5-MTHF, also known as Methylfolate, is the preferred form of folate supplementation because it is the active form of folate used by the body’s tissues.

Many individuals don't get sufficient 5-MTHF (L-5-Methyltetrahydrofolate), the active form of folic acid, because they have intestinal or liver dysfunction, or because they are among the three out of five Americans whose genetic makeup makes it difficult to convert folic acid into active 5-MTHF. 

Benefits of Thorne’s 5-MTHF: 

• An adequate amount of 5-MTHF is essential for the production of the neurotransmitters serotonin, melatonin, dopamine, and epinephrine – all of which support healthy brain function and mood.
• Acting with vitamin B12, 5-MTHF functions as a methyl-group donor, thereby facilitating healthy methylation and homocysteine levels.
• Folic acid is especially important before conception and during early pregnancy, because its biggest need is during the first trimester – when a woman might not know she is pregnant. A folic acid deficiency is linked to low-birth-weight infants and neural tube birth defects

5-methyltetrahydrofolate (5-MTHF) supplementation is not recommended concurrent with methotrexate cancer therapy, as it can interfere with methotrexate's anti-neoplastic activity; however, this folate source has not been shown to interfere with the anti-inflammatory activity of methotrexate. An individual taking methotrexate for psoriasis or rheumatoid arthritis can safely take a supplement containing folate.