Vitamin B9 / folate / folic acid / methylfolate

Also known as 5-MTHF, l-methylfolate, folacin, folic acid, folate.

Last reviewed October 9, 2026 · Jump to references

What is Vitamin B9 / folate / folic acid / methylfolate?

In plain words

Vitamin B9 is a nutrient found naturally in foods as folate and added to fortified foods and supplements as folic acid or methylfolate. The body processes these forms to help make DNA and healthy blood cells. Researchers study folate in pregnancy, heart health and brain function; folic acid has strong evidence for preventing certain brain and spine birth defects. High folic acid intake can hide the anemia caused by vitamin B12 deficiency while nerve damage continues.

Technical definition

Vitamin B9 comprises water-soluble folate compounds with a pteridine–para-aminobenzoate–glutamate structure; folic acid is a synthetic oxidized form, while L-methylfolate (5-MTHF) is a major circulating reduced form. Folates act as enzyme cofactors rather than receptor ligands: folic acid undergoes reduction before entering folate metabolism, and 5-MTHF supports vitamin B12-dependent methionine synthase in converting homocysteine to methionine, linking folate to DNA synthesis and methylation. Folate forms are available in foods, fortified foods and dietary supplements, with regulatory classification varying by product and jurisdiction.

Educational information only. This page does not provide medical advice or determine whether a supplement is appropriate for you. Review supplements with a qualified healthcare professional, especially if you take medication, are pregnant, have surgery scheduled, or have a chronic medical condition.

Evidence by use

Each use is rated on its own. There is no single overall effectiveness score.