A health-food supplement has shown promise as a way to help pathological gamblers break the habit, University of Minnesota researchers said Wednesday.

“We were able to reduce people’s urges to gamble,” chief researcher Dr. Jon Grant said about the small study on the amino acid N-acetyl cysteine (NAC), sold in some health-food stores as an immune-system booster and aid to reducing toxins.

The researchers ran an eight-week trial on 27 people, who were given increasing doses of the amino acid. "At the end of the trial, 60 per cent of the participants reported fewer urges to gamble," they said in a release.

The trial then continued with 13 of the original 16 people who responded to NAC entering a double-blind study, where neither the researcher nor the subjects knew which subjects were getting NAC, and which were getting a placebo.

"About 83 per cent who received the supplement continued to report fewer urges to gamble. Nearly 72 per cent of those who took the placebo went back to gambling," the researchers said.

NAC increases the level of glutamate, a neurotransmitter that conveys signals to brain cells.

The study is the first to examine the efficacy of a glutamate-modulating agent in the treatment of pathological gamblers, Grant said.

"The efficacy of NAC lends support to the hypothesis that pharmacological manipulation of the glutamate system might target core symptoms of reward-seeking addictive behaviours such as gambling," said an abstract of the study, published in the Sept. 15 issue of Biological Psychiatry.

NAC has been tested to curb drug addictions among animals, and Grant is currently investigating whether it could help methamphetamine users quit.

The researchers are seeking additional money to conduct a larger experiment.