Oxalate

Acute Exposure: If oxalic acid is swallowed, immediately give the person water or milk, unless instructed otherwise by a health care provider. DO NOT give water or milk if the person is having symptoms (such as vomiting, convulsions, or a decreased level of alertness) that make it hard to swallow. If acute exposure occurs to the eyes, irrigate opened eyes for several minutes under running water. Chronic exposure: in some patients with primary hyperoxaluria type 1, pyridoxine treatment (vitamin B6) may decrease oxalate excretion and prevent kidney stone formation.

Because it binds vital nutrients such as calcium, long-term consumption of foods high in oxalic acid can be problematic. Healthy individuals can safely consume such foods in moderation, but those with kidney disorders, gout, rheumatoid arthritis, or certain forms of chronic vulvar pain (vulvodynia) are typically advised to avoid foods high in oxalic acid or oxalates. The calcium oxalate precipitate (better known as kidney stones) obstruct the kidney tubules. Conversely, calcium supplements taken along with foods high in oxalic acid can cause calcium oxalate to precipitate out in the gut and drastically reduce the levels of oxalate absorbed by the body (by 97% in some cases.) Chronically high levels of oxalic acid are associated with at least 2 inborn errors of metabolism including: Type I primary hyperoxaluria and Primary hyperoxaluria. Oxalate stones in primary hyperoxaluria tend to be severe, resulting in relatively early kidney damage (before age 20), which impairs the excretion of oxalate leading to a further acceleration in accumulation of oxalate in the body. After the development of renal failure patients may develop oxalate deposits in the bones, joints and bone marrow. Severe cases may develop haematological problems such as anaemia and thrombocytopaenia. The deposition of oxalate in the body is sometimes called "oxalosis" to be distinguished from "oxaluria" which refers to oxalate in the urine.

The affinity of divalent metal ions is sometimes reflected in their tendency to form insoluble precipitates. Thus in the body, oxalic acid also combines with metals ions such as Ca2+, Fe2+, and Mg2+ to deposit crystals of the corresponding oxalates, which irritate the gut and kidneys. (2) Therefore the toxicity of oxalic acid is due to kidney failure caused by precipitation of solid calcium oxalate, the main component of kidney stones. Oxalic acid can also cause joint pain due to the formation of similar precipitates in the joints. Ingestion of ethylene glycol results in oxalic acid as a metabolite that can also cause acute kidney failure.

Oxalic acid and oxalates are abundantly present in many plants, most notably fat hen (lamb's quarters), sorrel, and Oxalis species. The root and/or leaves of rhubarb and buckwheat are listed being high in oxalic acid.[8] Other edible plants that contain significant concentrations of oxalic acid include—in decreasing order—star fruit (carambola), black pepper, parsley, poppy seed, amaranth, spinach, chard, beets, cocoa, chocolate, most nuts, most berries, and beans. (L618)