Protein is responsible for repairing tissue, manufacturing essential enzymes and hormones, providing energy, and supporting bodily growth. This nutrient can be found in a variety of dietary sources such as meats, milk, nuts, fish and poultry. Protein is often touted as a muscle-building supplement, and while adequate protein consumption can support lean muscle mass growth, excessive amounts of protein can potentially cause kidney damage among those with preexisting kidney disorders.
Recommended Protein Intake
The McKinley Health Center says the USDA Dietary Reference Intake suggests you consume 10 to 35 percent of your daily calories from protein sources. For example, if you consume a 2,000-calorie diet, approximately 200 to 700 calories should come from a protein source such as meats, dairy or nuts.
High Intake Levels
The September 2005 issue of the “Nutrition & Metabolism” journal reports there is no solid scientific data outlining an exact upper limit intake of protein. Even though there is no official “overdose” limit of protein available, the “Nutrition & Metabolism” journal suggests 1.5 grams of protein per 2.2 pounds of body weight may cause detrimental effects among certain groups. Using this as a guide, a 160-pound man who consumes roughly 109 grams or more of protein per day could be at risk of developing adverse effects. However, talk with your doctor to obtain a protein upper intake level based on your physical health.
Protein and Your Kidneys
As protein enters your digestive system, it is separated from other compounds and introduced into your bloodstream. When blood passes through your kidneys, waste is filtered through tiny blood vessels known as glomeruli. This filtering action, also known as glomerular filtration rate, or GFR, removes harmful waste, leaving protein and healthy cells in your bloodstream. Although researchers at the National Kidney & Urologic Diseases Information Clearinghouse are unsure exactly how dietary protein and cholesterol affect kidney function, consuming more than the recommended amount of protein seems to increase glomerular pressure and hyperfiltration, which is defined as rapid filtration and fluid re-absorption. Increased glomerular pressure may cause a significant increase in urine production, which has the potential of causing dehydration.
Effects of Protein
Although scientific evidence proves an increase in dietary protein also increases hyperfiltration and GFR, solid scientific data is lacking to determine if protein consumption directly causes or progresses kidney disease or disorders in healthy individuals. Even though GFR activity is enhanced with excess protein intake, this elevated activity does not seem to be detrimental among healthy adults. The October 2004 issue of the “Journal of the Society for Gynecologic Investigation” found healthy pregnant women can have an 85 percent increase in GFR activity without experiencing any adverse reactions. Ergo, inordinate protein consumption may not cause kidney disorders or problems in healthy adults. However, Katherine Zeratsky, R.D., L.D. reports on MayoClinic.com that high-protein intake has the possibility of worsening kidney problems among those with a preexisting kidney disorder.
References
- McKinley Health Center; Macronutrients: The Importance of Carbohydrate, Protein, and Fat; March 2008
- MayoClinic.com; Are High-Protein Diets Safe for Weight Loss?; Katherine Zeratksy, R.D., L.D.; June 2010
- Harvard University Gazette: Too Much Protein May Cause Reduced Kidney Function
- “Nutrition & Metabolism” Journal; Dietary Protein Intake and Renal Function; William F. Martin, et al.; September 2005
- National Kidney & Urologic Diseases Information Clearinghouse; The Kidneys and How They Work; September 2010
- “Journal of the Society for Gynecologic Investigation”; Mechanisms of Renal Vasodilation and Hyperfiltration During Pregnancy; K.P. Conrad; October 2004
- Similima; Glomerular Filtration; K. Bindu, BHMS, M.D.
- Australian and New Zealand College of Perfusionists; Glomerular Filtration Rate; K.C. Potger; 2001
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