Side Effects of Oxalic Acid

Oxalic acid is a naturally occurring compound in many plant foods. It is used in industry as a bleaching agent and for rust removal. In your body, oxalic acid can combine with calcium in the kidneys to form kidney stones in susceptible people. Oxalic acid is poisonous when consumed in high quantities, so people with certain health conditions should avoid high oxalate foods.

Some vegetables, such as spinach, are high in oxalic acid. (Image: vkara/iStock/Getty Images)

Kidney Stones

Kidney stones are a major side effect of excess oxalic acid, according to a study conducted by scientists at the Department of Pharmacognosy, Ultra College of Pharmacy, Madurai, Tamil Nadu, India. In the study on laboratory animals, oxalic acid kidney stones were reduced by administration of the herb Salvadora persica, also known as peelu, toothbrush tree or mustard tree. Researchers found the herb to exert both preventive and curative effects. The study was published in the November 2010 issue of the journal "Methods and Findings in Experimental and Clinical Pharmacology."

Kidney Damage

Oxalic acid can cause kidney damage following a certain surgical procdure, according to a case study reported by researchers at the Departments of Nephrology and Renal Pathology, Evangelismos General Hospital, Athens, Greece, in the February 2011 issue of the journal "Clinical Nephrology." The patent had undergone a gastric bypass surgery for treatment of obesity and subsequently developed excess oxalic acid in the kidneys. Dialysis did not improve kidney function. Researchers hypothesize that the surgical procedure may lead to malabsorption of fats and increased fatty acids in the intestine. Calcium in the intestines, which normally binds to oxalate and prevents it from being absorbed, binds to the extra fatty acids. Oxalate is then absorbed into the bloodstream and accumulates in the kidneys as they attempt to filter the oxalate out of the bloodstream. A low fat and low oxalate diet is prescribed.

Vitamin C

Excess vitamin C consumption may lead to oxalic acid kidney stone formation, explains Sareen S. Gropper, co-author of the book "Advanced Nutrition and Human Metabolism." While oxalic acid is a product of the breakdown of vitamin C and may, theoretically, accumulate to form kidney stones, doses of as much as 10 g of vitamin C have not been associated with increased oxalate stone formation. Some experts caution that anyone who is at increased risk for forming calcium osalate stone should avoid high doses of vitamin C.

Poisoning

Oxalic acid is a poison that can cause a range of potentially life-threatening symptoms. John E. Duldner, Jr., M.D., of The University of Maryland Medical Center, lists abdominal pain, convulsions, kidney problems, low blood pressure, mouth and throat pain, shock, tremors, vomiting and weak pulse as possible signs of oxalic acid poisoning. First aid treatment includes drinking water or milk, unless the the person is experiencing symptoms that make it difficult to swallow, such as vomiting, convulsions or decreased alertness. Seek emergency care if these symptoms appear suddenly.