Objective: To provide current global and regional estimates of anaemia prevalence and number of persons affected in the total population and by population subgroup. Setting and design: We used anaemia prevalence data from the WHO Vitamin and Mineral Nutrition Information System for 1993-2005 to generate anaemia prevalence estimates for countries with data representative at the national level or at the first administrative level that is below the national level. For countries without eligible data, we employed regression-based estimates, which used the UN Human Development Index (HDI) and other health indicators. We combined country estimates, weighted by their population, to estimate anaemia prevalence at the global level, by UN Regions and by category of human development. Conclusion: Anaemia affects one-quarter of the world's population and is concentrated in preschool-aged children and women, making it a global public health problem. Data on relative contributions of causal factors are lacking, however, which makes it difficult to effectively address the problem.
Folate and vitamin B 12 deficiencies occur primarily as a result of insufficient dietary intake or, especially in the case of vitamin B 12 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 B 12 , 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 B 12 concentrations in breastmilk can be markedly lower in vitamin B 12depleted women. The impact of gene polymorphisms on folate and vitamin B 12 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 B 12 in synthetic form are absorbed at about twice the efficiency as the food forms, especially in lower doses.
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