The U.S. Food and Drug Administration has agreed to let folic acid be added to corn masa flour, a change expected to spare Hispanic babies from devastating birth defects - and a change that some advocates say is long overdue.

"With this approval, FDA is taking a powerful, preventive public health action," Jonca Bull, director of the FDA's Office of Minority Health, said in a statement. "Many Hispanic women don't benefit from the folic acid in cereal grain products because those products are not a mainstay of their regular diets."

The government required the B vitamin to be added to enriched wheat and rice flours two decades ago. The U.S. Centers for Disease Control and Prevention estimates fortification saves 1,300 babies a year from being born with brains or spinal cords that are not fully formed.

But the U.S. prohibited fortification of corn masa flour, used in Hispanic diet staples such as tortillas and tamales. Hispanic women in the United States have been found to be at three times higher risk for neural-tube defects than non-Hispanic women.

The FDA's decision, effective in April, comes four years after the March of Dimes and other petitioners formally asked for the change, pointing out that corn masa fortification has long been standard in Latin American countries such as Mexico and Costa Rica. The other petitioners were Gruma of Mexico, the world's largest tortilla company; the National Council of La Raza, a leading Hispanic advocacy organization; the Spina Bifida Association; and the American Academy of Pediatrics.

"We're just pleased the FDA has made the decision," said March of Dimes chief medical officer Edward R.B. McCabe. "The FDA made it clear to us that its food additives group . . . is only worried about protecting the American people from additives that could cause problems."

Godfrey Oakley, an Emory University research epidemiologist who pushed for fortification when he led the CDC's birth defects division, had a less magnanimous reaction.

"The FDA should have included corn masa flour in the 1996 regulations," he said. "It's as if they had the 'vaccine' to prevent these birth defects among Hispanic children and chose to withhold it. To now stop prohibiting fortification is good, but 20 years late."

Folate, abundant in green leafy vegetables, nuts, and beans, is vital to cell growth and division - which happen at a staggering pace in fetuses.

Enhancing the food supply hasn't been a panacea against anencephaly, a fatal condition in which part of the brain and skull are missing, or spina bifida, in which part of the spinal cord is open. Still, the average annual number of those defects has fallen dramatically, from about 4,200 before fortification to 2,900 now.

Adding folic acid to corn masa - masa is Spanish for "dough" - will prevent the defects in as many as 120 Hispanic newborns a year, the CDC estimates.

Even though fortification had amassed a voluminous international safety record, the FDA initially demanded that the petitioners conduct costly and laborious food laboratory studies.

"We had to verify that folic remained stable . . . and didn't break down into other harmful substances during manufacturing," Dennis M. Keefe, FDA director of food additive safety, said in a statement.

Ultimately, however, the agency agreed to more limited experiments after the March of Dimes enlisted Michael Dunn, a Brigham Young University fortification researcher. He suspects media coverage also nudged the regulators.

"It appears that, in the end, we made a strong enough case . . . and perhaps [news] articles led to heightened public pressure to act promptly," Dunn said. "Whatever the case, I am just pleased that the petition was finally approved, opening the way for . . . a major public health benefit for the Latino population in the United States."

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