Vitamin B12 deficiency and depletion has been identified as a wide-spread problem in populations with a low intake of animal source foods (Allen, 2012). Using IMMULITE, human milk vitamin B12 concentrations can now be compared across these populations. Since maternal B12 deficiency is known to result in neurological and developmental disorders in the exclusively breastfed infant, it is of critical importance to know what concentration of B12 in human milk is protective, whether
maternal supplementation during pregnancy and/or lactation is required, and if so, what level and timing of supplementation is appropriate.