Protein supplements are found on health food store shelves and in some gyms specializing in weightlifting. Often taken by athletes trying to build muscle, these supplements can have a deleterious effect on kidney patients. Since kidney disease often goes undiagnosed, you should consult your doctor before embarking on any regimen that requires protein supplements.
Protein Requirements
The U.S. Department of Agriculture states that adults need 0.8 g of protein for every kilogram of body weight. This means that a 120 lb. woman needs approximately 44 g of protein every day. Most U.S. adults consume far more than this. For example, 8 oz. of nonfat fruit yogurt has 10.78 g of protein, or almost 25 percent of the daily requirement.
Kidney Functions
Healthy kidneys filter the blood. Among other things, they remove nitrogenous waste products from muscular activity. More than 200 gallons of blood are filtered every day. During the filtration process, kidneys keep protein in the blood and prevent it from spilling into the urine. Urine from healthy people contains no more than a trace of protein.
Urine Protein
High urine protein is a red flag for kidney disease. It often remains undetected until found on a life insurance exam or routine physical. This is unfortunate because high urine protein can damage kidneys. Proteins are large, complex molecules. They can damage the delicate filters of the kidney called glomeruli when they pass into the urine. If this happens for months or years, so many glomeruli can be lost that overall kidney function declines.
Protein Restriction
In some instances, nephrologists recommend that kidney patients limit their protein intake. The rationale for this recommendation is that urine protein can be minimized by limiting dietary protein. Protein supplements would be damaging for these patients because they increase urine protein levels. For this reason, most nephrologists recommend that patients such supplements.
Warning
Just as you should check with your doctor before taking protein supplements, you should also check with your nephrologist before embarking on protein restriction, because such a regimen is not for everyone. For example, protein restriction is never recommended for children or for patients in the final stages of kidney disease.
References
- USDA Nutrient Data Laboratory: Yogurt, fruit variety, nonfat
- USDA; Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids - Chapter 10; 2005
- National Kidney Foundation: How Your KIdneys Work
- National Institute for Diabetes and Digestive and Kidney Diseases: Proteinuria
