Dietary Protein, BUN and Creatinine: What's the Connection?
If you have been told you have chronic kidney disease (CKD), you may be familiar with the lab values BUN and creatinine. BUN stands for blood urea nitrogen. It is a measure of how much urea is present in the blood. Urea is a waste product of protein breakdown. Normal functioning kidneys are able to remove urea from the blood through making urine.
However, when kidney damage has occurred, BUN and creatinine levels become elevated. Similar to BUN, creatinine is a waste product of muscle breakdown. It is removed by healthy kidneys through urination. Both BUN and creatinine are lab tests used to identify if kidney damage has occurred.
In people with CKD, eating a high protein diet can contribute to elevation of BUN and creatinine. This is because these lab markers are involved with protein intake and protein stores in the body. The damaged kidneys are unable to remove excess amounts from the blood. For these reasons, restricting protein intake to about 0.6-0.8 grams per kilogram of body weight can be an effective way to slow the progression of CKD in some individuals. An person weighing 150 pounds (divided by 2.2 pounds per kilogram = 68kg), for example, would be recommended to limit protein intake to between 40-54 grams per day.
Some high protein foods that are commonly eaten include:
- Chicken, 3oz (28 grams of protein)
- Beef, 3oz (26 grams)
- Pork, 3oz (22 grams)
- Fish, 3oz (22 grams)
- Shellfish, 3oz (15-20 grams)
- Egg, 1 whole (6-7 grams)
- Beans, all varieties, 1/2 cup (7-9 grams)
- Lentils, 1/2 cup (9 grams)
- Nuts, 1oz (4-7 grams)
- Greek yogurt, 6oz (18 grams)
- Cottage cheese, 4oz (14 grams)
- Cow’s milk, 1 cup (8 grams)
Glomerular Filtration Rate
Glomerular Filtration Rate (GFR) is another lab value you may see. It is a measure of kidney function. GFR determines the rate at which your kidneys are filtering blood. The result is used to identify what stage of kidney failure you are experiencing. There are 5 stages of kidney failure; stage 1 is mild and stage 5 is end stage kidney disease.
If you know your creatinine level, you can use DaVita’s online GFR calculator to calculate and track your GFR . When GFR levels fall below 15mL/minute, dialysis is needed. If you or someone you know has CKD, following a protein-restricted diet may be an effective and simple way to help slow the progression to dialysis. Always check with your kidney doctor and dietitian before making changes in your diet.
For more information on interpretation of lab results, read “Understanding your Lab Work.”