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Oxalates, also known as Oxalic Acid, may be found in many types plants including leafy greens, fruits, cacao, nuts, and seeds.

In concentrated amounts, these oxalates can also crystalize into calcium oxalate, which is an irritating biomineral. Calcium oxalate can be found in any tissue or organ of plants, and may also form in mammals as kidney stones.

Insoluble calcium oxalate plays a critical role in regulating calcium concentration in plants.

Oxalates also provide the plant with a higher tolerance to aluminum toxicity for those that are growing in acidic soils. It is also a key factor in phytoremediation in soils that are considered toxic due to their lead, cadmium, zinc, or other heavy metal content as the plant can better process these soils.

Additionally, oxalates are a defense mechanism against grazing animals and pests as they perceive the substance as an irritating, glass-like substance when chewed or ingested.

Ingesting high levels of oxalates can cause internal bleeding, gastrointestinal distress, drooling, weakness and lethargy, or urinary trouble, eventually leading to kidney failure with repeated ingestion.

This substance is the main reason why many houseplants are considered toxic to pets and must be diagnosed and treated immediately at a veterinary clinic. It is also a significant problem in grazing animals that are allowed to graze un-adapted to local, oxalate-rich flora.

The substance is also present in many common foods such as rhubarb, coffee, dark green vegetables, and many others. Oxalic acid can, however, often be neutralized by boiling or steaming the vegetables.

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