In Praise of Folic Acid

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Should everyone be getting more folic acid? That's the question on a lot of doctors' minds this week. Though not as famous as vitamin C, folic acid plays a crucial role in the development of just about every cell in the body. A member of the B-vitamin family, it's found naturally in orange juice, beans and green vegetables. There is some evidence that folic acid may reduce the risk of heart disease, but it is best known for its role in preventing spina bifida and other birth defects. Indeed ever since 1998, when the Food and Drug Administration mandated that it be added to cereal products, the number of so-called neural-tube defects has dropped nearly 20% in the U.S.

Now comes word that the vitamin may, just may, help ward off the ravages of Alzheimer's disease. In a study of more than 1,000 older adults published in the New England Journal of Medicine, researchers at Boston University and Tufts University found that subjects who had high levels of a particular amino acid called homocysteine in their blood were twice as likely to develop Alzheimer's as those who didn't. The finding is important because one of the easiest ways to lower homocysteine levels is to get plenty of folic acid.

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The study, although not definitive, is the strongest evidence to date that homocysteine plays a role in Alzheimer's. Previous research had found that Alzheimer's patients often have high levels of the amino acid in their blood--though that could be because folks with Alzheimer's often don't eat very well.

The new study lays that explanation to rest. As part of the famous Framingham study, which has tracked the development of heart disease among residents of Framingham, Mass., for more than 50 years, researchers in the 1970s started measuring the homocysteine levels of men and women who had not yet developed dementia. Those patients whose homocysteine levels measured over 14 micromoles a liter while they were still healthy were twice as likely to be diagnosed with Alzheimer's disease later on.

That doesn't mean that if you have high homocysteine levels, you will get Alzheimer's, or that low homocysteine levels will protect you from dementia. It's not even certain, warns Dr. Sudha Seshadri, a neurologist at Boston University who led the study, that "lowering homocysteine levels will lower the risk of Alzheimer's." But the case for adding folic acid to your diet is getting better all the time.

Of course the best source of any vitamin is a healthy diet. For those of us who still don't eat our beans and vegetables, most multivitamins contain the recommended daily folic-acid dose of 400 micrograms. (Eating four slices of enriched bread gives you the equivalent of roughly 100 micrograms.) There is no risk of overdose, although high levels of folic acid can mask the signs of pernicious anemia in people who have developed the disorder. Folic acid by itself may not keep the doctor away, but there's no harm trying.

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