Intrinsic Factor

Without intrinsic factor, dietary B12 cannot be absorbed into the bloodstream regardless of how much is consumed. When the immune system attacks intrinsic factor or the stomach cells that produce it, the result is pernicious anemia. Intrinsic factor is a carrier transport protein secreted by the stomach lining that is required for B12 absorption. Intrinsic factor is a glycoprotein produced by the stomach lining that binds B12 and transports it to absorptive receptors in the small intestine. Stomach lining damage, such as from atrophic gastritis, can eliminate intrinsic factor production entirely, making high-dose oral B12 difficult to absorb through normal channels. A supplement called Cytoplan by Standard Process contains naturally sourced intrinsic factor combined with betaine HCl and is available without a prescription.