Folic acid is the artificial form of B9, the natural form is folate and the active form, the form that is immediately used by the body is methylfolate.
The artificial form is everywhere, as the food industry has used it to fortify foods, in cheap supplements and ante natal formulas, it is unnatural and it has NO use to your body in this form, in short folic acid is toxic.
It has a negative impact on the expression of the MTHFR gene. The testing on this one gene SNP has exploded in recent years and it is the environmental impact on this gene that is causing so many problems. Miscarriages, birth defects and infertility to name a few. The trouble is we are bombarded by folic acid in foods, breads and cereals are all fortified with folic acid and in this form folic acid is harming us. We cannot process folic acid and unmetabolised folic acid causes imbalances in the body. It blocks the receptor site where natural folate needs to get into your cell. In this way folic acid blocks methylation.
If you have been given a vitamin pill with folic acid in it please dispose of it if you read supplements of foods with folic acid make other choices!
Dark green leafy vegetables are rich in the natural form of folate, methylfolate the form the body knows how to use which supports methylation pathways supports our innate detoxification.
WHY? Because plant based folate, active folate donates a methyl group that folic acid cannot.
In the rise of processed foods, longevity of foods, extending shelf life the outer nutritious part of the grain was milled out, steel ground flour no longer stone ground, the active folate removed and instead replaced by adding the toxic form folic acid, no methyl group, no use to the body.