This page deals with What's In Food. To learn about diet at different stages of renal disease, click on these links:
| For The Kidney | |
| On Haemodialysis | |
| On Peritonal Dialysis | |
| After Transplant |
What's in food?
Kidney function is essential in dealing with the waste material from ingested food - urea is made from dietary protein and is excreted by the kidneys along with other substances such as sodium, potassium and phosphate. |
Impaired renal function can lead to a build-up of these substances in the body. |
Dietary restriction can modify this accumulation and its effects. |
| Protein | Sodium | Potassium |
| Fluid intake | Phosphate | Energy |
| Fibre | Diet after Transplant |
Protein
Excessive intake of protein must be avoided, and sometimes protein restriction is advised for patients with renal failure. Here are the reasons:
| lowering protein intake may slow down the rate at which the kidneys get worse | |
| it reduces the phosphate load (important to prevent bone and other problems in the future) | |
| it helps to control the acid level in the blood - if the blood is too acid it can lead to loss of muscle and to a high potassium level in the blood | |
| in advanced (stages 4 and 5) kidney disease it can relieve symptoms such as nausea and vomiting |
It is recomended to most patients that a protein restriction is not imposed as it can interfere with eating a healthy diet. Read more about diet for the failing kidney.
On haemodialysis protein restriction is not generally required once patients are established and patients should eat a normal protein intake of 1 g/kg ideal body weight, about 70g each day. Read more about diet on haemodialysis.
In CAPD a higher protein intake is recommended due to a small loss of protein from the drained fluid (dialysate) which adds up to 5-10g over the day. It has been suggested that as much as 1.5g/kg of protein daily should be consumed but this is very difficult to achieve. An intake of 1.1-1.2g/kg ideal body weight is more realistic. Read more about diet on CAPD.
| A typical daily intake in the UK is 60 - 80g. |
| Normal requirement is only 45-55g |
| The richest sources are: Animal protein - meat, fish, cheese, eggs and milk Vegetable protein - nuts,beans, pulses,soya milk |
Sodium
Common salt is sodium chloride. Very low sodium diets, with food being cooked salt-free, are never recommended in renal failure. The existence of excess fluid in the body (eg swollen ankles) and high blood pressure should be managed by some sodium restriction to 100mmol per day. This allows for salt to be used in cooking, but means avoidance of very salty foods, and avoiding the addition of salt to food after it has been cooked. Many blood pressure tablets only work properly if combined with a reduced salt intake.
On haemodialysis, restriction in the form of "No Added Salt" diet is necessary since a greater intake will result in poorly controlled blood pressure. Read more about diet on haemodialysis.
On CAPD, there is a "no added salt" restriction for the same reasons. Read more about diet on CAPD.
On dialysis too much salt leads to excessive thirst, difficulty in adhering to the fluid restriction and risk of excess fluid and high blood pressure. A number of salt substitutes are available but they consist mainly of potassium chloride and therefore salt substitutes are not usually suitable for patients with renal failure.
A typical daily intake in the UK is 150 - 200mmol (9-12g of salt, or 3-5g of sodium) |
Only around 10% of this is found in fresh food, the remainder is added as sodium chloride or sodium bicarbonate in cooking and food processing, and as table salt which may be sprinkled on the food after cooking. |
Sodium rich foods: cheese, bacon, ham, sausages, tinned meat eg.corned beef, meat + fish paste Oxo, Bovril, Marmite, salted butter & margarine, tinned vegetables, tinned & packet soups salted nuts & crisps, salty biscuits eg TUC, Cheddars |
Other sources of sodium: Effervescent pain-killers - may contain up to 20mmol sodium per tablet! Antacids and some other medicines |
Potassium
Potassium is not restricted routinely in patients on conservative treatment of renal failure.
Too much potassium in the blood (hyperkalaemia), often occurs for reasons other than dietary excess like too much acid in the blood. Sometimes dietary potassium may have to be restricted for instance in diabetics and those on ACE inhibitors, drugs with a name ending ...pril for control of high blood pressure.
On haemodialysis, potassium is reduced during each dialysis treatment then usually rises between treatments. It is felt that a pre-dialysis potassium of up to 6mmol/L is safe. Patients must be aware of all foods which are rich in potassium but no food needs to be avoided completely due to its high potassium content. Read more about diet on haemodialysis.
On CAPD, it is more common to have a low level of potassium in the blood (hypokalaemic) and require a high potassium intake. One of the main differences between the diets for haemodialysis and CAPD is the recommended intake of potassium. The continuous uptake of glucose from the dialysis fluid may influence potassium balance. Some patients still require potassium restriction in the same way as those on haemodialysis. Read more about diet on CAPD.
A typical daily intake in the UK can vary from 50 to 150mmol |
Potassium is always found in association with protein and therefore all the protein-rich foods, especially milk, contribute significantly to the daily intake of potassium |
Other rich sources of potassium are: Potatoes - especially baked, chips & crisps (boiling leaches out a lot of potassium); bananas, grapes, rhubarb, fresh grapefruit, fresh pineapple, Kiwi fruit,dried fruit eg currants, sultanas, dates, pure fruit juice including apple juice (even though fresh apples are low in potassium) tomatoes, butter beans, sweetcorn, mushrooms, beetroot, sprouts, leeks chocolate (plain contains less than milk) liquorice, fruit gums, coffee. Coca-Cola & diluting fruit squash contain negligible amounts of potassium. |
Fluid Intake
All drinks contain mostly water. Fluids refer to all drinks taken per day. Until the kidneys fail and dialysis is required, a fluid intake of 2 litres is encouraged - it is important to avoid dehydration as this can affect the kidney function.
On haemodialysis the fluid allowance for each patient needs to be quite strictly controlled. Read more about diet on haemodialysis.
The optimum fluid allowance when on CAPD is more difficult to calculate. The amount of fluid removed varies from person to person and sometimes CAPD is not suitable, due to poor fluid removal (ultrafiltration). A typical fluid allowance on CAPD is 1 litre per day. Read more about diet on CAPD.
Phosphate
Too much phosphate in the blood (hyperphosphataemia), is usually only a problem in the later stages of renal failure although phosphate retention occurs long before it shows up in raised blood levels. The renal diet is automatically low in phosphate due to the protein restriction and if the phosphate rises above the upper limit of the normal range it can only be treated by using phosphate binding medication before meals. This medication works by binding phosphate in the gut and it is therefore important that it is taken just before food.
The commonest binders are calcium acetate (Phosex) or calcium carbonate (Calcium 500 or Calcichew), or sevelamer (Renagel). Renagel is a modern alternative but it is expensive and requires a lot of tablets.
On dialysis phosphate is controlled to a certain extent by diet. Phosphate binders are used in the same way as prior to dialysis with the aim of acheiving a pre-dialysis level of 1.5-2mmol/L.
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A typical daily intake of phosphorus in the UK is 35-40mmol |
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Phosphate, like potassium, is found in association with protein, especially in milk and cheese. Only a few other foods which contain phosphate like wholegrain cereals (wholemeal flour and bread, oatcakes). Other sources are convenience foods which have phosphates added by the food manufacturers. |
Energy
It is essential that patients on a protein restriction take a high energy diet. Too few calories lead to the breakdown of muscle to provide energy. This results in an increase in the blood urea and a debilitated patient.
A high calorie diet should be achieved through high energy foods such as sugar, jam, marmalade etc. but in some cases it is necessary to provide specialised products which are produced commercially.
Fibre
The intake of fibre is encouraged to avoid constipation. This can be important in CAPD as constipation can cause problems with the catheter position and result in poor drainage of dialysate.
Diet after Transplantation
A successful transplant allows dietary freedom, but in particular freedom to drink. A healthy diet is encouraged with avoidance of excessive use of salt or sugar along with high fibre and low fat - the latter is important due to the high cholesterol and other lipids frequently found in blood testing of transplant patients. It is also important to maintain a healthy weight. Read more about diet after renal transplantation.
Please be aware that while we have made all effort to ensure that this information is accurate, we cannot guarantee that there are no mistakes. Also that the best management for individual patients may differ from that outlined here. Only the doctors caring for the patient will be able to advise on this.
