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Animal study suggests existence of sugar addiction, says scientist

By Caroline Scott-Thomas , 11-Dec-2008

Researchers at Princeton University claim that they have laid down the final pieces of evidence necessary to prove the existence of sugar addiction in animal studies.

Professor Bart Hoebel, who led the study, is due to present the research today at the American College of Neuropsychopharmacology in Scottsdale, Arizona. The presentation follows a decade of research into sugar addiction, culminating in this latest rat study, which Hoebel claims could provide insight into the nature of addiction and eating disorders, such as bulimia.

Until now, Hoebel’s study had shown two out of three elements of addiction: increased intake, and signs of withdrawal. Hoebel claims that his current research completes the recognised addiction model by showing the existence of craving and relapse associated with sugar, and its underlying mechanism.

“If bingeing on sugar is really a form of addiction, there should be long-lasting effects in the brains of sugar addicts,” Hoebel said. “Craving and relapse are critical components of addiction, and we have been able to demonstrate these behaviours in sugar-bingeing rats in a number of ways.”

The researchers conducted the study by restricting the rats’ food while they slept and for four hours after waking, and then providing a ten per cent sugar solution – alongside their chow – on which they would subsequently binge.

Altered brain function

After one month of the high sugar diet, the researchers observed that the rats’ brains had adapted to the higher levels of dopamine released as a result, and had a reduced number of dopamine receptors. Meanwhile, the number of opioid receptors had increased.

After a period of withdrawal, however, the researchers found that the rats were willing to work harder in order to get to the sugar solution and consumption levels went up.

Hoebel said: “In certain models, sugar-bingeing causes long-lasting effects in the brain and increases the inclination to take other drugs of abuse, such as alcohol.”

The researchers also claim that these changes in the rats’ brain function explain the adoption of other destructive behavioural patterns during periods of sugar withdrawal, such as increased alcohol consumption and hypersensitivity to amphetamines.

“After receiving a dose of amphetamine normally so minimal it has no effect, they became significantly hyperactive. The increased sensitivity to the psychostimulant is a long-lasting brain effect that can be a component of addiction.” Hoebel said.

Previous studies into sugar addiction have been inconclusive. Nevertheless, the food industry is already in the midst of major reformulation of products to meet targets for reduced sugar, as well as salt and fat content.

“Our work provides links between the traditionally defined substance-use disorders, such as drug addiction, and the development of abnormal desires for natural substances,” Hoebel said. “This knowledge might help us to devise new ways of diagnosing and treating addictions in people.”

Hoebel stressed that while the research is exciting, more work needs to be done to understand its implications for treating people.

The Sugar Bureau, which monitors and conducts research into sugar and nutrition, was contacted for comment, but could not be reached prior to publication.

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