DECEMBER 13, 2013
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About the Authors:
Christopher B. Barrett is the Stephen B. and Janice G. Ashley Professor of Applied Economics and Management and International Professor of Agriculture in the Charles H. Dyson School of Applied Economics and Management, as well as Professor in the Department of Economics and Fellow of the David R. Atkinson Center for a Sustainable Future (ACSF), all at Cornell University, where he also serves as the Director of the Cornell Institute for International Food, Agriculture and Development’s initiative on Stimulating Agricultural and Rural Transformation, and served as the founding Associate Director for Economic Development programs for the ACSF. He holds degrees from Princeton (AB, History, 1984), Oxford (MS, Development Economics, 1985) and the University of Wisconsin-Madison (dual PhD, Economics and Agricultural Economics, 1994). He has held visiting professorships at Monash University and the University of Melbourne and directed summer seminar programs at Calvin College. At Cornell, he has taught undergraduate econometrics, a writing-in-the-majors course on Contemporary Controversies in the Global Economy, and Comparative Perspective on Poverty Reduction Policy, as well as graduate courses on the Microeconomics of International Development and Food Systems and Poverty Reduction; and he runs a graduate research seminar in Development Microeconomics. Professor Barrett has published or has in press 14 books and more than 260 journal articles or book chapters. He has served on a variety of boards; has won several university, national, and international awards for teaching, research, and public outreach; and is an elected Fellow of both of the Agricultural and Applied Economics Association and of the African Association of Agricultural Economists.
Leah Bevis is a fourth year PhD candidate in the Dyson School of Applied Economics and Management, and a Fellow of the Food Systems and Poverty Reduction IGERT program at Cornell University. She did her undergraduate degree at Middlebury College in Vermont where she majored in geography, minored in economics, and researched food desserts on her home island of Oahu, Hawaii, for her capstone project. After graduating from Middlebury and before moving to Ithaca, Leah spent a year in eastern Uganda running village-level health programs for a nonprofit organization called Uganda Village Project. Leah is interested in the problem of persistent poverty at the household level in Africa and the ways in which food systems and human capital accumulation affect persistent poverty. She is also particularly focused on childhood micronutrient malnutrition. Her dissertation research focuses on soil-to-human micronutrient transmission and soil degradation-based poverty traps in Uganda.
The Micronutrient Deficiencies Challenge in
African Food Systems
Per Pinstrup-Andersen was among the first to call attention to the “triple burden” of malnutrition that transcends insufficient dietary energy supply to encompass problems of overweight/obesity and micronutrient deficiencies. He has also been among the most articulate analysts of the complex linkages between producers, consumers and marketing intermediaries in food systems in developing countries. In this paper we celebrate Per’s insights in both of these dimensions with a review the oft-overlooked role of micronutrients in food security, and their relation to nutrition-related poverty traps, with an emphasis on the many entry points within food systems where micronutrients deficiencies might originate and be remedied.
’Hidden hunger” due to micronutrient deficiencies are widespread. Iron deficiency is thought to be the most common nutritional disorder worldwide (McDowell 2003), with about 2 billion people (or 30 percent of the global population) suffering from anemia. Iodine deficiency is considered the most common cause of preventable mental defects globally (Hetzel and Wellby 1997), even though over half of the world’s population has access to iodized salt. According to the WHO, Vitamin A deficiency is the leading cause of acquired blindness in children, and affects up to 21% of children under five. Food availability data suggest that at least one-third of the global population suffers from zinc deficiency (Hotz and Brown 2004), a condition characterized by stunting, impaired immune function, skin disorders, and cognitive dysfunction.
The widespread prevalence and stubborn persistence of micronutrient deficiencies is illustrated in Figure 1, which depicts the association between stunting, wasting, and a few micronutrient deficiency indicators and global national income (GNI) per capita via univariate logarithmic regression using the most current indicators available at country level in reasonably consistent form. Note the patterns of the most commonplace anthropometric indicators of nutritional performance: wasting and stunting. The prevalence of wasting, characterized by low weight-for-height and caused primarily by insufficient calorie and protein consumption, starts low and falls rapidly with growth in a country’s GNI. Stunting, characterized by low height-for-age and caused primarily by insufficient calories, iron, and zinc intake, is also highly responsive to income. By contrast, indicators of micronutrient deficiency appear much less responsive to growth in GNI. With the exception of vitamin A deficiency, which declines at a rate similar to that of stunting, micronutrient deficiencies are much less responsive to growth in GNI per capita than are stunting and wasting prevalence indicators.
Why are micronutrient deficiencies so much less responsive to income growth than the clinical signs of under-nourishment on which workhorse measures of hunger and food insecurity are based? One interpretation of Figure 1 is that it suggests that while food consumption increases as income rises, leading to rapid increases improvements in standard anthropometric measures, intake does not always increase in ways that rapidly and effectively meet micronutrient requirements.
There are multiple prospective reasons for this, each related to different important features of food systems. Is this due to an informational problem, thus requiring consumer education and outreach at the downstream end of food value chains? Or is it a problem with food supply chain intermediaries that fail to preserve micronutrients in perishable products or to fortify with minerals and vitamins where feasible? Or is this the natural result of changing diets in response to income growth and changes in relative prices? Or does the issue, at root, revolve around agricultural production and the uneven or insufficient availability of essential micronutrients in soils and water?
It is possible that micronutrient malnutrition is simply not very responsive to income. But it is also possible that growth in GNI actually promotes micronutrient malnutrition in some ways even while it might reduce micronutrient malnutrition in others. For example, rising GNI is associated with a nutritional transition characterized broadly by the switch from traditional diets high in cereals and fiber to a more Western diet high in sugars, fats, and animal-source foods. This transition has the potential to reduce certain types of micronutrient consumption. Across much of the world, for example, wheat consumption is on the rise (Pingali 2006), and wheat consumed in a processed form may carry much less iron and zinc than many traditional staples.
In a similar vein, the Green Revolution of the 1970s was successful in promoting greater yields and decreasing hunger across much of the developing world. It may have simultaneously decreased micronutrient consumption, both by promoting high-calorie, low-micronutrient crops over lower-calorie, high-micronutrient crops, and also by encouraging agricultural practices that lower the micronutrient content of certain crops (Welch and Graham 1999; Graham et al. 2012). Even today, Green Revolution farming strategies become more feasible at higher income levels. Wealthier farmers are likely to employ soil amendments such as NPK fertilizers, which can both lower zinc uptake by plants and also reduce zinc translocation from leaves to seeds (Graham and Welch 2012). Furthermore, higher grain yields—which may both drive and be driven by higher income levels—are generally associated with lower iron content within grain (Graham et al. 2012).
Soils low in micronutrients such as zinc, iron, iodine, nickel or cobalt result in lower-micronutrient crops, and thus lower-micronutrient consumption by human populations. This might be especially true among those who consumer directly from their own or neighbors’ production, without intermediation by market intermediaries who might process and fortify commodities. This soil-to-human micronutrient transmission may account for a large portion of deficiencies; the global prevalence of both zinc deficiency and perhaps even iron deficiency may be largely explained by zinc deficient soils, for instance (Graham et al. 2012). Except in extreme cases such as Finland’s selenium-deficient soils or regions of China virtually devoid of soil iodine, public health experts and policy-makers largely ignore this phenomenon. But if the natural resources in agricultural production are an important root cause, rising national income will do little to mitigate micronutrient deficiencies in the absence of concerted plot-level efforts at soil nutrient amendment that are not being made currently.
Even if rising income does manage to increase the consumption of one micronutrient—for instance increased iodine consumption via iodized salt—it may do little to decrease deficiency levels if the uptake of that micronutrient depends on the levels of another. Uptake and efficacy of iodine, for instance, depends on levels of selenium. Thus, uptake of iodized salt may do little to decrease goiter and thyroid malfunction if a population remains selenium deficient (Kishosha et al. 2011). Similarly, iron deficiency may stem from an underlying zinc deficiency in many populations (Graham et al. 2012). Such synergies between micronutrients may, to some extent at least, differentiate micronutrient deficiency from the macronutrient deficiencies that cause wasting and stunting. Eating more, and especially more protein, will almost always address wasting. The same could almost be said of stunting, except in the case of underlying zinc deficiency, which can cause stunting even in otherwise health, well-fed children. This may explain, in fact, the fact that the stunting response rate to income in Figure 1 runs between the wasting and the micronutrient deficiency response rates.
These questions loom especially large within sub-Saharan Africa, where rates of micronutrient deficiency are high and remain only weakly responsive to increasingly rapid economic growth while diets and agricultural production systems evolve steadily.
Graham, Robin D., Marija Knez, and Ross M. Welch. 2012. How much nutritional iron deficiency in humans globally is due to an underlying zinc deficiency? Advances in Agronomy 115:1–40.
Graham, R. D., R. M. Welch, D. A. Saunders, H. E. Bouis, M. Bonierbale, S. deHaan, G. Burgos, G. Thiele, R. Liria, et al. 2007. Nutritious subsistence food systems. Advances in Agronomy 92:1–74.
Hetzel B.S., and M. L. Wellby. 1997. Handbook of Nutritionally Essential Minerals. O’Dell, B. L., and R.A. Sunde, eds. New York: Marecel Dekker, Inc.
Hotz, C., and K. H. Brown. 2004. Assessment of the risk of zinc deficiency in populations and options for its control. Food and Nutrition Bulletin25:S91–204.
Kishosha, P. A., M. Galukande, and A. M. Gakwaya. 2011. Selenium deficiency a factor in endemic goiter persistence in sub-Saharan Africa. World Journal of Surgery 35:1540–1545.
La Daniels, R. Gibson, and K. Simmer. 2000. Indicators of selenium status in Australian infants. Journal of Paediatrics and Child Health 36:370–374.
McDowell, L. R. 2003. Minerals in Animals and Human Nutrition. 2nd ed. Amsterdam: Elsevier Science B.V.
Mäkelä, A.-L., V. Näntö, P. Mäkelä, and W. Wang. 1993.The effect of nationwide selenium enrichment of fertilizers on selenium status of healthy Finnish medical students living in south western Finland. Biological Trace Element Research 36:151–157.
Murphy, S. P., Beaton, G. H., and D. H. Calloway. 1992. Estimated mineral intakes of toddlers: predicted prevalence of inadequacy in village populations in Egypt, Kenya, and Mexico. American Journal of Clinical Nutrition 56(3):565–572.
Pingali, Prabhu. 2006. Westernization of Asian diets and the transformation of food systems: Implications for research and policy. Food Policy 32:281–298.
Welch, R.M., and Robin D. Graham. 1999. A new paradigm for world agriculture: meeting human needs productive, sustainable, nutritious. Field Crop Research 60:1–10.
WHO. 2008. Worldwide prevalence of anaemia 1993–2005, WHO Global Database on Anaemia, World Health Organization, Edited by Bruno de Benoist, Erin McLean, Ines Egli and Mary Cogswell.
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