Childhood malnutrition—both the timeless scourge of the various forms of undernutrition as well as the exploding epidemic of obesity that is the hallmark of overnutrition—is arguably the most important disease cluster in pediatrics, given our discipline’s all-encompassing emphasis on the optimal growth and development of children and the essential role of nutrition in the optimal functioning of all other organ systems. Childhood malnutrition, in all its forms, contributes to the deaths of no less than 45% of all children younger than 5 years of age worldwide (under-5 mortality). Decreasing maternal, prenatal, infant, and childhood malnutrition remain among the highest priorities for improving child health worldwide, an effort that obligates pediatricians to look beyond the individual patient and to work toward the greater health of entire societies and communities. The vast majority of the world’s undernourished children live in low- and middle-income countries, predominantly in sub-Saharan Africa and South Asia, emphasizing the pervasive link between poverty and malnutrition.
Undernutrition, Infection, and the Gut
Most profoundly, undernutrition and acute infectious diseases both exacerbate each other, leading to a vicious cycle of impaired growth, high rates of infection-related morbidity, and unacceptably high rates of early mortality. When considering the global mortality attributed to undernutrition and infectious diseases, aggregate estimates of deaths are far larger than the actual observed deaths worldwide. That is because 2 coincident conditions, such as a nutrient deficiency and a microbial infection, may lead to death; however, when these conditions occur in isolation, death does not occur. Thus, a child’s death may be attributed to both the nutrient deficiency and the microbe, and counted as 2 deaths. Rather than see this as “double-counting” or overestimating mortality, it is better to consider this as 2 opportunities to save the child’s life.
At the center of this balance lies the gut, which acts not only as the agent of nutrient absorption, but also as the symbiotic host of the enteric microbiome and the most intimate interface between the immune system and the environment. In order to ensure adequate absorption and bioavailability of all the essential nutrients in the diet, the gut must properly balance inflammation such that acute infections are controlled but that a chronic catabolic state is avoided.
Risk Factors and Mechanism
The pathway to undernutrition begins in the prenatal period with undernourished mothers, with gestations often marked by relative food insecurity, poor micronutrient intake, and intermittent infections such as malaria, leading to growth retardation. Affected infants are thus more likely to be born premature, underweight, and short for gestational age, and have small head circumferences for their gestational age. This physical stunting often continues through the rest of the critical 1000-day window encompassing pregnancy through the first 2 years of life. During this time, the ...