Fortification of food with folic acid to reduce the number of neural tube defects was
introduced 10 y ago in North America. Many countries are considering whether to adopt this
policy. When fortification is introduced, several hundred thousand people are exposed to an
increased intake of folic acid for each neural tube defect pregnancy that is prevented. Are
the benefits to the few outweighed by possible harm to some of the many exposed? In
animals, a folic acid–rich diet can influence DNA and histone methylation, which leads to …