The natural folate found in leafy greens, orange juice and other foods is perfectly healthy, but recent studies found that the folic acid supplement levels found in cereals, breads and breakfast bars may be causing lung and prostate cancers to grow.  If you take a multivitamin and eat lots of cereal, rice and bread, you may be getting way more than the 400 mcg recommended.  Switch to whole grain products that aren’t fortified, read labels, and remember that your multi alone has the RDA.  Vitamin A, vitamin E and iron are three more to consume with caution.