Twin Study Suggests Genetic Link Between Craving Alcohol, Sweets

"Several years ago, we found the first clinical evidence linking sweet liking with alcoholism in a study that involved subjects tasting a wide range of concentrations of table sugar in water,"said Dr. David H. Overstreet, associate professor of psychiatry at the UNC-CH School of Medicine and a member of Skipper Bowles Center for Alcohol Studies. "In this new study, we found that despite different life experiences, twin brothers continue to share sweet and alcohol preferences."

Twins also may share similar emotional responses to eating sweets, Overstreet said. To researchers' questions they offered similar responses like "having something sweet to eat makes me feel happier," and "I am less irritable if I have something sweet to eat."

Preliminary results of the continuing research, which included 19 pairs of twins, are being presented Monday (Nov. 6) at a Society for Neuroscience meeting in New Orleans.

"The twin study also allowed us to collect additional information about the association between different characteristics of sweet liking and alcohol intake in non-alcoholic subjects since none of our twins were alcoholics," Overstreet said.

"For example, those individuals who reported drinking more alcohol on occasion and having more alcohol-related problems also had problems with controlling how many sweets they ate," he said. "They were more likely to report urges to eat sweets and craving for them. They also were more likely to report this craving when they were nervous or depressed, and they believed eating sweets made them feel better."

Other investigators were Drs. Alexey B. Kampov-Polevoy, formerly of UNC-CH and now with the Mt. Sinai School of Medicine in New York; James C. Garbutt, associate professor of psychiatry at UNC-CH; and Lenn Murrelle and Lindon Eaves, both of the Medical College of Virginia.

The new UNC-CH study extends earlier work in rodents showing that preference for sweeter solutions reliably predicts the propensity to consume alcohol. It also extends the first published human research of its kind in which UNC-CH scientists asked 20 abstinent alcoholic men and 37 non-alcoholic men to taste five sugar solutions. The solutions ranged from not sweet at all to very sweet, with the strongest being more than twice as sweet as the soft drink Coca-Cola Classic.

Sixty-five percent of alcoholics preferred the sweetest solution compared to only 16 percent of non-alcoholics. All subjects could distinguish among the different concentrations.

"Sweet liking is a basic pleasurable reaction that may be seen in humans and other mammals within minutes after birth," Kampov-Polevoy said. "Disturbance in pleasurable response to sweets may reflect a dysfunction in the brain's system of positive reinforcement, which is also involved in development of alcoholism."

The Bowles center team has been exploring the relationship between liking stronger sweets and alcohol craving for more than a decade.

"Our findings are interesting given the advice found in the early writings of Alcoholics Anonymous that eating and drinking sweets allays the urge to drink," said Kampov-Polevoy, a physician instrumental in bringing the AA program to the former Soviet Union in the late 1980s. The researchers hope to design a test to predict who is at greatest risk of developing alcoholism.

"Perhaps a benign and inexpensive sweet test, which takes only 10 minutes to perform, may be a first step in developing such a test," he said. "This test could be used to screen youngsters to detect those with a predisposition to alcoholism, which might allow early education and prevention rather than waiting until alcoholism develops."

Obviously, most people like sweets and most will not become alcoholics, Kampov-Polevoy said. Alcoholics, however, like stronger concentrations, and such a test may help us better understand who might be at risk of alcohol dependence.

Further study of the effects of sweets on alcohol intake may help develop better treatments for alcoholism, such as special diets for recovering alcoholics, and in understanding the genetic risk for alcoholism in humans, Overstreet said. The latest finding suggests it may be possible to turn off alcohol craving with the help of sweets or by controlling the mechanisms that make both alcohol and sweets desirable to some people.