renvela, Osvaren, Renacet and Calcichew).
Too few calories leads to the breakdown of muscle to provide an energy source - this will lead to malnutrition and contributes to make patients more prone to infections and less able to do daily activities.
As kidney failure gets worse, people tend to eat less, and under nutrition can become a major problem. Sometimes it is necessary to provide dietary supplements if the patient can't eat enough.
More info about undernutrition and energy intake
Diabetes and Chronic renal failure
This is a common combination and renal dietitians will be familiar with the dietary challenges this creates.
Acknowledgements: The authors of this page were Elizabeth Sloan, Hazel Elliott and Susan Reed. It was first published in January 2001 and extensively revised in August 2006 then reviewed again by Susan Reed in August 2013. The date is was last modified is shown in the footer.