Kamis, 02 Februari 2012

The Nutrition Transition: Diet and Disease in the Developing World

Evolution is transition. Fueled by ideas, war, scientific breakthroughs, and chance, the relationship of humans with their environment is in constant change, in an endless quest for equilibrium. Food, as a central component of survival, has always been at the center of that evolution. But if we are in constant transition, what does the term “nutrition transition” really define? 
Arguably, the concept of transition in the study of human populations was first introduced by Omran in 1971, in an article entitled “The Epidemiologic Transition” (Omran, 1971). In that paper, the author attempted to offer a systematic process by which to identify and characterize change, and in doing so, to be able to predict future trends. Another concept of transition often seen in the literature is the demographic transition – the shift from a pattern of high fertility and high mortality to one of low fertility and low mortality, typical of modern industrialized countries. Interpretations of the demographic and epidemiologic transition share a focus with the nutrition transition on the ways in which populations move from one pattern to the next. This concept of transition may also be applied to the study of changes in the food–diet environment and its impact on health.  The concept of nutrition transition, however, goes beyond diet, recognizing that most of the health effects of diets in human populations are also strongly affected by lifestyle, particularly physical activity. We therefore use the term nutrition transition to encompass these shifts not only in diet but also in physical activity and their effects on body composition. In other words, we must explicitly recognize the role of the other non-nutritional factors closely related to the health out-comes of interest.
 Why does the current nutrition transition merit special attention, and define a specific area of research in nutrition science? First, our ability to identify different patterns of intake in populations and to correlate these with health indicators has advanced sub-stantially over the past decades. Thus, the necessary data have reached a critical mass from which study can progress and inferences can be made. Second, the rate of change is such that its effects can frequently be identified in the population within a generation or two, facilitating their identification and quantification. Third, many of the changes in the area of nutrition and health are closely connected to economic and political changes, thus linking the nutrition transition with key determinants of the historical evolution of countries and regions.
This article focuses on the developing world. Our interest centers on the rapid shifts from a stage often termed the period of receding famine to one dominated by nutrition-related no communicable diseases (NR-NCD).
The most dramatic impact of the changes in food supply, dietary intake and lifestyle can be observed in the developing world. There are several reasons for this. First, the projected growth in world population for the next 30 years will occur almost exclusively in the developing world. Even more importantly, most of that population growth will occur in urban areas, where, as will be shown, the impact of the nutrition transition is most evident. Second, the health consequences of the nutrition transition, a continuing increase in the prevalence of NR-NCD, is having and will continue to have a dramatic impact in countries that, for the most part, have not yet solved the burden of nutritional deficiencies.
Traditionally, the diets of poor countries have been considered insufficient in quantity, and inadequate in quality. One reason for this has been the predominance of higher fiber, lower fat plant sources, which are known to be limited in certain essential nutrients, to have poor bioavailability for essential nutrients, and a low energy density. Paradoxically, the hunter–gatherer and the subsequent diet of countries in phase of receding famine, which are both low in fat and rich in fiber, are today considered the desired pattern for disease prevention in higher income industrialized countries. However, the diet of developing countries also has natural contaminants (goitrogenic substances, natural toxins, pesticides, microbial agents) that are undesirable.
What fuels the rapid shift in the stage of the nutrition transition? Critical elements include urbanization, internationalization (globalization) of food production and marketing, expansion of mass media and communications, and changes in the work market with predominance of low-energy output labor. Almost 90% of the projected world population growth over the next 20 years will take place in the developing world. Even more striking is the fact that almost all this growth will occur in urban areas. Thus, today’s developing world, still largely defined by the rural poor, will change dramatically in the next two decades, with the progressive dominance of an urban population. Urban dwelling is associated with an array of behaviors and lifestyles that are associated with higher levels of obesity and other NR-NCD. Globalization is a term that generates strong reactions, in spite (or perhaps because) of its vague definition. Included in what we term globalization is a shift in dominance on the economic, technological, cultural, and consumption level of goods that are mass produced by modern techniques and a system that is market driven. Although the term usually applies to recent trends in international trade, globalization has been an essential element for the continuing expansion of market economies since the industrial revolution. For example, by 1840, after the consolidation of the industrial revolution in England, 530 million yards of British cottons were exported to the “underdeveloped” regions of the world, compared to only 200 million for all of Europe (Hobsbawm, 1996). Thus, economic expansion of industrialized countries has historically depended on expansion of markets into the developing world. Market expansion is achieved by selling goods to increasing numbers of people, and also by creating new needs. Culture plays a key role in fulfilling this task; linking products to lifestyles, celebrities, and movies is one of the most effective means of increasing sales of nonessential products. The importance of culture for trade is such that the opinion-shaping industry (ad agencies, entertainment, and media) is one of the leading exports of the US and other developed countries. Television is one of the major purveyors of this cultural context, and it is not surprising that TV ownership and watching are increasing at high pace throughout the developing world (cf. the China case study). Television has a double impact on NR-NCD: as a vehicle for dissemination of unhealthy eating habits, and by promoting physical inactivity. Globalization of food production affects the nutrition transition in a number of ways. Use of modern technologies for mass production reduces the price of selected food items and worldwide distribution and marketing facilitate the introduction of processed foods to a wide range of countries. In turn, driven by the population growth mentioned above, a large proportion of global food production will be driven by the demands of developing countries. A recent study concluded that over the next 20 years, 85% of the increase in the demand for cereals and meat will come from developing countries (Pinstrup-Andersen et al., 1999). Because the food share of the household budget is substantially higher in developing than in developed countries (55% vs. 16% in 1997), changes in food prices and income tend to have a much stronger impact on people’s dietary intake in developing than in developed countries. This effect is reinforced by the stronger price elasticity associated with lower than with higher incomes. Thus, technological advances and aggressive marketing strategies that reduce prices of certain food items in developing markets result in increased consumption. A clear example of this is the increase in consumption of vegetable oils in the developing world (Drewnowski and Popkin, 1997).
Benjamin Caballero and Barry M. Popkin
Source; http://www.academicpress.com


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