Wander the aisles of any grocery store and you are likely to find plenty of products that contain high-fructose corn syrup. The controversial ingredient has been added to everything from ketchup to crackers to bread and more—but what exactly is it, and do you need to avoid it?
High-Fructose Corn Syrup
High-fructose corn syrup is a cheap sweetener, which has made it an increasingly popular additive as companies look for ways to cut costs and sweeten products. It is produced by milling corn to produce cornstarch, processing that starch to yield corn syrup, and then adding enzymes to convert some of the glucose into fructose. The resulting syrup is known as HFCS42 because it contains approximately 42 percent fructose. The syrup can then be altered to HFCS90, however, which contains 90 percent fructose.
Fructose versus Glucose
As the name implies, high-fructose corn syrup has a high proportion of fructose. In contrast, regular table sugar has a balance of glucose and fructose, which are bound together as sucrose. Although fructose and glucose are similar, fructose is metabolized differently and prompts the body to secrete less insulin than does glucose. What’s more, glucose does a better job of reducing the amount of ghrelin—a hunger-signaling hormone—than does fructose. This means that fructose might encourage overeating compared with glucose.
Fructose and the Brain
As fructose consumption has increased, the population has grown more obese— and researchers have begun to suspect a correlation. To study this link, researchers from Yale University studied 20 healthy adult volunteers who consumed sweetened beverages while undergoing functional magnetic resonance imaging (fMRI ).
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The volunteers received two different drinks in random order at sessions one to eight months apart. Each drink was a 300 mL cherry-flavored drink, but one was sweetened with 75 grams (g) of fructose and the other was sweetened with 75 g of glucose.
Researchers used the fMRI to measure the response of the hypothalamus, which helps regulate many hungerrelated signals as well as reward and motivation processing. They also took blood samples at various times and asked volunteers to rate their feelings of hunger and fullness.
The results showed a substantial difference in hypothalamic activity after consuming the fructose-sweetened beverage compared with the glucosesweetened beverage. This activity was evident within 15 minutes of consuming the drink. Glucose reduced hypothalamic activity, whereas fructose appeared to trigger a small spike in this area. What’s more, the glucose drink increased feelings of fullness, leading the researchers to speculate that participants would be less likely to consume more calories after having something sweetened with glucose than something sweetened with fructose.
The Not-So-Sweet Truth
This small study adds to the growing body of research linking high-fructose corn syrup to obesity and possibly even insulin resistance. These researchers concluded that high-fructose corn syrup might be encouraging overeating and, as a result, leading to weight gain. If high-fructose corn syrup is indeed affecting the brain region that regulates appetite and thus failing to promote satiety, the sage advice to simply eat fewer calories is of no use here. Better advice is to avoid foods that fail to satisfy hunger. In other words, it might be time to become an expert label reader and take foods containing high-fructose corn syrup off the menu.
Page KA , Chan O, Arora J, et al. Effects of fructose vs glucose on regional cerebral blood flow in brain regions involved with appetite and reward pathways. Journal of the American Medical Association. 2013;309(1):63-70. doi: 10.1001/jama.2012.116975.