Actually, DHFR enzyme plays an important role during folate metabolism.  

The function of DHFR is to decompose natural folate and synthetic folic acid into active folate (5-MTHF) .

DHFR acts quickly on natural folate, but slowly on folic acid. It can only metabolize about 266 mcg folic acid per day.

Taking folic acid more than 266mcg, the Unmetabolized folic acid(UMFA) will build up in our body.

UMFA may inhibit DHFR and reduce our ability to metabolize natural folate through diet and disrupt our normal folate metabolism. This will lead to a sharp decrease of bioactive folate in our body and other physiological side effects.

Magnafolate® ,the Manufacturers & Supplier of active folate.