A new study of 43 countries in Global Public Health, published online November 27, found that adult type-2 diabetes is 20 percent higher in countries that consume large quantities of high fructose corn syrup. "The study adds to a growing body of scientific literature that indicates HFCS consumption may result in negative health consequences distinct from and more deleterious than natural sugar," Michael Goran, of the University of Southern California Department of Preventive Medicine and co-author of the new study, said in a prepared statement.
Countries in which per person annual high fructose corn syrup (HFCS) consumption was less than 0.5 kg had similar BMIs, daily calorie intake and total sugar intake as did countries in which HFCS was higher. The big difference in these two groups of countries was diabetes prevalence.
The link between HFCS and poor health outcomes—such as obesity or diabetes–has often been speculated, but it has been difficult to prove. The availability of the cheaper-than-sugar sweeteners starting in the U.S. in the 1970s appears to have helped boost the number of overall calories people imbibe. In the U.S. today, for example, high fructose corn syrup is in everything from sodas to ketchup. In fact, we each consume, on average, some 24.8 kilograms of this processed corn sweetener every year. With the extra calories, weight gain has quickened, leading to more obesity, one of the strongest risk factors for type-2 diabetes.
HFCS may also pose a greater risk for diabetes greater than pure sugar alone. Instead of a composition evenly divided between fructose and glucose like table sugar, HFCS contains as much as 30 percent more fructose. (The exact quantities are unknown because manufacturers are not required to disclose the amount on food and beverage packages.) Glucose is metabolized quickly and used as energy or retained as fat. But fructose processing is more complex. It is broken down primarily in the liver and seems to induce less leptin production (a hormone that signals fullness to the body) and less insulin (which is why sweeteners composed primarily of fructose are sometimes recommended for people who already have diabetes). Some studies have also found fructose consumption increases the types of fats that are linked to insulin resistance, a hallmark of diabetes. These scattered findings suggest that "our metabolism has not evolved sufficiently to be able to process the fructose from high fructose corn syrup in the quantities that some people are consuming it," Stanly Ulijaszek, of the University of Oxford and study co-author, said in a prepared statement.
Some illuminating international differences emerged during the course of the study. For example, the European Union imposes production quotas for HFCS for member countries. Those countries, such as Sweden, that do not use the sweetener in their own food supply can export it to countries, such as Hungary, that are willing to buy more for residents. This distribution imbalance allowed the researchers to compare countries that were similar in other respects (BMI, gross national product, etc.) but different in HFCS consumption.
While the U.S. is the largest producer—and consumer—of HFCS and has been for decades (thanks in large part to farm subsidies), other countries are just beginning to experience high amounts of HFCS in the food system. Mexico, for example, long limited imports of HFCS to protect their own sugar market. In 2008, however, those barriers were removed, and for the past few years, HFCS has been flooding in from the U.S. The authors of the study argue that with the new findings, perhaps some of these policies should be revisited.
Further research into the mechanisms for the possible link between HFCS consumption and diabetes risk remains to be done. But, "if HFCS is a risk factor for diabetes—one of the world's most serious chronic diseases—then we need to rewrite national dietary guidelines and review agricultural trade policies," Tim Lobstein, director of policy at the International Association for the Study of Obesity, said in a prepared statement.