Neufeld LM, Prentice AM (eds): Global Landscape of Nutrition Challenges in Infants and Children. Nestlé Nutr Inst Workshop Ser, vol 93, pp 1–13, (DOI: 10.1159/000503315) Nestlé Nutrition Institute, Switzerland/S. Karger AG., Basel, © 2020
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Global Landscape of Malnutrition in Infants and Young Children
Lynnette M. Neufelda · Ty Beala · Leila M. Larsonb · Françoise D. Cattaneoa
aGlobal Alliance for Improved Nutrition (GAIN), Geneva, Switzerland; bDepartment of Medicine, The University of Melbourne, Melbourne, VIC, Australia
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Abstract
Malnutrition during the first years of life has immediate adverse health consequences, including increased mortality risk, and impaired long-term health and capacities. Undernutrition is an important contributor to poor linear growth, stunting, which affects over 149 million children <5 years of age worldwide, one-third of whom live in India. Over 49 million children are wasted; yet globally, there are also 40 million overweight children. Up-to-date data on the magnitude and distribution of micronutrient malnutrition globally and in many countries are lacking. Anemia has been used as a proxy for micronutrient malnutrition; yet anemia, like stunting, has a complex etiology and numerous nonnutritional as well as nutritional causes. Undernutrition, specifically stunting, wasting, and micronutrient deficiency increasingly coexist with overweight, but accurate data to assess the extent to which these co-exist in countries, households, and individuals and the factors that predict it are scarce. Recent analyses in several countries suggest that there is substantial variability within and among regions in the prevalence and determinants of malnutrition. More and better data that can be used to tailor policies and programs to local contexts are urgently needed if we are to accelerate progress toward addressing malnutrition in all its forms.
© 2020 Nestlé Nutrition Institute, Switzerland/S. Karger AG, Basel
The Burden of Malnutrition in All Its Forms
The term malnutrition is often used synonymously with undernutrition. During childhood, undernutrition may result in inadequate linear growth (low height-for-age or stunting) or in insufficient accumulation of body mass (low weight-for-height or wasting) [1]. Micronutrient deficiency diagnosed through clinical symptoms or biomarkers of micronutrient status below established cutoffs is an additional form of undernutrition that affects children and adults alike. It is recognized, however, that overweight and obesity and the associated noncommunicable diseases are also forms of malnutrition affecting all age groups. Global goals now seek to address malnutrition in all its forms [2]. For example, the World Health Assembly has called for a 40% reduction in the number of children who are stunted, wasting no higher than 5%, and no increase in the number of overweight children by 2025 [3].
Malnutrition during the first years of life has immediate adverse health consequences and impairs long-term health and capacities. Children who become undernourished in early life are at a higher risk of dying, are more susceptible to illness, and may suffer growth and developmental delays [4]. Infections impair growth and nutrient absorption through a variety of mechanisms, such as reduced appetite, direct nutrient losses, and increased metabolic requirements or catabolic losses of nutrients through defecation, and may weaken transport of nutrients to tissues [5]. Children with adequate nutrition during early childhood have been shown to earn 21% more in wages as adults than children who were malnourished [6]. Overweight and obesity now contribute up to 7.1% of deaths [7], and there is a growing body of evidence that the risk of overweight and obesity starts in early life and increases during adolescence and adulthood [8].
UNICEF recently published updated statistics compiling data on nutritional status of children <5 years of age from all countries with available data [9]. From 2000 to 2018, the global prevalence of stunting in children <5 years of age decreased from 32.5 to 21.9% with prevalence decreasing across all regions globally. However, stunting still affected approximately 149 million children <5 years of age in 2018. At the same time, 49.5 million children (7.3%) were wasted, and an additional 40.1 million (5.9%) were overweight. South Asia has the highest prevalence of stunting (34.4%) and wasting (15.2%). While the actual number of children affected is lower in sub-Saharan Africa given population size, stunting prevalence remains very high (≥30%) across most countries. The number of children affected by stunting is decreasing across most regions, but there was a 29% increase in West and Central Africa, due to population growth. Overweight and obesity among children are increasing globally, but with substantial variability by region. For example, in Eastern Europe and Central Asia, overweight in children increased from 8.2% in 2000 to 14.9% in 2018. In the same period, the prevalence decreased in West and Central Africa from 4.2% in 2000 to 2.8% in 2018.
Unlike anthropometric measures of malnutrition, the global burden and trends in micronutrient deficiency in children are not well quantified. For years, the figure of 2 billion people affected by micronutrient deficiency has been quoted (see for example 10). Unfortunately, the empirical evidence that underpins this estimate is weak, likely based on anemia, iodine, and vitamin A deficiency prevalence from the early 1990 [11]. Thus, it is not useful for tracking progress. Given changes in dietary patterns [12], food fortification [13], and other interventions, its appropriateness even for advocacy purposes 20+ years on is questionable.
More recent data provide national, regional, and global estimates [14]. These have been incorporated in high-quality data visualization tools [10], but data limitations persist. First, the use of anemia as a proxy for micronutrient deficiency may not be appropriate in all regions given its complex etiology (discussed further below). Second, for some nutrients there are considerable limitations to existing biomarkers of status (e.g., blood or urine levels). In the case of zinc, for example, national food balance sheets have been used to estimate the proportion of the population with inadequate intakes as a proxy for deficiency [15]. There are several limitations to this approach including the very low quality of national food balance sheets to represent actual food intake of individuals [16]. Finally, infection and inflammation affect many biomarkers of nutritional status, and until recently, there has been little consensus on how to adjust prevalence estimates to account for this. For example, in one study in Indonesia, the prevalence of iron deficiency was substantially underestimated, while vitamin A and zinc prevalence were overestimated without adjustment for inflammation [17]. The recent Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia project has now published adjustment factors for several micronutrients that should help overcome this challenge [18].
Where high-quality recent