Protein and your kidneys

Our kidneys are the filters of the body. When blood passes through the kidneys, fluid and minerals return to the body, and waste material is passed out with the urine. When you have chronic kidney disease (CKD), the ability to get rid of waste from the food you eat or drink is lost, and the waste starts to build up in your blood.

A kidney-friendly or renal diet helps minimize the amount of waste in the blood and decreases the amount of work the kidneys have to do. Protein, sodium, potassium and phosphorus are the main considerations of a renal diet.

If you have CKD, eating too much protein can irreversibly damage your kidneys. If your laboratory tests show that you have protein in your urine (proteinuria) or high blood urea nitrogen (BUN) levels, or both, eating less protein becomes very important.

Protein can come from animal sources – like beef, pork, poultry, eggs, fish, shellfish and dairy products – and plant sources, including beans, legumes and tofu. Protein powder supplements are usually made from whey or soy and are not recommended in a low-protein diet.

How much protein you need is determined by your stage of kidney disease, your weight, your urine protein results, whether or not you have diabetes, and your nutritional status. In general, CKD patients should limit their protein to about 0.8 grams of protein per kilogram of your ideal body weight. For example: if your ideal body weight is 60 kg, your protein needs are: 60 kg x 0.8 g/kg = 48 grams of protein or less per day.

If your kidney function continues to decline further, limiting protein to 0.55-60 grams per kilogram of your body weight can help delay worsening of your kidney function. It can also help to get more plant-based proteins or to switch to a completely plant-based diet, as plants proteins break down to less urea than animal proteins. Protein also exists in limited amounts in fruits, starchy foods and grains (including rice), so that needs to be accounted for as well.

Some common foods and their protein content per serving (about 100 grams/serving):

Bananas – 1.1 grams

Beef – 28 grams

Bread – 9 grams

Chicken breast without skin – 32 grams

Egg – 12 grams

Oranges – 0.9 grams

Pork – 27 grams

Rice – 2.7 grams

Salmon – 25 grams

Shrimp – 17 grams

Tilapia – 26 grams

Despite reducing protein intake, it’s essential to consume sufficient calories from other food groups to prevent weight loss and muscle wasting. In addition to managing protein intake, you will need to be aware of other dietary factors, particularly if you also have conditions like diabetes, high blood pressure, or elevated cholesterol levels. Medications may also need to be adjusted with changes in your diet.

Sometimes your doctor may prescribe keto acid analogues (ketoanalogues) to meet protein requirements of a very low-protein diet to prevent malnutrition. These should be taken in appropriate doses (about four to eight) tablets three times a day) to get enough amino acids to make up for the loss of protein in the diet. These ketoanalogues do not affect kidney function, and neither do they treat or cure CKD. If you are still eating a lot of protein, taking ketoanalogues will not give any added benefit to your health.

Restricting protein in the diet may slow the progression of CKD and delay dialysis for several years, although it is not clear if the benefits of protein restriction are worth the difficulty of sticking to a low-protein diet, particularly when there are other medications that can be used to slow the progression of CKD.

If you have CKD, talk to to your health care provider about the advantages and disadvantages of a low-protein diet, and how to maintain a proper diet for optimal health.