In general, a Tolerable Upper Intake Level (UL) is the maximum daily dose unlikely to cause side effects. Synthetic folic acid from fortified food or supplements (excluding folate from food) is set at 1,000 mcg daily for adults. Above that, folic acid has been linked to increased cancer growth and other negative effects.  No safe upper limit has been set for naturally occurring folate from foods such as dark leafy greens, beans, or asparagus, but naturally occurring folate is unlikely to contribute to the same side effects as those of folic acid.