evidence: The MTHFR gene has been the subject of health misinformation before, particularly in relation to vaccines due to misinterpretation of a scientific study, as we reported in a previous Health Feedback review. It’s also not the first time it was cited in a claim related to folic acid. As we will explain below, the claims made in the Brad Lea video are inaccurate and misleading. [...] The claim that "the MTHFR gene mutation" prevents the body from processing folic acid properly is misleading. MTHFR is a gene that codes for the enzyme methylenetetrahydrofolate reductase. Enzymes are proteins that facilitate chemical reactions. Methylenetetrahydrofolate reductase is involved in processing folate, including folic acid, to produce proteins and other compounds. [...] In fact, there are more people in the U.S. who have MTHFR gene variants than those who don’t. The most common variant is C677T. In the U.S., about 25% of people who are Hispanic, and 10 to 15% of people who are Caucasian have two copies of C677T. The CDC clarified that people with the C677T variant "can safely and effectively process all different types of folate, including folic acid". There’s also no evidence that unmetabolized folic acid in the blood is harmful. Folic acid is water-soluble, therefore excess folic acid doesn’t build up in the body as it is excreted into the urine.