Metafolin is a new, coenzymated form of folic acid. Upon absorption into our bodies, folate is converted into L-methylfolate, the predominant form of folate in circulation and the only type that can cross the blood-brain barrier. This conversion is difficult for some people. As a result, they may not receive the full nutritional benefits of folic acid. Metafolin does not require enzymatic conversion. Preliminary research suggests that it is more bioavailable than folic acid.