Folic acid is one of the rare vitamin supplements with proven health benefits: Since it was added to enriched grain products in the 1990s, the risk of a certain kind of birth defect has plummeted. But recent studies suggest that too much can be dangerous. An excess may raise the risk of breast and colon cancers. Making matters worse, you can race past recommended levels just by taking a multivitamin and eating fortified breakfast cereal.
There’s no risk of overdosing on foods rich in folate (the natural form of this vitamin), such as leafy greens, beans, and orange juice. For now, though, people should avoid getting too much folic acid from fortified sources, says researcher Joel Mason, MD, of Tufts University.
“We’ve known for years that getting too little folate can promote cancer,” Dr. Mason says. “Now it looks like getting too much folic acid could be harmful too.”
If you eat one of these cereals and pop a multi, consider taking your supplement every other day, experts suggest. And pay attention to cereal serving size — it’s easy to pour a double.