Neural tube defects in babies have decreased significantly since the federal government mandated that folic acid be added to enriched grains, a new study shows, but critics say preventable cases still occur because the fortification level is too low.
Folic acid deficiency is considered the major cause of neural tube defects, including spina bifida, an open spine that often leads to paralysis and other complications; and anencephaly, a condition in which part of the brain is missing. Folic acid, the synthetic form of folate, is a member of the B family of vitamins.
In 1998, the U.S. Food and Drug Administration required certain grains, breads and flour labeled "enriched" to be fortified with enough folate to supply a woman with an average of 100 micrograms of the vitamin each day.
That amount is much smaller than the 400 micrograms some experts say would be necessary to prevent 50 percent to 70 percent of neural tube defects.
"It is a tragic failure of public policy, both in the U.S. and around the world, that a single case of folic acid-preventable spina bifida and anencephaly occurs," Dr. Robert Brent of Thomas Jefferson University and Dr. Godfrey Oakley of Emory University wrote in a commentary in the current issue of the journal Pediatrics.
In the same issue, Pediatrics published a study based on data from 21 state health departments showing that in 2002 the rate of neural tube defects was significantly lower than the rate before folic acid fortification was required.
The rate declined 36 percent among Hispanics, 34 percent among whites and 19 percent among blacks, who have the lowest risk of neural tube defects, researchers from the Centers for Disease Control and Prevention's National Center on Birth Defects and Developmental Disabilities reported.
"Our study has shown that there really has been a positive impact from fortification," said Dr. Sonja A. Rasmussen, a clinical geneticist who headed the CDC study. "We need to assess the current level, which is what we're doing, and also to determine whether more folic acid would have an additional benefit in reducing neural tube defects."
A CDC study last year showed that the number of babies born with these defects dropped from 4,000 per year to 3,000 per year after folic acid was added to enriched grain.
Brent said the CDC estimates that 2,000 additional neural tube defects could be prevented if all women of child-bearing age were to get 400 micrograms of folic acid daily from enriched flour, vitamin supplements and the folic acid content of some foods.
"The Pediatrics study shows that while we're getting some effect because we fortified, we're not getting the maximum effect that we could, and, therefore, hundreds and hundreds of babies are being born with neural tube defects because their mothers lack sufficient folic acid," said Dr. Jennifer Howse, president of the March of Dimes, which focuses on preventing birth defects and infant mortality.
The FDA originally set a low limit for folic acid fortification because of concerns that higher doses could mask vitamin B12 deficiency. Folic acid corrects the anemia associated with low B12, a condition some doctors have used to diagnose the deficiency. In addition to anemia, a B12 deficiency can cause neurological problems.
But, Rasmussen said, a recent study by Dr. James Mills of the National Institutes of Health found that the current level of folic acid fortification does not mask B12 deficiencies.
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