ABSTRACT
This chapter presents the intake and status of vitamin B12 in the general population as well as in athletic populations. Cobalamins are critical for cell growth and division, by acting as coenzymes in two reactions, methylcobalamin in methionine synthase and adenosylcobalamin in methyl malonyl CoA mutase. Vitamin B<Sub>12</Sub> status can be assessed by biochemical measurements and by clinical indications, such as the presence of macrocytic anemia increased mean cell volume and decreased hemoglobin levels. The recommended dietary allowance is the term used to describe the amount of intake of a necessary nutrient considered to be sufficient to meet the needs of most healthy persons, what is needed to prevent a deficiency. Vitamin B12, as a necessary cofactor for methionine synthetase, acts to help control the total plasma level of homocysteine. Increased levels of homocysteine could result from a decrease in vitamin B<Sub>12</Sub> levels or a dysfunction in B<Sub>12</Sub> metabolism.
