Metafolin®, a breakthrough development in folate supplementation discovered by Merck Eprova Ltd, a subsidiary of Merck KGaA, has been introduced by Source Naturals, Scotts Valley, CA. All absorbed food folates and folic acid supplements must go through methylation in the liver and intestines where they are converted to L-methylfolate. This is the common form of folate that circulates in the blood for use by cells. Metafolin is delivered in the L-methyfolate stage and requires no conversion.