This is a very interesting but rather long clip by Dr Ben Lynch about how bad folic acid is for the many people with a genetic mutation. My husband has the double MTHFR C677T one it turns out which can cause many diseases. I recommend you watch it as if you have this mutation it can have ramifications for your children and grandchildren too.
In about minute 59 near the end he mentions that both Keto and Paleo diets have little folic acid as they avoid most of the food which is fortified with folic acid. I wonder if the people benefiting from these diets have the methylation mutation? If so the short summary of this is throw away any supplements that contain folic acid or cyano cobalamin and make sure you are taking the methylated natural form of folate (L-methylfolate) and methyl and adenosyl cobalamin. Avoid any foods eg bread , cereal etc that are fortified as they will certainly be fortified with folic acid not the natural form.