The U.S. Public Health Service recommended yesterday that all women of childbearing age should take extra folic acid, a B vitamin, to prevent neural tube defects that affect 1 to 2 of every 1,000 babies born each year. The effects of these birth defects include paralysis and death.
Researchers on birth defects and nutrition said that if the advice was followed the incidence of neural tube defects like spina bifida and anencephaly should fall to between a quarter and a half of the current figure of 2,300 cases a year.
The women were urged to take 0.4 milligrams of folic acid a day. Women on average consume just half of that amount, said Dr. Irwin Rosenberg, a professor of medicine and nutrition at Tufts University in Boston.
Dr. Steven Laubacher, the executive director of the Spina Bifida Association of America, said: "At our organization, we try to discipline ourselves to be reserved. But this points in the direction of a major, major breakthrough."
Mr. Rosenberg said, "I think this is going to be precedent setting in respect to the whole business of health claims, supplements and fortification." He added, "Let's hope it comes out right."
Neural tube defects include anencephaly, in which most of the brain is missing, and spina bifida, in which a piece of the spinal cord protrudes from the spinal column, causing paralysis of parts of the lower body.
Spina bifida also may be accompanied by hydrocephaly, in which fluid fails to drain properly from the skull, a condition that can result in mental retardation.
Although many researchers had long suspected that folic acid was linked to neural tube defects, the new consensus that folic acid supplements can prevent many of these birth defects was speeded last spring by new results from a Hungarian study.
Like the final drop of water that makes a cup flow over, these data, on top of a growing pool of other results, were finally enough for some wavering researchers, said Dr. James Mills, the chief of pediatric epidemiology at the National Institute of Child Health and Human Development in Bethesda.
The Hungarian study, whose results were announced at a meeting last spring but have not been published, was a randomized controlled study of women who had not had a previous child with a neural tube defect. It showed that low doses of folic acid can prevent neural tube defects in these women. "It was very persuasive," Mr. Mills said. "It tipped the scales."
The new advice was formulated by scientists who met at the Centers for Disease Control on July 27, said Dr. Godfrey Oakley, who directs research on birth defects at the disease centers in Atlanta.
But the advice raises a thorny question: How are women supposed to get this folic acid?
It is not enough to tell them to take the vitamin after they are pregnant because the birth defects occur when the fetus' spinal column is fusing, at about two weeks after the first missed menstrual period. Many women do not even know they are pregnant at that time, which is why they are advised to consume the folic acid if they are even capable of becoming pregnant.
Vegetables like spinach and broccoli are especially rich in folic acid. But a lot of vegetables must been eaten to ingest 0.4 milligrams of folic acid a day, which is about twice the amount recommended by the National Academy of Sciences for men and women aged 15 to 50.
Women would have to eat about one and a half cups of boiled spinach to get the recommended amount of folic acid, and many people just do not eat green vegetables in such doses.
Another possibility is to fortify foods, in much the same way that vitamin D is added to milk to prevent rickets and iodine is added to salt to prevent goiters.
The Spina Bifida Association and leading researchers, including Dr. Aubrey Milunsky of Boston University, urge this course. But Dr. David A. Kessler, commissioner of the Food and Drug Administration, says he is undecided.
"That's an issue we need to confront as an agency," Mr. Kessler said. He said he was hesitant to take such a course because folic acid supplements can mask pernicious anemia, a disorder mainly of older people. "By doing good, we don't want to do harm," he said. He added that he is concerned about evaluating health claims by food manufacturers. "Where does a drug stop and a food begin?" he said.