A vitamin of the vitamin B complex. In its active form, tetrahydrofolic acid, it is a coenzyme in various reactions involved in the metabolism of amino acids, purines, and pyrimidines. It is synthesized by intestinal bacteria and is widespread in food, especially green leafy vegetables. Deficiency causes poor growth and nutritional anaemia. Adequate dietary folic acid is essential for pregnant women to reduce the risk of neural tube defects, such as spina bifida, in the developing fetus.