This study may interest NT members who take folate supplements because they know or suspect that they have mutations in one or both copies of their MTHFR genes High folic acid consumption leads to pseudo-MTHFR deficiency, altered lipid metabolism, and liver injury in mice. - PubMed - NCBI.

While it is an animal model it suggests that high folate intake can have adverse health outcomes.

The RDA for folate is about 400 ug/day for both men and women and the Tolerable Upper Intake Level is 1 mg/day Dietary Supplement Fact Sheet: Folate — Health Professional Fact Sheet.