Harvard Heart Letter

Folic acid: Too much of a good thing?

As is true for many supplements, this vitamin may be a double-edged sword.

In 1996, the FDA ordered food makers to add folic acid to flour, breads, pasta, and other grain products. Babies were the reason "" folic acid helps prevent spina bifida and other birth defects. But there were also high hopes that adding this synthetic B vitamin would fight heart disease, some types of cancer, and age-related memory loss.

Folic acid fortification is working on the baby front. Fewer babies are born each year with spina bifida, partly because their mothers are getting extra folic acid from food and supplements. But the early enthusiasm that folic acid might prevent heart disease has been tempered by the results of clinical trials. And there's some evidence that too much folic acid may block the action of the natural form of the vitamin.

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