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The complexity and mystery of linear growth

Student Blogger for Global Nutrition Council at ASN’s Scientific Sessions and Annual Meeting at EB 2016

By: Sheela Sinharoy, MPH

A symposium called Biology of Linear Growth on Tuesday examined linear growth from the molecular to the population level, bringing perspectives from biology, physical anthropology, nutrition, and epidemiology

Are you familiar with the process of endochondral ossification? Julian Lui, MD PhD explained that this is the process that results in linear growth. It takes place in the growth plates, at the end of long bones such as the femur, and is subject to systemic regulation by endocrine, nutritional, and inflammatory cytokine factors as well as local regulation by paracrine factors and other cellular mechanisms. Malnourished children have lower levels of hormones like insulin-like growth factor 1 (IGF-1) and estrogen, as well as increased levels of glucocorticoids, leading to decreased linear growth. Dr. Liu explained that this allows the body to conserve resources and that, in situations of food insecurity, “Growth is something of a luxury that can be postponed until better times.”

Rather than growing continuously, children grow in saltations, meaning that – as many a parent has observed – a child may grow substantially overnight and then not at all for a number of days afterwards. Michelle Lampl, MD PhD stated that as children age, these saltations become less and less frequent, with older children growing much less often than infants. The amount and frequency of these growth saltations can be affected by environmental factors, which can interact with cellular effects. Maternal smoking, for example, has a well-documented inhibitory effect on growth, as does maternal alcohol consumption and stress.

Since linear growth happens most rapidly in early life, the first 1,000 days from conception to two years of age are considered a critical period. Parul Christian, DrPH presented results from a meta-analysis analyzing various maternal and child nutrition interventions targeting this 1,000-day window. Starting during pregnancy, balanced protein-energy, iron-folic acid, and multiple micronutrient supplementation were all found to increase birth weight. However, maternal supplementation during pregnancy was not associated with any long-term linear growth in children under five years old. For infants and young children, nutrition promotion and food supplementation showed promise as interventions with positive impacts on child height.

In the final talk of the symposium, Aryeh Stein, PhD addressed the question of linear catch-up growth: for those children whose growth has been suppressed by malnutrition, is it possible to catch up on missed growth, even after the first 1,000 days? A number of studies have provided different nutrients and foods to children ages two and older. Dr. Stein presented results from studies of protein, zinc, iron, iodine, calcium, multiple micronutrients, and food. Protein and some of the micronutrients may have promise, but several of the calcium studies reported negative effects, while food had no association with growth.

The symposium made it clear that nutrition has an important role to play in stimulating or inhibiting linear growth. However, a great deal remains to be learned about these complex biological processes and the most effective interventions to promote children’s optimal growth.

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Why Economists are making the Case for Stunting Reduction

By Marion Roche, PhD

Approximately 162 million children are stunted.In the global nutrition community the human costs of stunting are well recognized: stunted children complete less school, have less learning and earning opportunities, and females who become moms in the future are more likely to give birth to stunted children. Intervening early in 1000-day window (from conception to the age of two) and even earlier, pre-pregnancy, is recognized as most cost-effective way to prevent, as in many settings it challenging to reverse the physical and cognitive deficits from chronic malnutrition. Beyond the human costs, there is also an economic case to be made for investing in stunting reduction.

Every four years, the world’s leading economists and experts from diverse development fields come together to rank the best investments for development in what is called the Copenhagen Consensus. Nutrition is one such investment that is consistently ranked as a “best buy”. Specific interventions such as vitamin A supplementation, salt iodization, zinc & ORS for diarrhea treatment and support for breastfeeding and adequate complementary feeding have all been in the top 10 best investments in previous years. In addition, nutrition-sensitive approaches, such as keeping girls in school, improvements to agriculture yields and crop quality, enabling gender equity for women, and overall poverty reduction, are all necessary to sustainable long-term stunting reductions for communities and countries.

This month, world leaders and experts met in Addis Ababa, Ethiopia for the Third International Financing for Development conference. A presentation by Dr. Meera Shekar of the World Bank and Dr. Robert Hetch of Results for Development at an MI co-hosted side-event on nutrition at the conference laid out what it would take to achieve the World Health Assembly target of reducing stunting by 40% by 2025. They emphasized that strategic investing in improving the nutrition situation for 68 million children would offer a long-term $45 dollar return on each dollar invested. More specifically, every dollar invested in reducing stunting is estimated to generate an $18 return in the long run. However, although many nutrition interventions look affordable on an individual scale, a more detailed analysis has been done to show what it would cost to deliver these interventions and reduce stunting at a global scale.

The Financing for Development conference was centred on funding the Sustainable Development Goals, the set of targets relating to the of future international development post-2015. Looking at the return on investment (ROI) in nutrition and knowing that nutrition has such a profound effect on other areas of a person’s life, I think there is no better investment the world can make to reach the SDGs more quickly and effectively than that in nutrition!