Enhanced B Complex provides the most biologically active forms and clinically relevant doses of a unique B vitamin combination. Quatrefolic folate provides (6S)-5-Methyltetrahydrofolate acid (MTHF), the active form of folate at the cellular level, the form found in circulation, and the only form able to cross the blood brain barrier. This form of folate bypasses enzymatic conversion by methylene tetrahydrofolate reductase (MTHFR), an enzyme with common genetic polymorphisms known to impair activity. Quatrefolic acid administration has been associated with higher peak (6S)-5-MTHF levels than both folic acid and calcium 5-MTHF, with higher plasma folate levels even in those with high functioning MTHFR polymorphisms