Environmental and Physiological Barriers to Child Growth and Development.

Aggregated analyses of child growth in low- and middle-income countries (LMICs) reveal a remarkably consistent picture of serious growth failure compared to the WHO reference growth curves. Impoverished diets with low dietary diversity are a key driver of poor growth, but there are important additional environmental factors that limit the uptake and utilization of nutrients. This paper considers such factors. A large proportion of the rapid growth deterioration in later infancy can be ascribed to infections and to wider nonspecific effects of living in an unhygienic environment, including the ingestion of toxins such as aflatoxin. Despite never revealing themselves as clinical syndromes, the great majority of children in rural low-income settings of Africa and Asia are antibody positive to numerous pathogens (CMV, EB, HepB, Helicobacter pylori, and many more) by 24 m; these infections must take their toll. Additionally, there is a syndrome widely termed environmental enteric disease that combines gut leakage with a chronic inflammation leading to nutrient losses and cytokine-mediated growth retardation. Systemic inflammation also inhibits nutrient uptake and utilization. Elimination of these environmental barriers will be key to achieving optimal child growth and development in LMICs.