Time for a Debate on Folate?
Too much of a good thing could turn out to be bad
Another worrisome finding comes from a recent cancer-prevention trial in which researchers gave pills containing 1,000 micrograms of folic acid to half of about 1,000 people. Over the next six years, both groups developed precancerous polyps at the same ratethough the people who'd been taking folic acid seemed more prone to particularly dangerous polyps. Moreover, they developed more unrelated cancersmostly prostate tumorsthan did people who received dummy pills.
Folate's effects on the brain, in contrast, appear to be mainly positive. For example, taking folic acid supplements seems to cut stroke risk by about 18 percent in people who are at elevated risk, according to a report in the Lancet in June. High folate levels also appear to preserve seniors' cognitive abilitiesusually. Two recent studies, however, suggested that they could have the opposite effect in seniors who have lower-than-average levels of vitamin B12. "These are just the first peeks at potential risks," says Martha Clare Morris, a nutritional epidemiologist at Rush University Medical Center in Chicago, who led one of the studies.
Right dosage. Even in this era of nationwide fortification, intake is largely under a person's control. Fortified foods add 128 micrograms of folic acid, on average, to a woman's daily intake, researchers at the Centers for Disease Control and Prevention recently found. A single daily multivitaminor a serving of heavily fortified breakfast cerealcan pack 400 micrograms, which by itself is enough to prevent the vast majority of neural tube defects. "I don't know what the cutoff would be, but you don't want to get toward 1,000 [micrograms per day]," says John Baron of Dartmouth, who coauthored the recent cancer-prevention study. One multivitamin "is probably neutral to beneficial. But don't take two." However, Xiaobin Wang of Children's Memorial Hospital in Chicago believes taking 400 to 800 micrograms of folic acid daily is often warranted for preventing stroke.
Toronto's Kim offers different counsel. While women of childbearing age should use multivitamins, he says, "I would definitely advise [other people] against taking supplements with folic acid." In particular, he says, that applies to anyone who has cancer or is at risk of harboring precancerous growths because of family history, genetics, or advanced age.
Nobody is calling for a change to the U.S. fortification policy at this point. Many women still aren't getting enough folate, notes Michael Katz, senior vice president for research at the March of Dimes. But some researchers urge other nations considering fortification, including Britain and Australia, not to adopt a policy just yet. And they're not ruling out a reversal here. Says Baron: "We're exposing a lot of people, and we're in the uncomfortable position of not really knowing what it does."
On the Plus Side
Although some studies hint at potential risks, folate is often beneficial.
Fetal health: Women who may conceive need folic acid to prevent birth defects. Get 600 micrograms daily during pregnancy; 1,000 is considered the upper limit.
Brain: Folic acid may reduce stroke risk and, in people with ample vitamin B12, may guard against cognitive impairment.
Cancer: Folate may ward off cancer in healthy people (but accelerate it in others, such as survivors harboring hidden malignancies).