Methyl folate ((6S)-5-methyl tetrahydrofolate or 5-MTHF) is the most biologically active form of folic acid. Quatrefolic is the 4th generation development in folate delivery. With certain inherited errors in metabolism and under a variety of physiologic stresses, the transformation of folic acid into the active form of folate either does not properly take place or is inadequate. Unlike folic acid, this form of folate can cross the blood-brain barrier. Methyl folate is needed to support cardiovascular and neurologic health and proper cell division. folate supplementation during pregnancy has been shown to reduce the risk of neural tube birth defects.