Vitamin B12 is the only natural product that contains cobalt, to which it owes its bright red color. In humans, it is difficult to observe a pure form of B12 avitaminosis, while it is usually accompanied by a lack of folic acid and the endogenous factor produced by the acidifying cells of the stomach and in its deficiency (achlorhydria), malabsorption of vitamin B12 occurs. After being absorbed with the help of the endogenous factor, B12 acts as a coenzyme in folic acid for the synthesis of DNA, participates in the synthesis of nerve myelin and has an anti-atherosclerotic effect. Vitamin B12 is found in foods of animal origin, such as meat, and for this reason, doctors usually recommend that vegetarians take vitamin B12 supplements.