People who already have a high risk of developing painful kidney stones due to genetics or illness may be at greater risk when they are following a low-carb diet, but studies have not conclusively shown that high-protein diets will induce stone formation in people with healthy kidneys.
Definition
Your urinary system filters wastes and excess water out of your system through the kidneys, ureter, bladder and urethra. Excess calcium, oxalate and phosphate are dissolved in the waste water for removal. Most of the time, your urine contains chemicals that keep dissolved minerals from forming crystals. When these chemicals don't do their job, tiny stones can form in the kidney, bladder or urethra.
Causes
According to the National Kidney and Urologic Diseases Information Clearinghouse, doctors don't always know why kidney stones form. A particular diet may cause one person to develop kidney stones, but have no effect on someone else. Ever since low-carb, high-protein diets became popular in the 1990s, health experts have argued about the possible impact of a high-protein diet on kidney stone formation. Research has not definitively shown that a low-carb diet increases kidney stone risk in healthy people with a properly functioning urinary system.
Research
MayoClinic.com says that low-carb diets can cause or worsen kidney problems because your body may have a hard time removing the byproducts a diet high in protein and fat. In 2002, S.T. Reddy wrote in "The American Journal of Kidney Disease" that after six weeks on a low-carb diet, study subjects showed increased risk for kidney stone formation.
Writing in 2005 in "Nutrition and Metabolism", William Martin, of the University of Connecticut and other researchers reviewed all the available literature about protein and kidney stones and found no direct link between high protein diets and kidney stones. Martin suggested that, in some people high protein levels may be tipping the balance when a person already has kidney problems.
Prevention
If you have already had a kidney stone, you are more likely to develop stones than a person who has never had one. You can make it easier for your body to dissolve waste products by providing ample fluids -- preferably water. Drink several quarts of water a day, especially if you are following a low-carb diet. Many people on carb-restricted diets use supplements to make up for nutrients missed by avoiding grains. Some supplements, like calcium, can make it difficult for your body to properly eliminate waste products. Talk to your doctor about the likely effects of a low-carb diet with your specific kidney history.
References
- National Kidney and Urologic Diseases Information Clearinghouse: Kidney Stones in Adults
- MayoClinic.com: Are High-Protein Diets Safe for Weight Loss?
- "The American Journal of Kidney Diseases": Effect of Low-Carbohydrate High-Protein Diets on Acid-Base Balance, Stone-Forming Propensity, and Calcium Metabolism: ST Reddy: Aug 2002.
- "Nutrition and Metabolism"; Dietary Protein Intake and Renal Function
