Several contributory factors such as poverty, lack of purchasing power, household food insecurity, and limited general knowledge about appropriate nutritional practices increase the risk of undernutrition in developing countries. The synergistic interaction between inadequate dietary intake and disease burden leads to a vicious cycle that accounts for much of the high morbidity and mortality in these countries. Three groups of underlying factors contribute to inadequate dietary intake and infectious disease: inadequate maternal and child care, household food insecurity, and poor health services in an unhealthy environment.
Nutritional deficiencies are widely prevalent globally, and contribute significantly to high rates of morbidity and mortality among infants, children, and mothers in developing countries. Several contributory factors such as poverty, lack of purchasing power, household food insecurity, and limited general knowledge about appropriate nutritional practices increase the risk of undernutrition in developing countries. The most recent estimates indicate that 178 million children younger than 5 years are stunted, representing 32% of all children worldwide, and a further 19 million have severe acute malnutrition (SAM).
To understand better what causes undernutrition, it is necessary to systematically evaluate the causes and determinants of undernutrition at different levels. Fig. 1 illustrates a well-recognized conceptual framework across the life span, indicating how nutrition problems may have an impact across various age groups and could potentially lead to intergenerational effects. The widely used conceptual framework of proximal and distal determinants developed by UNICEF ( Fig. 2 ) also illustrates these causes, and their interactions. The synergistic interaction between the 2 causes (inadequate dietary intake and disease burden) leads to a vicious cycle that accounts for much of the high morbidity and mortality in developing countries. Three groups of underlying factors contribute to inadequate dietary intake and infectious disease: inadequate maternal and child care, household food insecurity, and poor health services in an unhealthy environment.
Epidemiology and burden of undernutrition
Undernutrition magnifies the effect of every disease, and children are the most visible victims of nutritional deficiencies. Poor nutrition contributes to 35% of the 9.2 million child deaths each year globally. Asia, Africa, and Latin America are major contributors to the burden of disease attributable to maternal and child undernutrition, as only 1% of deaths in children younger than 5 years occurs outside these regions. The estimated proportions of deaths in which undernutrition is an underlying cause are roughly similar for diarrhea (61%), malaria (57%), pneumonia (52%), and measles (45%). Micronutrient deficiencies are now recognized as important contributors to the global burden of disease, especially in developing world.
One commonly used effectiveness measure for health interventions is the disability-adjusted life year (DALY). DALYs combine years of life lost due to premature death and years of life lived with disabilities (YLD) into one indicator, allowing assessment of the total loss of health from different causes. One DALY can be regarded as roughly 1 lost year of so-called healthy life. Nutrition interventions (as general, preventive, public health measures) have an extensive estimated benefit in terms of reducing the burden of disease, as measured by DALYs. Table 1 summarizes the estimated DALYs due to undernutrition and micronutrient deficiencies.
| Deaths | % of Deaths in Children Younger than 5 | Disease Burden (1000 DALYs) | % of DALYs in Children Younger than 5 | |
|---|---|---|---|---|
| Underweight | 1957530 | 19.0 | 81358 | 18.7 |
| Stunting | 1491188 | 14.5 | 54912 | 12.6 |
| Wasting | 1505236 | 14.6 | 64566 | 14.8 |
| Intrauterine growth retardation | 337047 | 3.3 | 13536 | 3.1 |
| Vitamin A deficiency | 667771 | 6.5 | 22668 | 5.3 |
| Zinc deficiency | 453207 | 4.4 | 16342 | 3.8 |
| Iron deficiency | 20854 | 0.2 | 2156 | 0.5 |
| Iodine deficiency | 3619 | 0.03 | 2614 | 0.6 |
According to a recent review in the Lancet, undernutrition was responsible for the largest disease burden, whereas burden with wasting is slightly less than that of stunting. Within developing countries, South Central Asia has the highest disease burden due to stunting and wasting, with India alone having 600,000 deaths annually. Undernutrition is high in Eastern, Middle, and Western Africa, with an estimated 111 million deaths in children younger than 5 years in the region. Among vitamins and minerals, vitamin A and zinc deficiencies have the largest disease burden globally, with 6% and 5% of under-5 deaths, respectively, the highest burden being in South Central Asia. On the other hand,iodine and iron deficiency contribute to a relatively small burden of disease ( Table 2 ).
| Micronutrient Deficiency | Burden of Disease |
|---|---|
| Vitamin A deficiency | Nearly 800,000 deaths among women and children worldwide can be attributed to vitamin A deficiency (VAD). 20% of maternal deaths worldwide can be attributed to VAD. South East Asia and Africa have the highest burden of VAD |
| Iron deficiency and anemia | Iron deficiency contributes to 18.4% of total maternal deaths and 23.5% of perinatal deaths 115,000 maternal deaths and 591,000 perinatal deaths globally can be attributed to iron deficiency. 814,000 deaths globally can be attributed to iron deficiency anemia |
| Zinc deficiency | The estimated global prevalence of zinc deficiency is 31%. Zinc deficiency contributes to increased risk of childhood diseases, a main cause of death among children It is estimated that 665,000 child deaths, or 5.5%, are related to zinc deficiency |
| Folic acid deficiency | Access to adequate folic acid supplementation is estimated to reduce the incidence of neural tube defects, affecting up to 5 babies per 1000 live births worldwide; 95% of cases occur from a first pregnancy |
Maternal Undernutrition and Consequences
Maternal undernutrition remains a ubiquitous problem in developing countries, where women usually do not have equal access to food, health care, and education. The nutritional status of a woman before, during, and after pregnancy is critically important for a healthy pregnancy outcome for both mother and baby. Years of neglect causes many women to remain undernourished at birth, stunted during childhood, pregnant during adolescence, as well as underfed and overworked during pregnancy and lactation. Undernutrition undermines the woman’s ability to survive childbirth and give birth to healthy children, translating into lost lives of mothers and their infants. In the developing world it impairs their productivity, income-generating capacity, and their contribution to their families, communities, and nations. Most women living in developing countries experience various biologic and social stresses that increase the risk of malnutrition throughout life. These stresses include food insecurity and inadequate diets, recurrent infections, poor health care, heavy work burdens, and gender inequities. These factors are compounded by high fertility rates, repeated pregnancies, and short intervals between pregnancies.
Low maternal body mass index
Maternal undernutrition is usually determined by body mass index (BMI; calculated as the weight in kilograms divided by height in meters squared, ie, kg/m 2 ) and fetal undernutrition reflected by intrauterine growth retardation (IUGR). A BMI of 17 to 18.49 is classified as underweight and a BMI of 18.5 to 24.99 is considered desirable. In adult women, a BMI of less than 18.5 is used as an indicator of chronic energy deficiency, which ranges from 10% to 19% in most countries. Almost 20% of women in sub-Saharan Africa, South Central and Southeastern Asia, and Yemen ( Fig. 3 ) have a BMI of less than 18.5. In India, Bangladesh, and Eritrea, 40% of women have low BMI; this has an adverse effect on pregnancy outcomes and increases the risk of infant mortality. The high proportion of women falling below the cut-off value in developing countries shows that maternal undernutrition is a staggering problem, which can lead to major consequences including increased rates of infection due to low immunity, increased risk of obstructed labor because of disproportion between the size of the baby’s head and the space in the birth canal, as well as increased risk of mortality due to obstructed labor. It also increases the risk of giving birth to a low birth weight (LBW) baby, which itself is a major risk factor of neonatal and infant mortality. Studies have shown that low maternal BMI is highly associated with IUGR, but at the same time it does not increase the risk of assisted delivery and pregnancy complications.
Distribution of intrauterine growth retardation
Undernutrition occurs during pregnancy, childhood, and adolescence, and has a cumulative negative impact on the birth weight of future babies. IUGR represents 23.8%, or approximately 30 million newborns per year. It is estimated that at least 13.7 million infants are born every year at term with LBW (weighing <2.5 kg at birth), representing 11% of all newborns in developing countries. IUGR is most common in South Central Asia, where 20.9% of newborns are affected; this subregion accounts for about 80% of all affected newborns worldwide. LBW is also common in Middle and Western Africa, where 14.9% and 11.4% of infants are LBW at term, respectively. Maternal nutritional factors account for approximately 50% of IUGR in developing countries. Studies have shown the close association of IUGR and early childhood growth patterns on disease and human capital. Studies from developing countries such as India, Pakistan, and Nepal shows the risk of neonatal deaths associated with IUGR Poor fetal growth, although not the direct cause of neonatal death, increases the risk of birth asphyxia and serious infections such as sepsis, pneumonia, and diarrhea ( Table 3 ).
| Low Birth Weight % (<2500 g) | IUGR-LBW (Estimated %) | IUGR-LBW % (2000–2499 g) | IUGR-LBW % (1500–1999 g) | |
|---|---|---|---|---|
| Africa | 14.3 | 8.89 | 7.85 | 1.04 |
| Asia | 18.3 | 12.39 | 10.94 | 1.45 |
| Latin America | 10 | 5.29 | 4.67 | 0.62 |
| All developing countries | 16 | 10.81 | 9.55 | 1.26 |
Maternal Micronutrient Deficiencies
Malnutrition among women manifests itself at the macronutrient and/or micronutrient level. Although micronutrient deficiencies of iron, iodine, and others are highly prevalent among women in many developing countries, zinc and vitamin A deficiencies contribute to the largest disease burden among micronutrient deficiencies among women of reproductive age.
Maternal iron deficiency
Iron deficiency and iron deficiency anemia are major public health problems, affecting an estimated 30% of the world’s population, affecting mostly women of reproductive age and young children. The major clinical manifestation of iron deficiency is anemia or low blood hemoglobin concentration. Anemia affects nearly half of all pregnant women in the world, and is a risk factor for maternal morbidity and mortality. More than 90% of affected women and children live in developing countries where parasitic infections and malaria are the 2 major causes of iron deficiency. Iron deficiency, resulting in anemia, is highly prevalent in women in developing countries and increased requirements are often not met by changes in diet. During pregnancy iron requirements increase substantially, due to increased requirements by the placenta and the fetus, compounded by blood loss at delivery. Iron deficiency increases the risk of mortality among anemic women caused by hemorrhage, which remains a leading cause of maternal death in developing countries, accounting for approximately 25% of all maternal deaths.
Zinc deficiency
Zinc plays a role in a large number of metabolic synthetic reactions. During periods of rapid growth and higher micronutrient requirements, such as infancy, adolescence, and late pregnancy, children and women are most susceptible to zinc deficiency. Prevalence of zinc deficiency in developing countries is probably similar to that of nutritional iron deficiency because the same dietary pattern induces both, with high prevalence in South Asia, most of sub-Saharan Africa, and parts of Central and South America. A high proportion of pregnant women in developing countries are likely to be at risk of zinc deficiency because of habitually inadequate zinc intakes. Maternal zinc deficiency has negative health consequences for women and their infants. Women with low plasma zinc concentrations have 3 to 7 times higher risk of premature rupture of membranes, 2 to 9 times higher risk of prolonged second-stage labor, increased risk of preterm delivery and LBW, and increased risk of maternal and infant mortality. Studies conducted in developing countries have shown the benefits of zinc supplementation during pregnancy on the child’s immune function, as well as reducing diarrhea and respiratory illnesses in infancy.
Vitamin A deficiency
Vitamin A is a micronutrient that has an important influence on the health of pregnant women and the fetus. Studies have shown that vitamin A deficiency is widespread throughout the developing world. Vitamin A deficiency has long been recognized in much of South and Southeast Asia (India, Bangladesh, Indonesia, Vietnam, Thailand, and the Philippines) by the common presentation of clinical cases of xerophthalmia, mostly in the latter half of pregnancies. In various studies, vitamin A deficiency has been associated with increased risk of morbidity and mortality from diarrhea and measles. Breast milk is a natural source of vitamin A and is the best way to protect a newborn from vitamin A deficiency. Poor maternal vitamin A status affects its concentration in breast milk.
Folic acid deficiency
In developing countries, pregnant and lactating women are at increased risk of folic acid deficiency because their dietary folic acid intake is insufficient to meet their physiologic requirements. Maternal folic acid deficiency is associated with megaloblastic anemia because of the role of folic acid in DNA synthesis. Folic acid deficiency interferes with DNA synthesis, causing abnormal cell replication. Low folic acid levels around the time of conception may cause neural tube defects in infants. Folic acid supplementation of women during the periconceptional period reduces the incidence of neural tube defects such as anencephaly and spina bifida. Low folic acid levels during pregnancy are associated with an increased risk of LBW babies.
Riboflavin deficiency
Riboflavin deficiency is endemic in populations that exist on diets lacking dairy products and meat. The effect of energy intake on riboflavin requirement in developing countries has not been studied. Despite this lack of data, a 10% increase in riboflavin requirement is suggested to cover the increased energy use during pregnancy, and a small increase is needed to cover the inefficiencies of milk production. For lactating women an estimated 0.3 mg of riboflavin is transferred in milk daily and, because milk production is assumed to be 70% efficient, the value is adjusted upward to 0.4 mg daily.
Iodine deficiency
Some 20 million children in developing countries are affected by iodine deficiency each year, and every single case could be easily prevented with the use of iodized salt. According to World Health Organization (WHO) estimates, the number of countries where iodine deficiency is a public health problem was reduced to 54 in 2003, from 110 in 1993, showing the effectiveness of the universal salt iodization strategy. Iodine is required for the synthesis of thyroid hormones that in turn are required for the regulation of cell metabolism throughout the life cycle. This problem is most serious in pregnant women and young children. During pregnancy, iodine deficiency adversely affects fetal development. Extreme iodine deficiency may cause fetal death or severe physical and mental growth retardation, a condition known as cretinism, which affects people living in iodine-deficient areas of Africa and Asia. The potential adverse effects of mild to moderate iodine deficiency during pregnancy are unclear. It can cause a range of problems referred to as iodine deficiency disorders (IDD): fetal loss, stillbirth, goiter, congenital anomalies, and hearing impairment. The mental retardation resulting from iodine deficiency during pregnancy is irreversible. Serious iodine deficiency during pregnancy may result in stillbirths, abortions, and congenital abnormalities such as cretinism. Endemic cretinism can be prevented by the correction of iodine deficiency, especially in women before and during pregnancy.
Vitamin D deficiency
Maternal vitamin D deficiency is a widespread public health problem, especially in the developing world. Vitamin D deficiency during pregnancy has been linked with several serious short- and long-term health problems in offspring, including impaired growth, skeletal problems, type 1 diabetes, asthma, and schizophrenia. Animal milk, which is the major source of vitamin D and calcium, is an expensive food in the developing world. With high prevalence of vitamin D deficiency and poor dietary calcium intake, the problem is likely to worsen during pregnancy because of the active transplacental transport of calcium to the developing fetus. Vitamin D deficiency during pregnancy has important consequences for the newborn, including fetal hypovitaminosis D, neonatal rickets and tetany, and infantile rickets. Many studies in developing countries are highlighting the high prevalence of vitamin D deficiency in certain groups, especially adolescent girls and pregnant and lactating women. A high dose of vitamin D during lactation may increase the vitamin D concentration in breast milk to levels sufficient to maintain vitamin D adequacy, and prevent rickets in the suckling infant.
Multiple micronutrient deficiencies
Many population groups in the developing world suffer from multiple nutrient deficiencies. Vitamin A, zinc, iron, and iodine have been mentioned, but there are many more significant overlaps. Given the fact that for those at certain stages of the life cycle—especially during pregnancy—changes in dietary habits are insufficient to meet micronutrients requirements, multiple micronutrient supplementations hold clear potential to address multiple nutrient deficiencies in a cost-effective manner. The breast milk of undernourished lactating women consuming a limited range of foods and with multiple micronutrient deficiencies is most likely to be low in concentrations of vitamin A (retinol), the B vitamins, iodine, and selenium. Deficiencies of vitamin B12, folate, vitamin B2 (riboflavin), and several other micronutrients can also contribute to anemia.
Child Undernutrition
The fortunes of children in the developing world have also been mixed in terms of their nutritional status. Malnutrition is one of the biggest health challenges that developing countries are facing in the twenty-first century, and the consequences for child health are enormous. The 3 main indicators of malnutrition in children are IUGR, wasting (including SAM), and stunting (low height for age). Whereas approximately 3.5% of children younger than 5 years in developing countries suffer from SAM, moderate acute malnutrition and chronic malnutrition typically affect about 10% to 30% of children younger than 5 ( Fig. 4 ).
Childhood stunting
Most growth failure occurs from before birth until 2 to 3 years of age. A child who is stunted at 5 years is likely to remain stunted throughout life. An estimated 32% of all children younger than 5 years are stunted in all developing countries, with Eastern and Middle Africa having the highest prevalence. India has around 61 million stunted children (34% of global estimate) with a prevalence of 51%. As shown in Table 3 , around 32% of children in all of the developing world had a height-for-age Z score of less then −2 in 2005 with the highest burden in Eastern and Middle Africa, where 50% and 42%, respectively, are stunted. Overall, with a child-stunting prevalence of 40% or more in developing countries, 23% are in Africa and 16% are in Asia. Among 52 countries where stunting prevalence is less than 20%, 17% are in Latin America, 16% are in Asia, 11% in Europe, and 4% each in Africa and Oceania ( Table 4 ).
| Children <5 Years in Million | % Stunted (95% CI) | Number Stunted in Millions (95% CI) | % Severely Wasted (95% CI) | Number Severely Wasted in Millions (95% CI) | Percentage Underweight (95% CI) | Number Underweight in Millions (95% CI) | |
|---|---|---|---|---|---|---|---|
| Africa | 141.914 | 40.1 (36.8–43.4) | 56.9 (52.2–61.6) | 3.9 (2.2–5.7) | 5.6 (3.0–8.0) | 21.9 (18.8–24.0) | 31.1 (28.1–34.0) |
| Asia | 356.879 | 31.3 (27.5–35.1) | 111.6 (98.1–125.1) | 3.7 (1.2–6.2) | 13.3 (4.4–22.3) | 22.0 (18.5–25.6) | 78.6 (65.9–91.3) |
| Latin America | 56.936 | 16.1 (9.4–22.8) | 9.2 (5.3–13.0) | 0.6 (0.2–1.0) | 0.3 (0.1–0.6) | 4.8 (3.1–6.4) | 2.7 (1.8–3.7) |
| All developing countries | 555.729 | 32.0 (29.3–34.6) | 177.7 (162.9–92.5) | 3.5 (1.8–5.1) | 19.3 (10.0–8.6) | 20.2(17.9–22.6) | 112.4 (99.3–125.5) |
Infectious diseases such as diarrhea, pneumonia, measles, and malaria are both major causes and effects of malnutrition, and can lead to growth retardation ( Fig. 5 ).
Wasting and severe acute malnutrition
Wasting refers to low weight for height, whereby a child is thin for his or her height but not necessarily short. Also known as acute malnutrition, this carries an immediate increased risk of morbidity and mortality. Wasted children have a 5 to 20 times higher risk of dying from common diseases such as diarrhea or pneumonia than normally nourished children. Asia has the highest prevalence (16%) of wasting, which affects 55 million children globally. South Central Asia and Middle Africa have the highest percentage of children with severe wasting ( Fig. 6 ).
SAM is defined as a weight-for-height measurement of 70% or less below the median, or 3 standard deviations or more below the mean National Center for Health Statistics reference values, the presence of bilateral pitting edema of nutritional origin, or a mid-upper-arm circumference of less than 110 mm in children age 1 to 5 years. Thirteen million children younger than 5 years have SAM, and the disorder is associated with 1 to 2 million preventable child deaths each year. Severely malnourished children make up approximately 1% to 3% of the population of children younger than 5 in many African and Asian countries. About 9% of sub-Saharan African and 15% of South Asian children have moderate acute malnutrition, and about 2% of children in developing countries have SAM. This figure is equivalent to approximately 1.5 million child deaths associated with severe wasting and 3.5 million child deaths associated with moderate wasting every year. These figures do not include children who die of edematous malnutrition (kwashiorkor), a form of SAM that is more common in some countries. In India alone, 2·8% of children younger than 5 years (more than 5 million children) are severely wasted and in many poor countries, SAM is the most common reason for pediatric hospital admission.
In developing countries, SAM poses a great threat to the health of infants and children. Many advanced cases of SAM are complicated by concurrent infective illness, particularly acute respiratory infection, diarrhea, and gram-negative septicemia ( Fig. 7 ). Parental illiteracy is found to be associated with a higher risk of SAM. This feature is observed by many studies carried out in the developing world. Similarly, poor family income and larger family size are other risk factors associated with SAM found in different studies. The severity of SAM, its prognosis, and the determinants of successful treatment are primarily dependent on the lead time to presentation.
Underweight
Underweight refers to low weight for age, when a child can be either thin or short for his or her age. Underweight reflects a combination of chronic and acute malnutrition. Twenty percent of children younger than 5 year in the developing world had a weight-for-age Z score of less then −2 in 2005, with the highest burden in South Central Asia (33%) and Eastern Africa (28%). The percentage of underweight children in the developing world, due to malnutrition, declined from 35% in 1980–1994 to 27% in 1995–2001 ( Table 5 ).
| Regions | 1980–1994 | 1990–1997 | 1995–2002 |
|---|---|---|---|
| South Asia | 64 | 51 | 46 |
| Sub-Saharan Africa | 31 | 30 | 29 |
| East Asia | 23 | 20 | 17 |
| Latin America and Caribbean | 11 | 10 | 8 |
| Middle East and North Africa | 12 | 17 | 14 |
| Developing countries | 35 | 30 | 27 |
Micronutrient deficiencies in children
Micronutrient deficiencies have serious repercussions for the developing fetus and for children. If iodine deficiency disorders may cause fetal brain damage or stillbirth, folate deficiency may result in neural tube or other birth defects and preterm delivery. Similarly, both iron deficiency anemia and vitamin A deficiency may have significant effects for the future infant’s morbidity and mortality risk, vision, and cognitive development ( Table 6 ).
| Factor | DALYs Lost Percentage | ||
|---|---|---|---|
| Direct effect | At risk factor | Total | |
| General malnutrition | 1.0 | 14.0 | 15.0 |
| Micronutrient deficiencies | 9.0 | 8.5 | 17.5 |
| Total | 10.0 | 22.5 | 32.5 |
Iron deficiency
For children, health consequences include premature birth, LBW, infections, and elevated risk of death. Later, physical and cognitive development are impaired, resulting in lowered school performance. The major cause of iron deficiency in children of developing countries is the unavailability to the poor of food such as meat, fish, or poultry.
Zinc deficiency
Zinc deficiency is highly prevalent in South Asia followed by sub-Saharan Africa and South America, and the prevalence of stunting is one of the clinical manifestations of zinc deficiency. Countries where stunting prevalence is more than 20% are at higher risk for zinc deficiency. Zinc has no tissue reserves, unlike vitamin A and iron, and its turnover is rapid, especially during common gastrointestinal infections. Young children in developing countries who have a poor diet and high exposure to gastrointestinal pathogens are at greatest risk of zinc deficiency. Zinc deficiency in children increases the risk of diseases such as diarrhea, pneumonia, and malaria worldwide. The relative risk of morbidity associated with zinc deficiency is 1.09 for diarrhea, 1.25 for pneumonia, and 1.56 for malaria. Studies from Nepal, Bangladesh, and Zanzibar have shown the relative risk estimated at around 1.29 for diarrhea, 1.18 for pneumonia, and 1.11 for malaria for mortality in infants aged 1 to 59 months.
Vitamin A deficiency
It is estimated that around 250 million children younger than 5 years have vitamin A deficiency. Within developing countries, Bangladesh, India, Indonesia, and the Philippines appear to be the most afflicted, but many countries in Africa and some in Central and South America have the same problem. Vitamin A plays an important role in the maintenance of mucous membranes, thus enhancing local resistance to penetration of viruses and bacteria. The most vulnerable group is children from birth to 5 or 6 years of age, peaking between 2 and 3 years old. A child with vitamin A deficiency faces 25% greater risk of dying from several childhood diseases such as measles, malaria, or diarrhea. Increasing evidence now shows that improving vitamin A status among preschool children increases their chances of survival by as much as 30%. Vitamin A deficiency is the most common cause of blindness in children in many endemic areas. Xerophthalmia occurs almost entirely in children living in poverty. It has been especially prevalent in children of poor rice-eating families in South and Southeast Asia. There is a high incidence in some African countries, whereas other countries, especially in West Africa, seem to have a lower prevalence, in part because of the consumption of red palm oil, which is high in carotene. The supplementation of vitamin A reduced overall child mortality by 23%, with a 50% reduction for those infected with measles. Studies have also shown the increased risk of mortality with vitamin A deficiency, with relative risk of 1.47 for diarrhea and 1.35 for measles.
Riboflavin deficiency
The major cause of riboflavin deficiency is inadequate dietary intake. If maternal status is poor during gestation, the infant is likely to be born riboflavin deficient. Riboflavin deficiency among schoolchildren has been documented in many developing countries where the intake of milk products and meat is limited. It mostly occurs in combination with a deficiency of other B-complex vitamins. More advanced deficiency may result in cheilosis, angular stomatitis, dermatitis, corneal vascularization, anemia, and brain dysfunction.
Iodine deficiency
Relatively few child deaths are attributed to iodine deficiency, but it causes considerable loss of DALYs. According to the WHO, global iodine deficiency disorders were estimated to result in the loss of 2.5 million DALYs with 25% of this burden occurring in Africa alone. Insufficient intake of iodine can result in impaired intellectual development and physical growth. Iodine-deficient children usually experience mild mental retardation. Cretinism, caused by severe deficiency, is associated with extreme mental retardation.
Calcium and vitamin D deficiency
Although fetuses are relatively protected from maternal deficiency of calcium, calcium deficiency rickets can result from low intake in young children. It is the main cause of rickets in Africa and parts of Asia, due to shrouding, inadequate exposure to sunlight, and lack of intake of a diet fortified with Vitamin D. In developing countries of Asia, Africa, and Latin America, the calcium content of complementary foods provided to children during the first year of life is much less than the 50% that is suggested. In India alone the daily calcium intake of children varies from 314 mg to 713 mg. Similarly, low calcium intakes have been reported from Kenya (314 mg/d), South Africa (463 mg/d girls, 528 mg/d boys), Ghana, Nigeria (214 mg/d), Malaysia, and China (374 mg/d urban, 324 mg/d rural). Thirty-five to fifty percent of children are vitamin deficient in India, China, Lebanon, and Libya. Nutritional rickets is highly prevalent in many developing countries and is relatively high in Africa, East Asia, and South Asia. In fact, rickets is now said to be the most common noncommunicable childhood disease in the world.
Multiple micronutrient deficiencies
Micronutrient deficiencies are more likely in children who consume diets that are poor in nutritional quality, or who have higher nutrient requirements due to high growth rates and/or the presence of bacterial infections or parasites, which are common findings in the developing world. In particular, a diet that is low in animal-source foods typically results in low intakes of iron, zinc, calcium, retinol (preformed vitamin A), vitamin B2 (riboflavin), vitamin B6, and vitamin B12. Often, poor-quality diets also lack fresh fruits and vegetables, which mean that intakes of vitamin C (ascorbic acid) and folate will also be inadequate. Improving status in one micronutrient, or even several micronutrients simultaneously in the case of multiple deficiencies, can have wider benefits to health of children in developing countries.
Risk factors
Of the various risk factors recognized to affect undernutrition, the following are key.
Poverty and Food Insecurity
Extreme poverty remains an alarming problem in the world’s developing regions. The causes of poverty include poor people’s lack of resources, an extremely unequal income distribution in the world and within specific countries, conflict, and hunger itself. The high prevalence of undernutrition in developing countries is the result of a number of factors of which first and foremost is the presence of chronic poverty. The lack of purchasing power of people and increased population growth rates negatively affect the nutrition of the people. Poverty status had a statistically significant effect on LBW, the neonatal mortality rate, and the maternal mortality rate in developing countries (see Fig. 7 ).
Nutrition, health, and education are interrelated and mutually supporting. Inadequate nutrition in children affects long-term physical and mental development and, therefore, productivity later in life. By causing poor health, low levels of energy, and even mental impairment, hunger can lead to even greater poverty by reducing people’s ability to work and learn. Education of mothers can affect the nutrition of their children, as a well-educated mother knows what food to give to her children and how to prepare it.
Household food insecurity is one of the possible underlying determinants of malnutrition. A high percentage of household expenditure allocated to food is a major indicator of household food insecurity in developing countries. The best estimates of micronutrient malnutrition by the WHO indicate that the total number of people at risk of one or more of the deficiencies is around 2 billion, most of whom live in the developing countries. Persistence of malnutrition globally or increases in incidence will further imperil the socioeconomic conditions of the developing world shown by these figures, and have profound implications in today’s global economic crisis.
Micronutrient deficiencies also affect displaced populations with high prevalence. For example, iron deficiency has been found with a prevalence of 23% to 75% in child refugee camps in Africa, and this deficiency contributed to the high prevalence of anemia found in many studies. Many of the world’s developing countries are locked in a tragic and vicious circle of poverty and conflicts, which have reversed development and increased global poverty levels. Children are most vulnerable to the consequences of displacement and conflicts. In many developing countries displacement and food insecurity also increase the risk of micronutrient deficiency disorders (ie, iron, iodine, and B-complex deficiencies, especially thiamine, riboflavin, and niacin), and communicable diseases are known to rapidly deplete vitamin A stores. Malnutrition contributes to physical and mental impairment in children younger than 5 years. Malnutrition undermines immune-response mechanisms and resistance to infections, thus contributing to an increase in incidence, duration, and severity of illnesses. Severely malnourished children are 8 times more likely to die from infection. Measles, diarrheal disease, acute respiratory infections (ARIs), and malaria (where malaria is endemic) with malnutrition as an underlying and aggravating factor account for 51% to 95% of all reported causes of morbidity and mortality among displaced populations (WHO and UNICEF, 2002). Malaria and ARIs, including pneumonia, are responsible for the deaths of many children. Similarly, diarrhea is another common and often deadly disease. Cholera is a constant threat, as exemplified in refugee camps in Bangladesh, Kenya, Malawi, Nepal, Somalia, Zaire, and Afghanistan.
During conflicts, mothers may experience hunger, exhaustion, and distress that can make them less able to care for their children. Breastfeeding may be endangered by the mother’s loss of confidence in her ability to produce milk. The general disruption in routine can separate mothers from their children for long periods, as social structures and networks break down. Knowledge about breastfeeding is passed from one generation to the next, and this can be lost when people flee and families are broken up. Yet artificial feeding, risky at all times, is even more dangerous in unsettled circumstances.
Inadequate Feeding Practices
The first 2 years of life are a crucial window during which to break the vicious cycle of undernutrition. After birth, early and exclusive breastfeeding for 6 months followed by the introduction of complementary feeding is essential to improve the health and survival of newborns and children. Breastfeeding is important not only for the optimal growth and development, but also has a protective role in decreasing the incidence and severity of infectious diseases, and decreases the risk of morbidity and mortality in young children. In the developing world, lack of knowledge and awareness about feeding the infant together with influences of various cultural beliefs and food taboos interfere with the feeding of infants, leading to malnutrition with a high incidence of infant morbidity and mortality. Breastfeeding provides ideal nutrition for infants and reduces the incidence and severity of infectious diseases, and also contributes to women’s health. In most developing countries, women spend a large proportion of their reproductive years pregnant, lactating, or pregnant and lactating. In Asia, Africa, Latin America, and the Caribbean, only 47% to 57% of infants younger than 2 months are exclusively breastfed and for children 2 to 5 months this percentage falls to 25% to 31%. The nutritional demands to support fetal growth and breast milk production during pregnancy and lactation are multiple. Breast milk completely provides the infant’s nutritional and fluid needs for about the first 6 months of life. For first 6 months, infants should not receive any prelacteal feed such as water, other liquids, or ritual foods to maintain good hydration, not even in hot and dry climates (exclusive breastfeeding). In many developing countries exclusive breastfeeding is virtually nonexistent. Mothers tend to discard the first milk (colostrum), substituting prelacteal feeds such as honey, sugar water, or oil instead of the breast milk as the first feed for all newborn babies. Initiation of breastfeeding usually takes place on the third or fourth day after birth. Complementary feeding is also regarded as defective because of ignorance, lack of awareness, and influences of cultural beliefs, and consists of bulky, energy-thin feeds, with weaning occurring either too early or too late. Effective programs promoting complementary feeding could reduce deaths of children younger than 5 years in developing countries.
High Disease Burden and Inadequate Management
Undernutrition in children makes them susceptible to low immune function and confers a higher risk of developing illnesses such as diarrhea and pneumonia. It has been estimated that around 50% to 70% of the burden of diarrheal diseases, measles, malaria, and lower respiratory tract infections in childhood are attributable to undernutrition.
Globally, ARIs kill more children younger than 5 years than any other infectious disease, accounting for almost 2 million deaths a year in this age group. Ninety-nine percent of these deaths occur in developing countries. ARIs cover the spectrum of infectious illnesses of the respiratory tract, ranging from mild upper respiratory infections to serious infections of the lower respiratory tract (bronchiolitis and pneumonia). Severe ARIs are responsible for a great deal of the morbidity and mortality suffered by children in the developing world. Many risk factors have been recognized in the development of severe ARI, including age less than 1 year, malnutrition, vitamin A deficiency, LBW, lack of breastfeeding, crowding, and exposure to indoor pollutants. Without early treatment children can die very rapidly. Early recognition of ARIs is also essential for effective treatment. In malnourished children, pneumonia and ARI must be treated in a place where intravenous antibiotics can be administered.
Poor water and sanitation in developing countries is responsible for 4 billion diarrheal diseases, mostly in children younger than 5 years. In addition, diarrheal illnesses account for an estimated 12,600 deaths each day in children in developing countries in Asia, Africa, and Latin America. Diarrheal diseases lead to decreased food intake and nutrient absorption, malnutrition, reduced resistance to infection, and impaired physical growth and cognitive development. There is a bidirectional relationship between malnutrition and diarrheal diseases. There is now evidence that therapeutic use of specific nutrients early in some acute illnesses like diarrhea may reduce episode severity and duration as well as case fatality. The most effective intervention to treat diarrhea is early rehydration along with appropriate nutrition. Cases of severe dehydration need to be treated with oral rehydration therapy or intravenous fluids. However, improved diarrheal outcomes with zinc therapy, and reduced severity and duration in acute and persistent diarrhea, are now well established and may help reduce the nutritional issues associated with diarrhea.
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