Researchers examine how the brain and body respond to glucose and fructose

Glucose vs. fructose

In this study, researchers focused on how the brain and body respond to two types of sugar—glucose and fructose.

Glucose, which is found in nearly all carbohydrate-containing foods, such as bread and fruit, fuels all of the cells in the human body, including the brain.

Fructose is a simple sugar found in fruits and vegetables that is mainly metabolized in the liver. Foods with high levels of fructose include most soft drinks, honey and many salad dressings. Although tasty, foods with lots of fructose are often unhealthy.

The research is based on 24 healthy young men and women who came in for brain scans in the mid-morning before they ate breakfast. On one occasion, they consumed a drink sweetened with fructose; on another day, they consumed a drink sweetened with glucose.

Researchers sampled blood for hormones that help control appetite and performed brain scans while the volunteers looked at pictures of tasty foods (like pizza) or objects (like a lamp) and rated their hunger and desire for food.

"This allowed us to see how consuming fructose compared to how glucose affected brain, hormone and hunger responses," Page explained.

The results suggest that consuming fructose relative to glucose activates brain reward regions and may promote feeding behavior.

When study participants consumed fructose compared to glucose, it led to greater activity in brain reward areas, greater ratings of hunger and more desire for food. This tendency played out the same even when participants were offered a monetary incentive not to indulge their sweet tooth.

"We gave the volunteers choices between being served tasty food immediately after the study or having money sent to them one month later," Page explained.

"When the study participants consumed fructose, they had a greater willingness to give up the money to obtain immediate high-calorie foods, compared to when they consumed glucose."