People with a sweet tooth may be at risk of developing alcoholism, a new study suggests.
The research using functional magnetic resonance imaging (fMRI) has found that recent drinking is related to the orbitofrontal-region brain response to an intensely sweet stimulus, a brain response that may serve as an important phenotype, or observable characteristic, of alcoholism risk.
"It has long-been known that animals bred to prefer alcohol also drink considerably greater quantities of sweetened water than do animals without this selective breeding for alcohol preference," said David A Kareken from Indiana University School of Medicine.
"More recently, it has become clear that animals bred to prefer the artificial sweetener, saccharin, also drink more alcohol. Although the data in humans are somewhat more variable, some studies do show that alcoholics, or even non-alcoholics with a family history of alcoholism, have a preference for unusually sweet tastes.
"Thus, while the precise reasons remain unclear, there does seem to be significant evidence suggesting some link between the rewarding properties of both sweet tastes and alcohol," said Kareken.
Kareken added that this is the first study to examine the extent to which regions of the brain's reward system, as they respond to an intensely sweet taste, are related to human drinking patterns.
Kareken and his colleagues recruited 16 (12 males, 4 females) right-handed, non-treatment seeking, healthy volunteers with a mean age of 26 years from the community.
All participants underwent a taste test using a range of sucrose concentrations, and their blood oxygen dependent (BOLD) activation was measured during an fMRI scan while receiving small squirts of either water or an intensely sweet mixture of sugar in water. All were asked about their drinking patterns.
"Our study was designed to determine which brain areas responded to sweet taste - as compared to plain water - and the extent to which these brain responses were related to subjects' binge-drinking patterns, the number of alcoholic drinks subjects consumed per day when drinking," said Kareken.
What the researchers found was that the response to this intensely sweet taste in the left orbitofrontal area correlated significantly with subjects' drinking patterns.
"Specifically, the trend was such that those who drank more alcohol on drinking days had stronger left orbitofrontal responses to the intensely sweet water," said Kareken.
"Subjects' subjectively rated liking of the sweetened water also contributed to this relationship, so that both the brain response itself, as well as liking of the sugared water, collectively correlated with drinking behaviour," he said.
The findings will appear in the journal Alcoholism: Clinical & Experimental Research.
