BOSTON — This much at least is certain: Americans eat far more folic acid than ever before, whether they know it or not.
For the last year and a half, everyone who lives on sandwiches, toast, pizza, pasta and just about anything else made from flour or rice has ingested a little extra dose of this essential B vitamin.
Fortification, it's called. But beyond the reasonably clear evidence that vitamin levels have risen in our bloodstreams, the big questions remain: Are we better off as a result? Does it make healthier babies at the start of life? Or healthier hearts later on?
Folic acid fortification began in January 1998 under orders from the Food and Drug Administration. Food makers must add 140 micrograms of folic acid to every 100 grams of flour, rice, pasta and cornmeal. This is in addition to the extra thiamine, riboflavin, niacin and iron they already put in.
In a way, the entire U.S. population set out that month on a medical experiment. Its likely outcome is the subject of spirited, even angry, disagreement. Some contend it will prevent many serious birth defects; others predict a minimal effect. In truth, no one knows how much good will come of this or whether it might even cause some unanticipated harm, as unlikely as it seems to most experts.
The goal is to prevent two forms of birth defects, anencephaly and spina bifida. Babies with anencephaly have no brains, and they usually are born dead or die soon after birth. Those with spina bifida have defective spinal columns. Their disabilities can range from scoliosis, a sideways bending of the spine, to mental retardation and paralysis.
The Centers for Disease Control and Prevention in Atlanta estimates that 4,000 U.S. pregnancies each year have these conditions. Since the defects can be found with prenatal tests, many end with abortions. But each year about 2,500 babies are born with them.
Evidence has accumulated for several years that extra folic acid, sometimes called folate, can often prevent these defects. No one knows for sure how much is needed beyond the folate naturally found in orange juice, green leafy vegetables and other foods. But studies have shown that women who take multivitamins, which contain 400 micrograms of folic acid, reduce the risk by half or more.
After long debate, the FDA decided to add enough folic acid to the food supply so the average American, including women of childbearing age, will consume roughly an extra 100 milligrams daily. This is the amount of folic acid in three slices of bread.
Some, including the March of Dimes and factions within the CDC, argued unsuccessfully that this is only one-quarter of the optimal amount needed to prevent birth defects. Those who won the argument maintain that anything more carries the risk of hazardous vitamin levels. Too much folic acid could mask anemia, a key symptom of vitamin B-12 deficiency. Left untreated, B-12 deficiency may cause severe nerve damage.
For it to work, folic acid supplements must be taken in the first weeks of babies' development in the womb, a time when many women do not realize they are pregnant. Because bread alone may not give women enough folic acid, the March of Dimes started a $10-million campaign in January to encourage use of multivitamins, which only about one-third of women of childbearing age take.
For now, the only clear evidence of fortification's effects is from the Framingham Heart Study in suburban Boston. Doctors there checked blood samples taken from 1,006 volunteers before and after fortification. The results are encouraging.
Average folic acid levels doubled after fortification. And folate deficiency nearly disappeared, falling from nearly a quarter of the volunteers to less than 2%.
Furthermore, their levels of homocysteine, a byproduct of food metabolism, dropped about 7%. No one knows exactly what this will mean, but it could be especially good news. Experts have long noticed that people with high homocysteine levels are unusually likely to develop heart trouble. Still, there is no evidence yet that lowering homocysteine will reduce this risk.
"It looks as though the dose the FDA picked was pretty good," says Dr. Irwin H. Rosenberg of Tufts University, the study's senior author. "Those who say it should be three or four times that much need to come up with some evidence."
However, March of Dimes officials and others note that the Framingham volunteers are largely white, middle-aged and middle class. While fortified foods are inescapable, young women--especially those of other races--may eat less of them. And even if they do consume as much as the Framingham folks, that may still not be enough to prevent birth defects.
"Knowing that food fortification is raising blood folates is like a rousing cheer along the race," says Dr. Donald B. Mattison, the March of Dimes medical director. "It's a reward for having taken the right steps, but it doesn't mean we've accomplished what we want to."