Sugar Addiction

[Guest guest]

Monday June 18 2:17 PM ET

Rat Studies Show Evidence of 'Sugar Dependence'

By E. J. Mundell

TORONTO (Reuters Health) - Could many of us be slaves to our sweet tooth?

New research in rats suggests that the brain can become dependent, if not

outright addicted, to sugars in food.

``The brain has opioid compounds and they seem to be released by palatable

tastes such as sugar, fat, ice cream, cake,'' explained Dr. Bart Hoebel, a

researcher at Princeton University specializing in the neuroscience of

addiction. He presented his findings Saturday at the annual meeting of the

American Psychological Society.

Numerous studies have shown that the activity of the nucleus accumbens, an

area in the forefront of the brain, is key to the ``high'' sought by

abusers of cocaine, amphetamines, nicotine and other addictive substances.

Drug intake stimulates receptors in the nucleus accumbens to release high

levels of opioids as well as dopamine, the neurochemical thought to be a

driving force behind drug-seeking behavior.

Because the nucleus accumbens is also involved in regulating normal

feeding, Hoebel's team theorized that food might induce similar behavioral

responses.

In their investigation, researchers fed rats a sugary solution for 12-hour

periods over a number of weeks, then either abruptly cut off the rodents'

supply of the sweet treat or gave them a drug that blocked the brain's

opioid receptors.

The result? Compared with rats fed regular chow, sugar-fed rats developed

``mild'' symptoms indicative of withdrawal, such as teeth-chattering, an

increased frequency of high-pitched crying and anxiety. And when

researchers allowed these rats renewed access to sugar they

``binged''--consuming up to 30% of their daily sugar intake within the

first hour of re-introduction.

Subsequent laboratory investigation of the brains of sugar-fed rats showed

an accelerated growth of dopamine receptors in the nucleus accumbens,

indicative of a growing dependence on sugar.

The behavior of the rats in the study is similar to patterns seen in drug

abuse and withdrawal. Bingeing, especially, ``is very important,'' Hoebel

noted. ``If you take in a lot of food at once you're going to get a lot of

dopamine and opioids all at once--that's a little like getting a small shot

of amphetamine and morphine.''

Taste, rather than calories, seems to trigger this neuro-behavorial

process. Rats fed saccharin displayed similar dependent behaviors to those

fed sugars, even though saccharine contains no calories. ``The evidence so

far is that if it tastes good, it should work,'' he said, although he

speculates that the addition of calories may enhance the effect.

Hoebel stressed that, right now, ``we haven't shown sugar addiction, but

for the experts who define these words, we have shown sugar dependence.''

In dependence, individuals still maintain some control over their cravings

for a particular substance, but they lose this control when dependence

turns into addiction. Genetics could play a strong role in the process,

Hoebel said, leading some individuals to be more prone than others to what

he called ``food abuse.''

Future studies in humans are planned to assess whether an actual addiction

to foods could help drive eating disorders such as binge eating or bulimia,

where individuals lose that vital sense of control. ``We've seen that drugs

of abuse act, in part, via the feeding system,'' Hoebel said, ``and many

scientists have gone to great lengths to show that that system is involved

in addiction. Therefore, maybe food itself could be addictive. Maybe this

is a system that evolved to be addictive.''