This vitamin has been isolated as the “ant-pernicious anemia” factor. That is, it is essential for the production and development of red blood cells; without vitamin B12, anemia will eventually develop. All of the vitamin B12 available to man originally come from bacteria or fungi. Intestinal bacteria in man is a significant contributor in this respect. Vitamin B12 deficiency is seen chiefly among vegetarians and where special absorptive problems exist.
The requirement for vitamin B12 during pregnancy has been set at 2.6 microgram. In some cases, a dietary supplement or periodic intramuscular injection of vitamin B12 is indicated. Insufficient vitamin B12, an inherent problem in strict vegetarian diet, during pregnancy and breastfeeding, has been reported to result in some cases, in failure to thrive and developmental delay in infants and young children.
