Folic acid is a B vitamin that plays a large role in a certain kind of chemical reaction called a one-carbon transfer, where a single carbon is taken from one chemical compound and added to another. One-carbon transfers are important for synthesizing some of the building blocks of DNA. They also help to regulate gene expression through the process of methylation, which involves adding single-carbon methyl groups to DNA. These biochemical processes are not only important in keeping adults healthy, but are also essential for healthy embryonic development. One major area where folate plays a role is in the development of the neural tube of the embryo.
The neural tube is an embryonic structure that is the precursor of the central nervous system, which includes the brain and spinal cord. Neural tube defects are a set of potentially serious problems which all involve the failure of the neural tube to close properly during development. One example is spina bifida, which affects the spinal cord.
In order to prevent neural tube defects, the recommended daily allowance for folic acid jumps from 400 micrograms per day for most adult men and women to 600 micrograms per day for pregnant women. Furthermore, the Centers for Disease Control and Prevention (CDC) emphasize the importance of all women of childbearing age getting at least 400 micrograms per day to prevent neural tube defects even in women who aren’t planning on getting pregnant, since almost half of pregnancies in the United States are unplanned.