Lauran Neergaard

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 if 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.

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. And in March, researchers tracked 640 men from that earlier study and found that 10 years later, the folic acid users were more likely to have developed prostate cancer.

Why? While enough folate usually is protective, if people's bodies already harbor some precancerous or cancerous cells, too much may feed their growth, said Tufts' Mason. Older people are more likely to be brewing colon or prostate cancer.

Don't misunderstand: Everyone should eat enough leafy greens and citrus -- good folate from food is important at all ages. But until the issue's settled, Mason says older adults "really ought to think twice about whether you should take a vitamin supplement that contains folic acid."

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