It was all about the babies. A decade ago, when the U.S. required flour, bread and pasta to be fortified with folic acid, health experts believed it would help prevent devastating birth defects such as spina bifida.
There's no question that it worked. As many as 1,000 newborns a year in the United States - and many more elsewhere - have been spared so-called neural tube defects because their mothers got a crucial infusion of folic acid before they even knew they were pregnant.
But now some scientists are asking whether there have been unforeseen trade-offs for the population as a whole - including thousands of additional colon cancer cases each year, a somewhat smaller bump-up in prostate cancer, and an increase in cognitive impairment among the elderly.
"The existing science at the time this decision was made showed the benefits and not any significant risk," said Dr. Joel Mason, director of the Vitamins and Carcinogenesis Laboratory at the U.S. Department of Agriculture's Human Nutrition Research Center at Tufts University. "What has evolved is, there's an increasing level of concern that it might be harming some segments of the population."
The renewed debate comes at a time when activists in the United States are pushing to increase the amount of folic acid in fortified foods, under the theory that if some is good, then more is better.
It also comes as the United Kingdom has put on hold its effort to require folic acid fortification. Scientists there are considering new research suggesting a possible downside to adding folic acid to the national diet.
Not everyone is convinced there even is a debate. The benefits of folic acid have been clearly proved, they say, and if anything, women of childbearing age need more folic acid than fortified foods provide. Proponents say that in addition to deterring birth defects, folic acid might prevent some cancers, strokes and cardiovascular disease.
And any potential downsides, they argue, are unproven.
Dr. Walter Willett, chairman of the department of nutrition at the Harvard School of Public Health, said time will show that there are more benefits to folic acid than previously known - and not that it causes cancer.
Though scientists don't fully understand how folic acid works, they believe that it assists in the formation of the building blocks of DNA, stimulating cell growth, preventing damage and helping DNA to replicate.
