CHICAGO (AP) -- A small but promising study found that an over-the-counter dietary supplement may slow the progression of Parkinson's disease.

Existing treatments may ease symptoms of the degenerative brain disorder but are not believed to affect the underlying disease process. The new study found evidence that a naturally occurring compound called coenzyme Q-10, or CoQ10, may help stop the nerve cell death that characterizes Parkinson's.

"This is really sort of the Holy Grail of what we're trying to do in Parkinson's disease," said Dr. Tim Greenamyre, a Parkinson's scientist at Emory University who was not involved in the research. "They're on the right track."

The study involved just 80 people. Half ate maple-nut flavored wafers containing various CoQ10 doses, half took a placebo for up to 16 months.

By the study's end, the 23 patients on the highest daily doses had 44 percent less decline in mental function, movement and ability to perform daily living tasks than did the placebo group.

Lead author Dr. Clifford Shults of the University of California at San Diego and colleagues cautioned that there is not enough proof to recommend that Parkinson's patients use the supplements, which are sold over the counter as antioxidants that purportedly help improve heart function.

But the findings are "tremendously encouraging," Shults said. "We really need to do a definitive study" to confirm the findings.

The study appears in October's Archives of Neurology.

Parkinson's is a progressive disorder that results from degeneration of nerve cells that produce a neurotransmitter called dopamine, which is needed to control muscle activity.

Symptoms include tremors, stiffness and a shuffling gait. Standard treatment includes the drug levodopa, which is converted into dopamine in the brain.

Research has suggested that energy-supplying structures Ënside cells, called mitochondria, may be impaired in Parkinson's disease. CoQ10, a compound made in the body, is believed to help mitochondria function, and previous research by Shults and others found that CoQ10 levels were reduced in Parkinson's patients. They theorized that CoQ10 supplements might help preserve nerve cell function.

Patients studied had early-stage Parkinson's and took a placebo or CoQ10 intdoses of 300 milligrams, 600 mgs or 1,200 mgs daily. Their symptoms were evaluated for up to 16 months. By the eighth month, the 23 patients on the highest dose showed significantly less impairment than did the others.

Shults said if CoQ10 had merely eased symptoms, the differences probably would have appeared early on, which did not happen.

Side effects, including back pain, headaches and dizziness, were mostly mild.

The results indicate that follow-up research at perhaps even higher doses should proceed "pretty aggressively," said Dr. Bernard Ravina of the National Institute of Neurological Disorders and Stroke, which funded the study.

Copyright 2002 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.