Researchers in 10 hospitals across the United States tested the compound, called coenzyme Q10, in 80 patients who were in the early stages of Parkinson's.
After 16 months, the study found patients taking the highest dose of coenzyme Q10 had 44 percent less decline in their ability to carry out activities of daily living, including dressing, bathing and walking.
However, doctors caution it's too soon to recommend coenzyme Q10 to patients with Parkinson's.
"While it is tremendously encouraging that our results indicate that it is likely that coenzyme Q10 slows the progression of Parkinson's disease, our study did not have sufficient numbers of patients to unequivocally prove that it does," says Dr. Clifford Shults, the study's principal investigator and a professor of neurosciences at the University of California, San Diego. "It would be premature to recommend that patients with Parkinson's disease take high doses of coenzyme Q10."
Dr. Joel Perlmutter, a Parkinson's expert and professor of neurology, radiology and neurobiology at Washington University in St. Louis, made that point even more strongly.
"My father has Parkinson's, and I'm telling him not to take it," says Perlmutter, whose hospital was one of the centers involved with the study. "The findings are suggestive but not conclusive. Larger studies may demonstrate an unexpected result. There could be an adverse effect, although we haven't seen any evidence of that yet."
Coenzyme Q10 is classified as a dietary supplement and is therefore not regulated by the U.S. Food and Drug Administration. It's sold in various forms, including as a toothpaste additive, at health food stores.
However, the versions of the coenzyme Q10 sold in stores may differ and might not contain beneficial amounts of the compound, Shults says. Furthermore, it's very costly, he adds.
Another consideration: The people in the study had early-stage Parkinson's. None of the patients were taking any other Parkinson's medication, and nothing says coenzyme Q10 is beneficial for people with later stages of Parkinson's, he says.
The study appears in tomorrow's issue of the Archives of Neurology, and the researchers made a presentation today at the annual meeting of the American Neurological Association in New York City.
Parkinson's is a degenerative brain disease that affects about 1 percent of Americans over age 65. Symptoms include tremors, slowness of movement and muscle stiffness to the point of paralysis. Some patients also develop problems with sleeping, swallowing, depression and a decline in mental function.
Certain drugs, including levodopa, can reduce symptoms of Parkinson's disease, but no drug has been shown to slow the progressive deterioration in function.
The exact cause of Parkinson's in unknown, although it results from a loss of brain cells that produce the neurotransmitter dopamine.
What does coenzyme Q10 have to do with it?
Coenzyme Q10 is a molecular compound found in the mitochondria, a long, oval-shaped part of cells that convert nutrients into energy. Coenzyme Q10 is also a potent antioxidant.
Previous research by Shults and his colleagues has shown that people with Parkinson's have low levels of coenzyme Q10 and that the function of mitochondria is impaired.
In the current study, 80 patients were randomly assigned to one of four groups: those taking four doses of coenzyme Q10 that added up to 300, 600, or 1,200 milligrams a day, and those taking a placebo.
Study participants had a thorough physical exam and medical history taken before taking the coenzyme Q10.
They were then re-examined at regular intervals for up to 16 months, or until it was determined they needed to begin taking medication such as levodopa for the treatment of symptoms.
The eight-month exam was when the differences between the groups really began to show. Those on the highest dosage of coenzyme Q10 showed fewer declines in their physical abilities, mental function and mood. Those taking lower doses of coenzyme Q10 didn't do as well, but they did better than those on the placebo.
The benefit was seen throughout the 16 months of the study.
Shults believes coenzyme Q10 was doing more than just relieving the symptoms. If that was the case, he says, the groups taking the coenzyme Q10 would have shown improvement at the first check-up, one month into the study.
Since it wasn't until eight months into the study that the differences in the groups became apparent, Shults believes the coenzyme Q10 could be stopping Parkinson's march. "It suggests it may be possible to actually slow the progression of the disease rather than just treat the symptoms," he says.
Researchers are now seeking funding for a larger clinical trial to study the effects of dosages of 1,200 milligrams a day of coenzyme Q10 and greater.
"The value of this study is to lay the foundation for a subsequent larger study," Perlmutter says. "It's exciting. I'm enthusiastic about doing a real trial now to really find out if this stuff has benefit. It's a big step, but it's not the final step."
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