Douglas Laboratories B-Complex is unique, including Metafolin, Methylcobalamin Vitamin B12, and Intrinsic Factor in its formulation. Metafolin contains only the S isomer of 5-MTHF and has been shown to be the only form of folate to be able to cross the blood-brain barrier.
https://www.amazon.com/Douglas-Laboratories%C2%AE-B-Complex-Metafolin-Supports/dp/B006U1220Y

