Washington ? Baby-protecting folic acid is getting renewed attention: Not only does it fight spina bifida and some related abnormalities, new research shows it also may prevent premature birth and heart defects.

Now pregnancy specialists are asking whether it’s time for the government to boost the amount being added to certain foods to help ensure mothers-to-be get enough. But for older adults, there may be a down side to the nutrient: Extra-high levels late in life just might pose a cancer risk.

“Folate is assuming the role of a chameleon, if you will,” says Dr. Joel Mason of Tufts University’s nutrition research center, who is researching that possible risk.

Folic acid is an artificial version of folate, a B vitamin found in leafy green vegetables, citrus fruit and dried beans. Everyone needs regular folate because it’s important for healthy cell growth yet the body doesn’t store up enough of it.

And pregnant women need extra, even before they may know they’ve conceived. Enough folate in pregnancy’s earliest days can prevent devastating birth defects of the spine and brain called neural tube defects, including spina bifida. Those defects have dropped by about a third since the U.S. mandated fortifying certain breads, cereals and pastas with folic acid in January 1998.

Two major studies in the past month suggest the vitamin may be even more protective.

First, Texas researchers analyzed nearly 35,000 pregnancies and found that women who reported taking folic acid supplements for at least a year before becoming pregnant cut in half their risk of having a premature baby. Their risk of having very early preemies, the babies least likely to survive, dropped even more.

Then Canadian researchers analyzed 1.3 million births in Quebec since 1990 to look for heart defects, the most common type of birth defect. They found the rate of serious heart defects has dropped 6 percent a year since Canada began its own food fortification in December 1998.

It’s hard to get enough folate for pregnancy through an average diet. So health authorities have long advised that all women of childbearing age take a daily vitamin containing 400 micrograms of folic acid — even if they’re not trying to conceive, since half of pregnancies are unplanned. Last month, the U.S. Preventive Services Task Force went a little further, recommending that women take a daily supplement with 400 micrograms to 800 micrograms of folic acid daily.

But because only about a third of nonpregnant women take precautionary folic acid supplements, fortifying foods made with enriched flour ensures everyone gets a modest amount.

“We’ve seen in the U.S. and Canada dramatic changes in neural tube defects just with fortification. The question now is would a little more fortification, or even twice as much fortification, impact that bottom line, as well as those other potential benefits,” says Dr. Alan Fleischman, medical director of the March of Dimes.

His group will call together pregnancy and folate specialists this summer to debate that. Also under way are deliberations by the European Union and Britain on whether to begin fortification there.

Complicating that issue is the question about cancer risk when older people — women well beyond childbearing, and men — take lots of folic acid.

Here’s the quandary: Some research shows people who don’t eat enough folate have a higher risk of colon and certain other cancers. On the other hand, animal studies show too much folic acid, the pill version, can spur some cancers. There’s scant human evidence. But when researchers studied people prone to precancerous colon polyps, those who took high-dose folic acid — 1,000 micrograms a day — for three years had more new polyps than people given a dummy pill.