chapter 2. 2 r e

Child stunting in hapt C developing countries

Stunting and in children the most effective intervention is the there are others such as head cir- are measures reflecting states of supply of foods with adequate nutri- cumference and mid-upper arm chronic and acute undernutrition tional quality to complement breast- circumference that are commonly that have important adverse effects feeding in the first 2 years of life. used in surveillance for severe on survival, health, and develop- The physical growth of children acute . ment. In impoverished settings, within a normative range has im- Length (recumbent, for age poor-quality diets and high rates of portant implications both within < 2 years) or height (standing, for infection, both in pregnancy and in that age span and into adulthood age 2–4 years) or weight is com- the first 2 years of life, lead to fe- (Bhutta et al., 2013). Insufficient pared to an international growth tal growth restriction (FGR) and gains in length/height and weight standard (WHO Multicentre Growth poor growth. This results in from birth to age 5 years, resulting Reference Study Group, 2006), an estimated 26% of the world’s from childhood undernutrition, put and the result is most commonly children younger than 5 years hav- the child at increased risk of mor- expressed as a Z-score (standard ing stunted stature, and 8% be- bidity and mortality from infectious deviation score). The Z-score is the ing much too thin for their height diseases as well as impaired mental observed value for length/height or (i.e. wasted) (UNICEF-WHO-The development, reduced learning ca- weight minus the median value of World Bank, 2012). Proven inter- pacity in school, and lower earning the growth standard, with this result ventions to prevent the FGR that potential as an adult, among other divided by the standard deviation of contributes to stunting include mul- effects (Victora et al., 2008; Adair the growth standard. If the Z-score tiple vitamin and mineral supple- et al., 2013; Bhutta et al., 2013). for length/height-for-age is below ments and provision of balanced As noted, childhood undernutri- −2, the child is considered to have energy/protein supplements to tion is usually defined by physical inadequate linear growth or to be pregnant women, as well as control size. Measures of length/height and stunted. If the Z-score for weight- of maternal infections. After birth, weight are most common, although for-age is below −2, the child is said

Chapter 2. Child stunting in developing countries 7 to be . The weight and 1990, with an average annual rate to infectious agents and toxins. The length/height measures can be used of reduction of 2.1%. The preva- global prevalence of moderate or together to create an indicator of lence of stunting varies substan- severe wasting was estimated to be wasting: a child whose Z-score for tially by world region (Fig. 2.1), with 8.0% (95% CI, 6.8–9.3%) for 2011. weight-for-length/height is below −2 the highest prevalence in Africa and Again, there is regional variation in is considered to be wasted. South-Central Asia (which includes the prevalence (Fig. 2.3), with the India). The decline in the preva- highest prevalence in South-Central Prevalence of child lence of stunting has been greater Asia (14.8%; 95% CI, 11.1–19.4%), malnutrition for Asia and Latin America than South-East Asia (9.7%; 95% CI, for Africa, which is the only region 7.5–12.6%), and Africa (8.5%; 95% The latest UNICEF-WHO-The World that has had an increasing number CI, 7.4–9.6%). The numbers of chil- Bank joint child malnutrition esti- of stunted children, due to the slow dren with wasting and severe wast- mates provide global and regional declines in the prevalence and the ing were estimated to be 52 million prevalences for stunting and wast- high fertility rate (Fig. 2.2) (UNI- and 19 million, respectively, for ing based primarily on population- CEF-WHO-The World Bank, 2012; 2011. Recent estimates indicate that based, nationally representative Bhutta et al., 2013). nearly 2 million deaths in children surveys, with modelling to make In countries with an overall preva- worldwide can be attributed to FGR regional estimates (UNICEF-WHO- lence of stunting greater than 10%, and stunting, or a third of all child The World Bank, 2012). The global there is a gap – in some cases very deaths (UNICEF-WHO-The World prevalence of stunting in children wide – between the high prevalence Bank, 2012; Bhutta et al., 2013). younger than 5 years was estimated in the poorest 20% and the low prev- to be 26% (95% confidence interval alence in the least poor 20% of the Risk factors for child [CI], 24–28%) for 2011, the most re- population. This illustrates the rela- malnutrition cent data. The number of stunted tionship of stunting and other forms children in that year was estimated of undernutrition with poverty and Preventable causes of FGR in utero to be 165 million. The prevalence of the associated problems of food in- and reduced growth of the child dur- stunting has declined from 40% in security and environmental exposure ing the first 2 years of life include low

Fig. 2.1. Latest country prevalence estimates for stunting among children younger than 5 years. Source: Reprinted from UNICEF-WHO-The World Bank (2012), p. 9, © 2012, with the permission of the publisher.

8 Fig. 2.2. Trends in prevalence and numbers of children with stunted growth (height-for-age Z-score < −2), by selected United Nations regions and globally, 1990–2010, and projected to 2025 on the basis of United Nations prevalence estimates. Source: Reprinted from Black et al. (2013), © 2013, with permission from Elsevier. Data from UNICEF-WHO-The World Bank (2012). 2 r e hapt C

Fig. 2.3. Latest country prevalence estimates for wasting among children younger than 5 years. Source: Reprinted from UNICEF-WHO-The World Bank (2012), p. 10, © 2012, with the permission of the publisher.

Chapter 2. Child stunting in developing countries 9 , small weight gain High rates of diarrhoea and other and quality of diets and provision and micronutrient deficiencies dur- infectious diseases also affect this of safe food supplements contain- ing pregnancy, and maternal infec- age group, even with continued ing adequate micronutrients have tions (Bhutta et al., 2013; Christian et as complementary been shown to improve growth and al., 2013). It has been estimated that foods are introduced. In a pooled reduce the prevalence of stunting. 27% of all births in low- and middle- analysis of nine community-based Full (90% coverage) implementa- income countries have FGR, with the studies in low-income countries, the tion of these interventions would re- highest prevalence in Asia, especial- odds of stunting at age 24 months duce stunting by at least 20% in the ly South Asia (Bhutta et al., 2013; Lee increased multiplicatively with each 34 countries that include 90% of the et al., 2013). Nutritional status at birth episode of diarrhoea or day of di- world’s stunted children (Fig. 2.4). is related to the risk of being stunted arrhoea before that age. The pro- These interventions would also be at age 2 years. Globally, it has been portion of stunting attributed to five useful to prevent wasting (Bhutta et estimated that 20% of stunting can previous episodes of diarrhoea was al., 2013). In stable non-emergency be attributed to FGR. In some coun- 25% (95% CI, 8–38%) (Checkley et situations, wasting usually coexists tries the attributable fraction is even al., 2008). In addition to the clinical with stunting after age 6–9 months. higher. In India, where nearly half of infections, frequent exposure to con- However, severe acute malnutrition all births have FGR, the attributable taminated food and water and the (i.e. severe wasting) can occur more fraction for stunting is more than a household environment results in abruptly even in a previously well- third (Christian et al., 2013). ingestion of microbes, causing sub- nourished child due to food scarcity, Most of the growth faltering lead- clinical infections that damage the such as in famine, natural disaster, ing to stunting occurs between small intestine. It has been hypoth- or civil conflict. These are situations ages 3 months and 18–24 months esized that environmental enteric where targeted food distribution pro- (Victora et al., 2010), a period of vul- dysfunction (EED) or environmental grammes are needed. nerability because often insufficient enteropathy, a condition character- There is limited evidence that and poor-quality food is provided to ized by structural abnormalities of interventions in sectors other than the child. Exclusive breastfeeding is the intestinal epithelium, altered bar- health and may have a recommended for the first 6 months rier integrity, mucosal inflammation, beneficial impact on stunting. These of life but is uncommonly practiced; and reduced nutrient absorption, areas include efforts to improve ag- globally, only about 30% of may contribute to growth faltering ricultural productivity and improve- aged 1–5 months are exclusively and stunting (Keusch et al., 2013). It ments in water, , and hy- breastfed (Bhutta et al., 2013). The has also been hypothesized that zinc giene, because of their potential to early introduction of fluids will re- deficiency may be involved in the reduce the rates of diarrhoea and duce the production and ingestion pathogenesis of EED (Lindenmayer possibly the occurrence of EED of breast milk and substitute foods et al., 2014). As noted by Lunn (Dangour et al., 2013; Spears, 2013). of lesser nutritional quality that also (2000) and discussed later in this Food safety interventions would be have a high risk of microbial con- Report, there is a potential role for expected to positively influence nu- tamination. In most of the affected ingested mycotoxins to contribute trition and growth in young children regions, more than 60% of children to EED or to other mechanisms that by eliminating infectious agents that aged 6–23 months are breast- lead to stunting. cause diarrhoea through foodborne fed (Bhutta et al., 2013). However, transmission and possibly through the complementary foods that are Interventions against child avoidance of exposure to chemicals introduced too often have inad- malnutrition and mycotoxins. equate nutrient density, calories, protein, essential fats, and micronu- Although breastfeeding, as recom- Key scientific gaps and trients, and may contain infectious mended for the first 2 years of life, is research needs bacteria and/or toxins. Deficiency important for the babies’ health and of the micronutrient zinc has been dietary intake, the major interven- Recent publications indicate that consistently associated with stunt- tions to prevent stunting are related FGR is a more important contribu- ing, and increased linear growth in to the foods that are given in addition tor to neonatal and mortality infants has been demonstrated with to breast milk from age 6–23 months (Katz et al., 2013) and to stunted provision of daily zinc supplements (i.e. complementary diet). Educa- linear growth (Christian et al., (Bhutta et al., 2013). tion about age-appropriate quantity 2013) than previously recognized.

10 Fig. 2.4. Countries with the highest burden of malnutrition. These 34 countries account for 90% of the global burden of malnutrition. Source: Reprinted from Bhutta et al. (2013), © 2013, with permission from Elsevier. 2 r e hapt C

This makes it imperative to look with multiple micronutrients in preg- ments improves growth and reduces more closely at the causes of FGR nancy, instead of only iron and the occurrence of stunting; however, and possible interventions to re- folic acid, would provide added the effect size relative to the height duce it or ameliorate its negative benefits at modest additional cost. deficit is small. Zinc supplements effects. Maternal undernutrition and If multiple micronutrients are to be for children in the first 2 years of infection, as well as other possible provided to pregnant women or to life also have a statistically signifi- determinants of FGR, need addi- children, further product develop- cant, but small, benefit in reducing tional study, especially to identify ment research, linked with stud- stunting. nutrition series feasible interventions to reduce its ies of the prevalence and extent of estimated that the nutrition-specific occurrence. If programmes intend micronutrient deficiencies in various interventions together, if scaled up to increase the provision of bal- low-income populations, is needed. to 90%, would reduce the preva- anced energy/protein supplements This will ensure that the composi- lence of stunting by only about 20% during pregnancy, there are ques- tion is optimized to meet nutritional (Bhutta et al., 2013), illustrating the tions about the composition of sup- needs, reduce nutrient interactions, large gap in our knowledge of how plements (preferably using locally avoid side-effects, enhance accept- to prevent stunting. Additional stud- available and safe foods) and their ability, and reduce costs. ies of the determinants of stunted timing in pregnancy, how best to Most stunting of linear growth growth need to include the possible target the food supplements to vul- takes place in the first 2 years of role of subclinical infections and ex- nerable populations and undernour- life. The relative contributions to posure to potentially harmful agents ished or food-insecure women, how stunting of dietary insufficiency, such as mycotoxins. to achieve sufficient consumption, infectious diseases or subclinical The first 2 years of life are a and ultimately the cost–effective- infections, and inflammation are un- crucial period for both develop- ness of alternative ways to deliver known and may vary, as does the ment and growth, which need to this intervention. prevalence of stunting, by setting in be considered separately as well In spite of the known benefits of low- and middle-income countries. as jointly. Young children in impov- iron and folic acid supplementation There is good evidence that promo- erished households lack both the in pregnancy, the current use of this tion of nutritious complementary stimulation needed for cognitive and intervention is low. Supplementation foods or provision of food supple- psychosocial development and the

Chapter 2. Child stunting in developing countries 11 food and environmental conditions serious consequences for survival, derstanding of the behavioural and needed to promote physical growth health, and development. Implemen- biological determinants of stunting and prevent illness. tation of proven interventions to pre- and wasting, including the possible In conclusion, stunting and wast- vent their occurrence and to provide role of mycotoxins, and the effec- ing are nutritional conditions that most treatment must be given greater pri- tiveness of other nutrition-specific commonly affect children in low- and ority. Parallel efforts should address interventions and nutrition-sensitive middle-income countries and have the evidence gaps through better un- approaches.

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