CHAPTER 1: NUTRITION THROUGHOUT THE LIFE CYCLE
Nutrition challenges continue throughout the life cycle, as depicted in Figure 1.1. Poor nutrition often starts in utero and extends, particularly for girls and women, well into adolescent and adult life. It also spans generations. Undernutrition that occurs during childhood, adolescence, and pregnancy has an additive negative impact on the birthweight of infants. Low-birthweight (LBW) infants who have suffered intrauterine growth retardation (IUGR) as foetuses are born undernourished and are at a far higher risk of dying in the neonatal period or later infancy. If they survive, they are unlikely to significantly catch up on this lost growth later and are more likely to experience a variety of developmental deficits. A low-birthweight infant is thus more likely to be underweight or stunted in early life.
The consequences of being born undernourished extend into adulthood. Epidemiological evidence from both developing and industrialized countries now suggests a link between foetal undernutrition and increased risk of various adult chronic diseases - the “foetal origins of disease hypothesis.”1
Source: Prepared by Nina Seres for the ACC/SCN-appointed Commission on the Nutrition Challenges of the 21st Century.
During infancy and early childhood, frequent or prolonged infections and inadequate intakes of nutrients - particularly energy, protein, vitamin A, zinc, and iron - exacerbate the effects of foetal growth retardation. Most growth faltering, resulting in underweight and stunting, occurs within a relatively short period - from before birth until about two years of age.
Undernutrition in early childhood has serious consequences. Underweight children tend to have more severe illnesses, including diarrhoea and pneumonia. There is a strong exponential association between the severity of underweight and mortality.2 It has been estimated that out of 11.6 million deaths that occurred in 1995 among children under five in developing countries, 6.3 million (54%) were associated with low weight-for-age. The majority of these deaths can be attributed to the potentiating effect of mild to moderate undernutrition.3
The nutrition and health of school-age children in developing countries have only recently begun to receive attention. A long-standing assumption has been that by school age a child has survived the most critical period and is no longer vulnerable. However, many of the infectious diseases affecting preschool children persist into the school years. Until recently, data on the nutritional Status of school-age children were not routinely collected, despite growing evidence, first, that malnutrition was widespread in this age group, and second, that these nutritional problems adversely affect school attendance, performance, and learning.
In adolescence, a second period of rapid growth may serve as a window of opportunity for compensating for early childhood growth failure, although the potential for significant catch-up at this time is limited. Also, even if the adolescent catches up on some lost growth, the effects of early childhood undernutrition on cognitive development and behaviour may not be fully redressed.4 A stunted girl is thus most likely to become a stunted adolescent and later a stunted woman. Apart from direct effects on her health and productivity, adult stunting and underweight increase the chance that her children will be born with low birthweight. And so the cycle turns.
It is imperative to prevent foetal and early childhood undernutrition. Nutrition interventions in pregnancy and early childhood can result in improvements in body size and composition in adolescents and young adults. Improvements in both physical and intellectual performance were also found in a study by the Institute for Nutrition for Central America and Panama (INCAP).5
Investing in maternal and childhood nutrition will have both short - and long-term benefits of huge economic and social significance, including reduced health care costs throughout the life cycle, increased educability and intellectual capacity, and increased adult productivity. No economic analysis can fully capture the benefits of such sustained mental, physical, and social development.
The life cycle provides a strong framework for discussing the challenges facing human nutrition. Although information is available on preschool children in most regions, the paucity of data for other age groups precludes sub-regional and regional descriptions of the nutritional problems faced at these periods of the life cycle.
The causes of malnutrition are complex. Underlying the immediate causes of malnutrition will be a failure of either the main food, health, or care preconditions for good nutrition. The widely used food-health-care conceptual framework, shown in Appendix 1, offers an analytical tool for portraying causes of malnutrition and is used throughout this report.
For the most part, the results in this Fourth Report are presented according to the regions and sub-regions defined by the United Nations Population Division. A listing of the countries within each sub-region is provided in Appendix 2. These sub-regions are different from those used by the ACC/SCN since 1987. The objective of this change is to help standardize the use of common regions and sub-regions among UN agencies. WHO began to use this classification in 1993. Data described in this chapter derive from stable national populations. The nutritional status of refugees and internally displaced populations is described in Chapter 5.
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