Folic acid is a water-soluble vitamin and is an essential substance for cell growth and reproduction. If the body is deficient and low in folic acid, it can easily lead to neural tube abnormalities, megaloblastic anemia, cleft lip and palate, tumors and other diseases. The causes of low folic acid are the following: First, it is insufficient intake. Folic acid is present in many green leafy vegetables and fruits, such as spinach, kale, oranges, kiwi, etc.; it is also contained in animal liver, egg yolk and other foods, and if the diet is usually too partial, it will lead to insufficient intake of folic acid and deficiency. Secondly, malabsorption, because the folic acid that enters the body needs to be degraded into free folic acid before it can be absorbed, glutamyl carboxypeptidase, which has the ability to hydrolyze folic acid, exists in the epithelium of the small intestinal mucosa, and when small intestinal diseases cause changes in glutamyl carboxypeptidase, it will cause the digestion, distribution and absorption of folic acid to be affected, and low folic acid in the body will occur.