Conclusions of a WHO Technical Consultation on folate and vitamin B12 deficiencies

Abstract

Folate and vitamin B12 deficiencies occur primarily as a result of insufficient dietary intake or, especially in the case of vitamin B12 deficiency in the elderly, poor absorption. Folate is present in high concentrations in legumes, leafy green vegetables, and some fruits, so lower intakes can be expected where the staple diet consists of unfortified wheat, maize, or rice, and when the intake of legumes and folate-rich vegetables and fruits is low. This situation can occur in both wealthy and poorer countries. Animal-source foods are the only natural source of vitamin B12, so deficiency is prevalent when intake of these foods is low due to their high cost, lack of availability, or cultural or religious beliefs. Deficiency is certainly more prevalent in strict vegetarians, but lacto-ovo vegetarians are also at higher risk for inadequate intakes. If the mother is folate-depleted during lactation, breastmilk concentrations of the vitamin are maintained while the mother becomes more depleted. In contrast, vitamin B12 concentrations in breastmilk can be markedly lower in vitamin B12-depleted women. The impact of gene polymorphisms on folate and vitamin B12 status and requirements in a population will vary depending on the underlying prevalence in that population. Although not well understood, gene polymorphisms almost certainly affect the risk of adverse pregnancy outcomes. Folic acid and vitamin B12 in synthetic form are absorbed at about twice the efficiency as the food forms, especially in lower doses. © 2008, The United Nations University.