Research shows that consuming too much sugar over time contributes to weight gain and obesity-related conditions such as Type 2 diabetes and cardiovascular diseases. So why do we keep going back for more, even when the risks are clear?
In a unique experiment, Dr. Kyle S. Burger, assistant professor of nutrition at the UNC Gillings School of Global Public Health and director of UNC’s Neuropsychology of Ingestive Behavior Laboratory, examined the behavioral responses of 20 healthy-weight individuals to a sugar-sweetened beverage and beverage logos after the individuals had a daily drink of that beverage for three weeks.
[Photo: UNC’s Dr. Kyle Burger found that daily consumption of a high-sugar juice beverage altered brain responses while subjects drank the beverage and looked at its logo – and produced behavioral responses when seeing the logo alone. Photo by Uzalgaijin.]
Dr. Burger’s research, published online Feb. 8 in the American Journal of Clinical Nutrition, found that daily consumption of a high-sugar juice beverage altered brain responses while subjects drank the beverage and looked at its logo – and produced behavioral responses when seeing the logo alone.
Such patterns of brain and behavioral responses are typical in people with food or substance abuse, and nutrition researchers have hypothesized that the responses themselves may cause an escalation in intake of food or substances.
“This is the first study to demonstrate experimentally the potentially negative and previously undetected consequences of daily sugar-sweetened beverage consumption,” said Dr. Burger. “The degree to which daily consumption of sugary beverages in this study altered brain and behavioral patterns – before affecting typical health markers associated with high sugar consumption (such as weight gain) – is concerning. Understanding these effects is critical, given that most Americans consume sugary beverages every day and that the brain response patterns that emerged here have been hypothesized to support future intake.”
The randomized controlled trial, which used functional magnetic resonance imaging (fMRI), revealed the extent to which regions of the brain (e.g., the striatum, prefrontal cortex, parietal lobe) responded to tastes of a high-sugar beverages and images of the beverages’ logos.
Brain and behavioral responses to the branded, high-sugar beverages were measured before and after 21 days of daily consumption of the beverage and exposure to the logos. Participants visited Dr. Burger’s lab every other weekday during the period to drink the beverage, be weighed and pick up the following day’s beverage.
Interestingly, no weight change occurred during the study period. The daily consumption caused a decrease in the striatum response (a region associated with motivated behavior and reward) when drinking the sugary beverage. Participants also showed a decrease in prefrontal brain response (a brain region associated with cognitive control) when they saw the logo for the beverage. This decreased prefrontal response was related to the speed with which participants responded to the drink’s logo.
Lastly, participants showed increases in a brain region associated with processing emotionally salient stimuli (parietal lobe) when viewing all beverage logos, indicating that consumption of one sugary beverage for 21 days may make similar drinks more noticeable to participants. Together, these findings suggest that daily consumption of a sugary beverage established a decision-making bias toward the consumed beverage and perhaps increased awareness to similar beverages.
“Numerous researchers have indicated that sugar has an ‘addictive-like potential,’” Dr. Burger said, “but no group has studied how the human brain changes as a person begins to regularly drink a highly palatable, high-sugar beverage. The implication that individuals who regularly consume high-sugar beverages unknowingly alter brain-level processing of beverage stimuli is worth further investigation, especially considering the debate over policies intended to limit sugar-sweetened beverages, such as the soda tax and portion limits.”
The study was supported by a National Institutes of Health research grant to the UNC Nutrition Obesity Research Center.