High-fructose corn syrup (HFCS), a cheap sweetener that has been a popular food additive in recent decades, has often been fingered as a driver of the obesity epidemic. Grocery store aisles are awash in foods and beverages that contain HFCS and it is common in sodas as well as in everything from ketchup to snack bars.
These fears may be well founded, according to a new study, albeit in only 20 volunteers. Here’s how fructose, one of the two components of high-fructose corn syrup (the other one is glucose), might be stimulating appetite:
Fructose, a new Yale University School of Medicine study published January 1 in the prestigious Journal of the American Medical Asssociation finds, has a marked affect on the brain region that regulates appetite, suggesting that corn syrup and other forms of fructose might encourage over-eating to a greater degree than glucose. Table sugar has both fructose and glucose, but high-fructose corn syrup, as the name suggests, contains a higher proportion of fructose.
To test how fructose affects the brain, researchers studied 20 healthy adult volunteers. While the test subjects consumed sweetened beverages, the researchers used fMRIs (functional magnetic resonance imaging) to measure the response of the hypothalamus, which helps regulate many hunger-related signals, as well as reward and motivation processing.
Volunteers received a 300-milliliter cherry-flavored drink sweetened with 75 grams (equivalent to about 300 calories) of fructose as well as the same drink sweetened with the same amount of glucose. These different drinks were given, in random order, at sessions one to eight months apart. The researchers also took blood samples at various time points and asked volunteers to rate their feelings of hunger and fullness.
Of course, this study went to extremes serving either pure glucose or fructose — The most widely used varieties of high-fructose corn syrup are: HFCS 55 (mostly used in soft drinks), approximately 55% fructose and 42% glucose; and HFCS 42 (used in beverages, processed foods, cereals and baked goods), approximately 42% fructose and 53% glucose. So neither serves up 100% fructose.
Fructose and glucose look similar molecularly, but fructose is metabolized differently by the body and prompts the body to secrete less insulin than does glucose (insulin plays a role in telling the body to feel full and in dulling the reward the body gets from food). Fructose also fails to reduce the amount of circulating ghrelin (a hunger-signaling hormone) as much as glucose does. (Animal studies have shown that fructose can, indeed, cross the blood-brain barrier and be metabolized in the hypothalamus.) Previous studies have shown that this effect was pronounced in animal models.
So, could fructose consumption alone really be playing such an outsized role in expanding our pant sizes?
“A common counterargument is that it is the excess calories that are important, not the food. Simply put: just eat less,” the study’s authors noted. “The reality, however, is that hunger and fullness are major determinants of how much humans eat, just as thirst determines how much humans drink. These sensations cannot simply be willed away or ignored.” In order to eat less (and consume fewer calories overall), they argued, then, one should avoid foods or ingredients that fail to satisfy hunger. And that, according to the results from the new study, would mean those fructose-sweetened foods–and drinks.
Interesting. What do you think? Leave your thoughts in the comments!
Click here for the full article »