Why Fortify? Prevent Birth Defects of Brain and Spine
All people need folic acid (vitamin B9) to produce and maintain healthy cells and prevent folate deficiency anemia. Also, fortifying wheat flour with folic acid lowered plasma homocysteine levels in Australian adults.
Women especially need folic acid to reduce the risk of their children having birth defects of the brain and spine called neural tube defects (NTDs). These include spina bifida, anencephaly and encephalocele. They cause early death or lifelong disability.
In spina bifida, the baby’s spine does not form correctly. In mild cases, permanent loss of some sensation or movement occurs. Severe cases include paralysis and varying degrees of loss of bowel and bladder control. Children born with spina bifida will undergo a lifetime of surgeries and face many health issues. Spina bifida cannot be cured. (The illustration below is courtesy of the US Centers for Disease Control and Prevention (CDC).
With anencephaly, the brain does not form properly. Pregnancies affected by anencephaly are often miscarried. Babies born with anencephaly die shortly after birth.
With encephalocele, part of the brain protrudes through the skull. This is a rare birth defect.
Many birth defects of the brain and spine can be prevented if women have 400 micrograms of folic acid daily at least one month before conception and in the early stages of pregnancy .
Fortifying flour and rice increases folic acid intake without requiring consumers to change their behaviors. One meta-analysis showed that fortifying wheat flour with folic acid reduced the incidence of NTDs by an average of 46%. 
A baby’s neural tube forms within the first four weeks of pregnancy. If women wait until they learn they are pregnant to take folic acid supplements, the baby’s neural tube may already be formed. Then it is too late for folic acid to have the protective effect.
The March of Dimes estimates that more than 300,000 babies are born with an NTD every year for a global birth prevalence of 24/10,000 . Countries which track birth defects generally find that their NTD prevalence drops to less than 10 per 10,000 live births after they begin fortifying flour with folic acid .
Fortifying flour with folic acid is credited with preventing at least 35,500 of these birth defects a year or an average of 97 a day. Only about one-third of the world’s flour from industrial mills is fortified, however, so this is only 13% of the NTDs that might be prevented .
Some foods such as spinach and liver are rich in vitamin B9 which is called folate in unfortified foods. However, folate is not easily absorbed, making it "difficult for a woman to eat enough natural food folate to prevent neural tube defects" .
For example, to consume the recommended amount of food folate equivalents, a person would need to eat:
- 23 spears of cooked asparagus or
- 4 cups of cooked okra or
- 4 cups for raw spinach or
- 2 slices of beef liver or
- 6 cups of orange juice or
- 4.5 cups of cooked broccoli 
Some people have been told to avoid folic acid because they have a variation of the MTHFR (methyltetrahydrofolate reductase) enzyme. However, these individuals simply process folic acid more slowly than those without the variation. See the CDC recommendation for people with the MTHFR variation to continue taking folic acid.
A review of the safety of folic acid published in 2018 noted that, "Current folic acid fortification programs support public health in populations, and the exposure levels are informed by and adherent to the precautionary principle." Also see this literature review from December 2016.
For additional information, see Folate Status in Women and Neural Tube Defect Reduction, an open access special edition of the Annals of the New York Academy of Sciences.
 Facts About Folic Acid, U.S. Centers for Disease Control and Prevention
 Blencowe, Hannah et al. “Folic Acid to Reduce Neonatal Mortality from Neural Tube Disorders.” International Journal of Epidemiology 39.Suppl 1 2010.
 Global Report on Birth Defects, March of Dimes Birth Defects Foundation, 2006.
 Zimmerman, Sarah. Fifteen Years of Fortifying With Folic Acid: Birth Defects are Reduced and Healthcare Expenses are Averted. Sight and Life. 2011.
 Arth, Annelise, et al. 2012 A 2015 global update on folic acid-preventable spina bifida and anencephaly. Birth Defects Research (Part A): Clinical and Molecular Teratology. July 2016.
 Marchetta, C.M. et al., Assessing the association between natural food folate intake and blood folate concentrations: a systematic review and Bayesian meta-analysis of trials and observational studies. Nutrients. 2015.
 Suitor & Bailey., Dietary folate equivalents: Interpretation and application. Journal of the American Dietetic Association, 2000.