5-MTHF is a high quality essential B vitamin. Acting with vitamin B12, 5-MTHF functions as a methyl-group donor. Many individuals don't get sufficient 5-MTHF (L-5-Methyltetrahydrofolate) which is the active form of folic acid. A deficiency of folic acid has been linked to low-birth-weight infants and neural tube defects, which is why the Centers for Disease Control recommends folic acid supplementation for all women of childbearing age.Thorne's logo, text, trademarks, graphics, videos and photo images are the property of Thorne and are used with permission. Copyright © 2023*FDA Disclaimer: The information about this product and statements made are provided by the manufacturer, except customer reviews which are not evaluated. See www.thorne.com for information about the relationship between this product and any claims made. Results may vary from person to person based on body size and other factors, and the effectiveness is not guaranteed for you. Always seek the advice of your healthcare professional about taking dietary, nutritional, herbal or homeopathic supplements.