The oxalic acid in spinach reduces the bioavailability of mineral elements, and in the human body it is easy to form calcium oxalate with calcium ions leading to kidney stones, so oxalic acid is often regarded as an antagonist of the absorption and utilization of mineral elements. Cooking spinach can not be put together with tofu is this reason.

Oxalic acid root has a strong cooperating effect, when oxalic acid and some alkaline earth metal elements combined, its solubility is greatly reduced, such as calcium oxalate is almost insoluble in water. Therefore the presence of oxalic acid has a great influence on the bioeffectiveness of must minerals; when oxalic acid is combined with some transitional metal elements, due to the cooperating effect of oxalic acid, soluble complexes are formed, and their solubility is greatly increased.