Vitamin B12 is available in several supplemental forms, of which cyanocobalamin & hydroxycobalamin are the main synthetic forms that have a cyanide molecule attached, while adenosylcobalamin and methylcobalamin occur as two coenzymatically active and more efficient forms. In animal experiments, both of these active forms have demonstrated to reduce tumor growth, with methylcobalamin being superior in promoting nerve regeneration as well. However, other research has not only suggested an increase in cancer or tumor cell divisions from receiving higher doses of Vitamin B12, but also the presence of higher Vitamin B12 levels with some heart and liver conditions, and acute or chronic myelogenous leukemia... Full Text