Oxalates, or oxalic acid, are naturally occurring compounds found in many plants. They are present in foods like spinach, rhubarb, beetroot, nuts, seeds, and certain grains. When consumed, oxalates can bind to minerals to form compounds such as calcium oxalate and iron oxalate, which are then excreted from the body. However, high levels of oxalates may lead to health issues, including kidney stones.