Read this article. I have both the MTHFR and COMT genetic defects which might be related to my B12 absorption genetic defect. It's contradictory how you're not supposed to take a particular vitamin for MTHFR if you have COMT and vice versa. Maybe I could message the author of this article. This Niacin in the B Complex is killing me making me feel so wired. Plus, I can't take the same vitamin for both MTHFR and COMT genetic defects.