Vitamin B12 is present in foods of animal origin, including dairy products and eggs. Thus, vegetarians are more susceptible to a dietary deficiency of this important nutrient.212 Likewise, vitamin B12 serum concentrations are reported to be significantly lower in elderly population groups compared to younger groups.213-216 It is estimated that 10% to 30% of individuals over the age of 50 have low stomach acid secretion217,218 which results in decreased bioavailability of vitamin B12 from food. To overcome food-bound vitamin B12 malabsorption problems, the Institute of Medicine recommends that vitamin B12-fortified foods (such as fortified ready-to-eat breakfast cereals) or supplements containing vitamin B12 be used to meet much of the requirement.219 Vitamin B12, or cobalamin, works synergistically with vitamin B6 and folate to regenerate (methylate) the amino acid methionine, which helps to maintain already healthy homocysteine levels already within normal range, which is important for heart health.220,221

Methylcobalamin is the form of vitamin B12 active in the central nervous system. It is an active coenzyme of the vitamin B12 analogs that are essential for cell growth and replication. The liver may not convert cyanocobalamin, the common supplemental form of vitamin B12, into adequate amounts of methylcobalamin that the body may need for proper neuronal functioning.222,223 Methylcobalamin may exert its neuroprotective effects through enhanced methylation, acceleration of nerve cell growth, or its ability to promote already healthy homocysteine levels within normal range.221-223