Glucose and fructose are both simple sugars–and equal parts of each is the recipe for table sugar. High-fructose corn syrup is a bit more intensely sweet because it’s made up of 55% fructose. But scientists have long suspected there are differences in the way the human body processes these two forms of carbohydrate. A study published in the March 2011 issue of the journal Diabetes, Obesity and Metabolism raises more questions than it answers.
Researchers at Oregon Health and Science University scanned the brains of nine healthy, normal-weight subjects in the minutes after each got an infusion of equal volumes of glucose, of fructose and of saline. The brain scans aimed to capture activity in a relatively small swath of the human brain in and around the hypothalamus, which plays a key but complex role in setting appetite levels and directing production of metabolic hormones.
The researchers found that “cortical control areas”–broad swaths of gray matter that surrounded the hypothalamus — responded quite differently to the infusion of fructose than they did to glucose. Across the limited regions of the brain they scanned, Purnell and his colleagues saw that glucose significantly raised the level of neural activity for about 20 minutes following the infusion. Fructose had the opposite effect, causing activity in the same areas to drop and stay low for 20 minutes after the infusion. Saline–the control condition in this trial–had no effect either way.
What does a different response in “cortical control areas” mean? Within some of the “cortical control areas” where differences were seen, lie some important neural real estate, including regions where notions of reward and addiction are processed. As scientists have a closer look in future studies, they should be able to zero in on which specific areas are affected differently by the two forms of sugar.