Chocolate stouts, sugary shots, hard ciders. Bars and breweries have been combining alcohol with sweets for a long time. Now, research has shown that these libations might have inadvertently tapped into an underlying neural connection, as the brain’s response to highly sweet tastes may be linked to its response to drinking alcohol, according to a study published online ahead of print in Alcoholism: Clinical & Experimental Research.
Specifically, fMRI results have shown the amount a person drinks is connected to sweet stimulus response in the ventral striatum, amygdala and parts of the orbitofrontal cortex—regions that are part of the brain’s reward system.
David A. Kareken, PhD, of Indiana University School of Medicine in Indianapolis, and colleagues, based their findings on a study of 16 healthy volunteers, mean age of 26, who had their blood oxygen level-dependent (BOLD) activation measured by fMRI while tasting small squirts of either plain water or an intensely sweet mixture of sugar and water. Participants were asked to subjectively rate the taste, as well as provide details about their drinking patterns.
The sugar water provoked significant BOLD activation in the primary gustatory cortex, amygdala, right ventral striatum and bilateral orbitofrontal cortex, with the level of activation being significantly correlated to the subjects’ self-reported drinking patterns, according to the authors. “Thus, the stronger the response in this region, the greater the density of subjects’ reported daily drinking.”
Consideration of the test subjects’ subjective preference for the taste of the sugar water further accounted for variance in the number of drinks per drinking day beyond brain activation alone, added Kareken and colleagues.
One possible explanation for the phenomenon is “reward deficiency” syndrome, explained the authors. In certain cases, a greater degree of stimulation is needed to elicit a normal response in the brain, which can create issues with drugs of abuse. “A preference for an intensely sweet taste could be also consistent with an intrinsic need for a greater than average degree of hedonic stimulation.”
However, Kareken and colleagues noted that not all previous research is consistent with the reward deficiency hypothesis in the case of alcoholism.
The study was the first to examine the extent to which specific regions of the brain’s reward system respond to sweet stimulus, according to the researchers. Prior studies had suggested a link between a preference for alcohol and sweets in general among both animals and humans.