Princeton University researchers recently reported the results of two studies that showed rats eating high-fructose corn syrup gained more weight than those eating plain table sugar (sucrose). The two experiments, conducted by the Department of Psychology and the Princeton Neuroscience Institute, are important because their results help debunk what some experts believe – that there is no difference between sucrose and high-fructose corn syrup in terms of weight gain.
In the study of long-term consumption, the rats that were allowed access to HFCS in addition to their rat chow not only gained 48% more weight, but also developed higher triglyceride levels and more abdominal fat.
In the second study, rats supplemented their standard diet with water containing either sucrose or high-fructose corn syrup. The sugar concentration of the sucrose solution was equal to what is found in some commercial sodas, but the HFCS mixture was half as concentrated than that normally found in soft drinks. Once again, the rats fed the HFCS diet gained significantly more weight than those eating table sugar, even though they consumed the same number of calories.
What’s the difference between sucrose and high-fructose corn syrup?
As I mentioned in last week’s post about the health dangers of HFCS, table sugar is made up of 50% glucose and 50% fructose. HFCS, on the other hand, typically adjusts this fructose/glucose ratio several ways, ranging from 42% fructose to 90% fructose. Most of the soft drinks sold in the United States use HFCS that is comprised of 55% fructose¹, giving it five percent more fructose than is found in regular table sugar.
Hilary Parker of News at Princeton explains:
…[A]s a result of the manufacturing process for high-fructose corn syrup, the fructose molecules in the sweetener are free and unbound, ready for absorption and utilization. In contrast, every fructose molecule in sucrose that comes from cane sugar or beet sugar is bound to a corresponding glucose molecule and must go through an extra metabolic step before it can be utilized.
This creates a fascinating puzzle. The rats in the Princeton study became obese by drinking high-fructose corn syrup, but not by drinking sucrose. The critical differences in appetite, metabolism and gene expression that underlie this phenomenon are yet to be discovered, but may relate to the fact that excess fructose is being metabolized to produce fat, while glucose is largely being processed for energy or stored as a carbohydrate, called glycogen, in the liver and muscles. ²
Another possible explanation for the weight gain caused by HFCS comes from a Rutgers University Department of Food Science study reported at the 2007 American Chemical Society meeting. Dr. Chi-Tang Ho’s team found that one HFCS-containing soda had five times the reactive carbonyl compounds found in the blood of an adult with diabetes. Some scientists believe that carbonyls (which are found in higher amounts in diabetics) trigger cell and tissue damage that can result in diabetes.
For the study, Dr. Ho and team tested 11 different carbonated soft drinks containing HFCS and found these beverages contained “astonishingly high” levels of reactive carbonyls. Ho was cited as saying that these reactive carbonyls are associated with “unbound” glucose and fructose which are the sugar present in HFCS. By contrast, table sugar does not contain reactive carbonyls.³
High fructose corn syrup is in thousands of food products in the United States, from soft drinks to condiments to baked goods. Is it any wonder that we’re in the middle of an obesity epidemic?
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soda-riffic, by dcJohn on flickr
1) Not So Sweet: Missing Mercury and High Fructose Corn Syrup, by David Wallinga, M.D., Janelle Sorensen, Pooja Mottl, Brian Yablon, M.D. Institute for Agriculture and Trade Policy, Minneapolis, Minnesota, January 2009.
2) A sweet problem: Princeton researchers find that high-fructose corn syrup prompts considerably more weight gain, by Hilary Parker: Princeton University News, March 22, 2010.
3) Soft drinks with HFCS may be a risk factor for diabetes, by Sue Mueller, Aug 25, 2007: Foodconsumer.org