Oxalate is a substance produced in your liver and found in a wide variety of common foods. In some people, this substance combines with calcium in the urine and leads to the formation of crystalline structures called kidney stones. Oxalate is not poisonous, but if you eat too many foods high in oxalate, you can potentially increase your risks for kidney stone development.
Oxalate Basics
Oxalate is derived from another substance called oxalic acid and belongs to a class of molecules called salts. All salts are characterized by a neutral reading on the pH scale, which measures relative acidity. Your body doesn't appear to use oxalate for any vital purpose; under normal circumstances, more than 90 percent of the oxalate content in your system gets passed to the kidneys for elimination in your urine. Oxalate levels in your urine can increase abnormally if you eat too many oxalate-containing foods, if you absorb too much oxalate in your intestine, or if your liver produces too much of the substance.
Kidney Stone Formation
Normally, oxalate, calcium and other waste materials in your urine stay thoroughly dissolved and pass from your body with ease. However, in certain conditions, these materials can fall out of solution and form crystals that clump together in various sizes. These clumps of crystals are commonly referred to as kidney stones. Most kidney stones contain a combination of calcium and oxalate or calcium and another substance called phosphate, according to the National Kidney and Urologic Diseases Information Clearinghouse.
Oxalosis
In addition to contributing to the formation of certain types of kidney stones, high concentrations of oxalate in your urine can damage your kidneys themselves, the Oxalosis and Hyperoxaluria Foundation reports. If your kidneys receive enough damage, they will start to lose their ability to filter oxalate from your bloodstream. In turn, if your blood oxalate levels rise high enough, the calcium in your bloodstream can combine with oxalate and lead to the buildup of calcium oxalate crystals in tissues throughout your body. The technical term for this buildup is oxalosis.
Considerations
Roughly 20 percent of people with calcium oxalate kidney stones have too much oxalate in their urine and can potentially benefit from a low-oxalate diet, the University of Wisconsin-Madison explains. However, you can also develop these stones when oxalate levels in your urine are normal, and most people with calcium oxalate stones don't benefit from reduced oxalate intake. Oxalate-containing foods known to raise oxalate levels in urine include beets, rhubarb, spinach, wheat germ, okra, peanuts, sweet potatoes, chocolate, Swiss chard, black and green tea and strawberries. Consult your doctor for more information on oxalate consumption and kidney stones and other oxalate-related disorders.
References
- The Oxalosis and Hyperoxaluria Foundation: What Is Hyperoxaluria and Oxalosis?
- National Kidney and Urologic Diseases Information Clearinghouse: Kidney Stones in Adults; April 2007
- University of Wisconsin-Madison - School of Medicine and Public Health: Urology; Oxalate
- Biology Online: Oxalate
- Biology Online: Salt
