CHAPTER 2: MICRONUTRIENT UPDATE
As the life cycle turns, so the risk of micronutrient deficiencies changes. Causes and consequences of early childhood deficiencies have implications for later life and may be present as risk factors for future generations. Severe iron deficiency anaemia during pregnancy may even place a woman’s life at risk during childbirth. Starting with the foetus, iodine deficiency disorders (IDD) may cause brain damage or stillbirth. Folate deficiency of the pregnant woman may result in neural tube defects during foetal development. Iron deficiency anaemia and vitamin A deficiency in the pregnant woman may also have significant implications for the newborn infant, born with low stores. Vitamin A deficiency (VAD) may increase morbidity and mortality risk and affect vision, while anaemia and iodine deficiency disorders may lead to cognitive deficits. Other nutrients are important at certain times in life, such as calcium and folate in adolescence.
The Third Report described the situation of several micronutrient deficiencies in the developing world. While the focus then was primarily on iron, vitamin A, and iodine deficiencies, brief descriptions of the situation with regard to folic acid, zinc, and calcium were also included. A comprehensive review of the programmes to prevent and control these deficiencies was also provided.1 In this Fourth Report, we provide an update of progress in this area during 1998 and 1999, whether in improved knowledge of the nature, causes, or consequences of the problem or in the approaches adopted to deal with it.
We start by using the limited number of recent available surveys to present an update on the prevalence of anaemia as an indicator of iron deficiency and the magnitude of the population at risk of iodine deficiency. Using vitamin A as an example, we illustrate some of the difficulties in estimating the magnitude of the global problem for these three nutrients. While we recognize that other micronutrient deficiencies, such as zinc, are likely to be problems, we offer no estimates of their magnitude or severity as data simply do not exist. There remains a great need for nationally representative data on the prevalence and trends in these deficiencies to inform and improve policy and programme decisions. For each micronutrient, an update is also provided on strategies for the prevention and control of the deficiency. The final section considers the potential of multiple micronutrient supplementation and fortification and the advances being made to realize it.
Data in this chapter refer to stable populations. The micronutrient status of internally displaced people and refugee populations - including the sporadic outbreaks of more uncommon deficiencies such as scurvy, beriberi, and pellagra - is described in Chapter 5.
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