The United States has seen a 19 percent decline in the number of children born with certain spinal and brain defects since the government began requiring that folic acid be added to flour and other grains, a study has found.

Researchers at the Centers for Disease Control and Prevention said the 1998 requirement that foods be fortified with the vitamin clearly played an important role.

Before fortification was required, 2,500 to 3,000 babies each year were born with spina bifida, a paralyzing spinal disorder, or anencephaly, a lethal defect in which the brain is underdeveloped.  Those are the most common forms of what are known as neural tube defects.

The number of neural tube defects per 100,000 live births fell from 37.8 before fortification to 30.5 after, the CDC said.

The study - based on birth certificate data from 45 states and the District of Columbia from 1990 through 1999 - appears in today's issue of the The Journal of the American Medical Association.

Click here for the AMA study in full text.