Oxalic acid seems to assist in the formation of crystals in the body by combining with calcium and various metals. (The precipitate is referred to as an oxalate.) Consequently oxalic acid also inhibits calcium absorption by the body. Even so, most of the foods that are high in oxalates have many beneficial effects that more than offset the downsides of the organic acid. Also, it is not currently known if oxalic acid has some other beneficial effect on the system.