The oxalic acid content of string beans is relatively high. Oxalic acid and calcium ions in the body can form calcium oxalate, calcium oxalate long time accumulation of easy to form stones, urinary stones and other diseases, can also lead to serious low calcium, low zinc anemia, in the long run can cause bone, teeth, mental retardation and other problems. And four season beans oxalic acid content is relatively high, do not recommend too much food. In addition, oxalic acid-rich foods are spinach, amaranth, cabbage, mustard greens, fungus, leeks, onions, wild rice, bamboo shoots and so on. Therefore, in order to prevent the formation of calcium oxalate stones, hypocalcemia, and hypozincemia, it is necessary to pay attention to adjusting the structure of the diet and reducing the consumption of foods rich in oxalic acid.