The link between economic growth and the worldwide diabetes epidemic, explained
As globalization exports our culture across the world, it also spreads our health problems. For much of the 20th century, a person's likelihood to develop type-2 diabetes depended as much on the wealth of their nation as their biology. Those living in the developed world survived to old age and eventually succumbed to "diseases of affluence": cancer, cardiovascular disease, and diabetes. In contrast, undernourishment, violence, and communicable diseases ravaged the health of residents of developing countries.
And this is the way things remain in the developed world: even in poor parts of the United States, almost no one dies of tuberculosis. But in low- and middle-income countries, the distinction fades. The "diseases of affluence" have embedded themselves in communities anything but affluent. Now, cholera strikes next door to cancer; the malnourished and diabetic share a roof.
In this new landscape of health in the developing world, the impact of diabetes is momentous. Since 1980, the number of diabetics worldwide has ballooned from 152 million to between 285 and 347 million today. Of these, three-quarters live in the developing world, where diabetes afflicts more than six times as many people as HIV. Why, if infectious diseases persist and life expectancies remain low, has diabetes taken such a toll on the health of the impoverished?
One explanation relies on a trio of social forces: aging population, urbanization, and economic growth. According to this model, as people move to cities, they give up manual labor and adopt a more sedentary lifestyle. This, combined with longer lives and increases in income that allow people to buy more food, may drive the increasing rate of obesity around the world. While obesity and diabetes remain distinct problems -- not all obese people develop diabetes and not all diabetics have weight problems -- they so closely interrelate that researchers frequently lump them together.
Yet, models based on these social factors have significantly underestimated the spread of diabetes in the developing world over the past 20 years. A group of researchers affiliated with the London School of Hygiene and Tropical Medicine and the World Health Organization set out to explain this gap. Their findings, published in the journal Public Health Nutrition, compares 173 countries' diabetes prevalence, food consumption and socioeconomic situations.
As expected, increased urbanization, economic development, sedentary lifestyle, and total food available corresponded to higher rates of diabetes. However, after adjusting this data to control for differences in refined sugar consumption, these correlations disappeared. This suggests that rather than an inherent connection between urbanization and diabetes, for instance, the correlation between the two appears because life in cities exposes people to more sugar. A growing body of public health research on high-income countries supports this conclusion that eating more processed foods high in sugar increases the risk of diabetes. Additionally, research on refined sugars indicates that their metabolism in our bodies may cause changes in insulin response that contribute to diabetes regardless of obesity. The populations examined in this study mirror this physiological phenomenon: after adjusting for obesity, the correlation between sugar and diabetes remains. Amidst the complex solutions offered, it appears that expanded consumption of sugar propels the pandemic of diabetes.
While affluence and urbanization may not cause diabetes, economics dictate a country's exposure to refined sugars and processed foods. In this 47-year study, GDP increases in low- and middle-income countries were positively correlated with the amount of sugar available to the average person. At first glance, it appears that with more money people began to buy processed foods they could not afford before. But it's really a byproduct of economic growth that may be responsible for increasingly sugary diets. According to the data, the growing share of an average person's diet from sugar was tied not to GDP, but to increases in food imports. Dr. Sanjay Basu, lead author of the study, explains that the opening of international trade markets that comes with economic growth allows for the influx of cheap, processed foods. Soda and sweets from abroad offer cheap replacements for a traditional diet and put the populace at risk for diabetes.
Still, it's worth remembering that correlative studies only suggest trends and relationships between diabetes and diet, and population data cannot prove with scientific accuracy that sugar causes diabetes.